Token Passing-Typing Reperforator

Token Passing-Typing Reperforator

Token Passing

A method whereby each device on a local area network receives and passes the right to use the single channel on the LAN. The key to remember is that a token passing, or token ring LAN has only one channel. It's a high-speed channel. It can move a lot of data. But it can only move one "conversation" at a time. The Token acts like a traffic cop. It confers the privilege to send a transmission. Tokens are special bit patterns or packets, usually several bits in length, which circulate from node to node when there is no message traffic. Possession of the token gives exclusive access to the network for transmission of a message. The token is generated by one device on the network. If that device is turned off or fails, another device will assume the token creation task. When the package of token and message reaches its destination, the computer copies the message. The package is then put back on the network where it continues to circulate until it returns to the source computer. The source computer then releases the token for the next computer in the sequence.

With token passing it is possible to give some computers more access to the token than others. Usually one device on the network is designated the token manager. It generates the token. If that device is turned off or fails, another device will assume management of the token. There is a complicated sequence of events that result in the generation of a token and that deal with the eventuality of token loss or destruction. The logic for this process is built into token ring cards that fit inside computers. In some manufacturers' products, the logic is slightly different and can cause incompatibilities. See Token, Token Ring and Token Ring Packet.

Token Ring

A ring type of local area network (LAN) in which a supervisory frame, or token, must be received by an attached terminal or workstation before that terminal or workstation can start transmitting. The workstation with the token then transmits and uses the entire bandwidth of whatever communications media the token ring network is using. A token ring is a baseband network. Token ring is the technique used by IBM, Arcnet, and others. A token ring LAN can be wired as a circle or a star, with all workstations wired to a central wiring center, or to multiple wiring centers. The most common wiring scheme is called a star-wired ring. In this configuration, each computer is wired directly to a device called a Multi-station Access Unit (MAU). These are usually grouped together in a wiring closet for convenience. The MAU is wired in such a way as to create a ring between the computers. If one of the computers is turned off or breaks or its cable to the MAU is broken, the MAU automatically recreates the ring without that computer. This gives token ring networks great flexibility, reliability, and ease of configuration and maintenance.

Despite the wiring, a token ring LAN always works logically as a circle, with the token passing around the circle from one workstation to another. The advantage of token ring LANs is that media faults (broken cable) can be fixed easily. It's easy to isolate them. Token rings are typically installed in centralized closets, with loops snaking to served workstations. Some other LANs require your going up in the ceiling or into walls and finding coax taps. All the work on a token ring can be done on one or several panels. These panels allow you to isolate workstations, and thus isolate faults.

Token Ring LANs can operate at transmission rates of either 4M bits per second or 16M bits per second. The number of computers that can be connected to a single Token Ring LAN is limited to 256. The typical installation is usually less than 100. Large installations connect multiple token ring LANS with bridges. The theoretical limit of Ethernet, measured in 64 byte packets, is 14,800 packets per second (PPS). By comparison, Token Ring is 30,000 and FDDI is 170,000. See FDDI-II and FDDI TERMS. Help on this definition courtesy Tad Witkowicz of Crosscomm, Marlboro, MA, Tim Becker, Lanquest Group , Santa Clara, CA and Elaine Jones, VP Marketing, Coral Network Corporation, Marlborough, MA. See also Bridge, IBM Token Ring, MAU, Token Passing, Token Ring, Token Ring Card and Token Ring Packet.

Token Ring Card

Name given to the circuit board inserted into a computer device for connection to a token ring LAN. This board provides the physical connection to the LAN. It also participates in the collective management of the token by sending various messages to other token ring cards. Usually, one token ring card on the network is designated the token manager. It automatically generates a token as soon as it discovers one is missing, often with the help of other token ring cards. The sending of messages between token ring cards can be used to gather information about what is taking place on the network.

Statistics may be collected. These may indicated that the network should be altered in some way to improve performance. This management capability is a distinct advantage of token ring LANs. One possible drawback is that various manufacturers' token ring cards may differ slightly in how they implement token management, thereby making them incompatible in certain management features. Virtually all token ring cards will work together in basic token passing.

Token Ring Lan Service Unit

The ATM TLSU provides a powerful tool for offering internetworking services over ATM networks. Emulated token rings consist of up to 64 TLSU token ring ports located anywhere in the ATM network, interconnected with PVCs. These emulated token ring networks can be completely isolated form one another to ensure security and fairness among the attached LANs. The TLSUs are designed for flexible deployment, either local to an ATM switch or at a remote site. See ATM Ethernet LAN Service Unit.

Token Ring Packet

Packets on a token ring network are made up of nine fields: starting delimiter, access control, frame control, destination address, source address, routing information, the data, frame check sequence, and ending delimiter .

Starting Delimiter (SD): This is an 8-bit binary (1s and 0s) sequence which marks the beginning of a data packet.

Access Control (AC) and Frame Control (AC): These are two 8-bit sequences that are used by the computers for maintenance purposes.

Destination Address (DA): This is a 48-bit sequence that uniquely identifies the physical name of the computer to which the data packet is being transmitted. Each computer on a ring examines this field to determine if the packet is for it.

Source Address (SA): This is a 48-bit sequence that uniquely identifies the physical name of the computer that send the data packet. This is used by the receiving computer to formulate its acknowledgement .

Routing Information (RI): This is a variable-length sequence used if the data packet is being sent to a computer located on another token ring LAN. (This information can make it impossible for some bridges to route some packets. See Bridge.)

Data: This is a variable-length sequence (up to 17,800 bytes) that is the actual data being sent from source to destination.

Frame Check Sequence (FCS): This 32-bit sequence is used to protect the contents of the packet from being corrupted during transmission. See Frame Check Sequence.

Ending Delimiter (ED): This is an 8-bit sequence that signals the end of a packet.

Token Tree LAN

A type of local area network with a topology in the form of branches interconnected via active hubs. Using a token-passing scheme, the active hubs grant nodes access to the medium. See Token Packet.


The Apple Macintosh implementation of the Token Ring local area network.

Toll Booth Model

When there's no front-end fee to sign up and you pay every time you use ” just like on a highway. You don't pay an "installation" fee every time you hit the highway. You just pay tolls as you use the highway . Thus, some software companies would prefer to charge according to the "toll booth model."

Toll Bypass

When you dial a long distance phone call the traditional way ” on the PSTN ” the public switched telephone network, you're making a toll call for which you're charged a per minute price instead of a flat rate per month price. When you make that call some other way ” e.g. over your firm's private leased line network or over the Internet, you're bypassing the toll system, thus doing what's known as "toll bypass."

Toll Call

A call to any location outside the local service area. A long distance call.

Toll Center

  1. A central office where operators (human or mechanical) are present to assist in completing incoming toll calls.

  2. Name of a Class 4 switching center in the original Bell DDD hierarchy of long distance switching centers, providing links to the local exchanges of a city or metropolitan area; the point of interconnection between local networks and intercity networks.

Toll Connecting Trunk

A trunk used to connect a Class 5 office (local central office) to the direct distance dialing network.

Toll Denial

Permits phone user to make local calls but denies completion of toll calls or calls to the toll operator without the assistance of the attendant. See Toll Restriction.

Toll Diversion

A system service feature by which users are denied the ability to place toll calls without the assistance of a human attendant. Toll diversion affects the entire switching system instead of discriminating between individual extensions.

Toll File Guide

According to Bell Atlantic, a Toll File Guide is a number that was 'inherited' by a long distance carrier after divestiture. The RBOC retains a reference to the number and will show the number on a phone bill; however any billing associated with this number comes from the LD carrier. A toll file guide exists for purposes of number portability.

Toll Fraud

Theft of long distance service. Today's most common forms of toll fraud are DISA, voice mail and shoulder surfing. According to John Haugh of Telecommunications Advisors in Portland, OR, there are three distinct varieties of toll fraud:

"First Party" Toll Fraud, which is helped along by a member of the management or staff of a user. An example would be the telecommunications manager at the Human Resources department of New York City (an "insider") who sold his agency's internal code to the thieves , who in turn ran up unauthorized long distance charges exceeding $500,000.

"Second Party" Toll Fraud, which is facilitated by a staff member or subcontractor of a long distance carrier IXCs, vendor or local exchange telephone company selling the information to the actual thieves, or their "middlemen." An example would be a "back office clerk" working for one of these concerns who sells the codes to others.

"Third Party" Toll Fraud is facilitated by unrelated "strangers" who, though various artifices, either "hack" into a user's equipment and learn the codes and procedures, or obtain the needed information through some other source, to commit Toll Fraud.

Toll Grade

This is a strange one. "Toll grade" describes what a circuit-switched, long distance phone call sounds like. In particular it means that the call doesn't have a delay or an echo. When the telephony world started going to IP ” meaning it became packet switched ” the first calls suffered delays and echoes. As IP calls got better they suffered fewer delays and fewer echoes, i.e. they began to sound more and more "toll grade."

Toll Grooming

See Grooming.

Toll Office

A central office used primarily for supervising and switching toll traffic.

Toll Plant

The facilities that connect toll offices throughout the country.

Toll Quality

Imagine you get a good long distance telephone voice connection. You can hear them and they can hear you. That's a "toll quality" phone call. Most "toll quality" phone calls are made on a circuit-switched basis over the PSTN (Public Switched Telephone Network). When you make a phone call over the packet-switched public Internet, your conversation sounds pretty awful . It's not "toll quality." Some of the newer packet-switched networks, however, support voice that sounds pretty good ” even toll quality. Technically speaking, toll quality is defined in the ITU-T P.800 specification " Methods for Subjective Determination of Voice Quality." P.800 involves the subjective evaluation of preselected voice samples of voice encoding and compression algorithms. The evaluation is conducted by a panel of "expert listeners" comprising a mixed group of men and women under controlled conditions. The result of the evaluation is a Mean Opinion Score (MOS) in a range from 1 to 5, with 1 being "bad" and 5 being " excellent ." P.800 defines toll quality as an MOS of 4.0. See also MOS, P.800, and P.861.

Toll Restriction

To curb a telephone user's ability to make long distance calls. Toll restriction capability on modern PBXs and key telephone systems has been increasing in sophistication. Some PBXs now allow selective restriction based on specific extensions, users or geography. In other words, Joe Smith, the president, could call everywhere. John Doe in accounting might only be allowed to call Chicago and Houston, where our two factories are located. Mary Johnson, the seller for the western U.S., might only be allowed to call Denver and points west. There's considerable debate as to how useful toll restriction really is.

Toll Saver Feature

Many answering machines ” both PC based and stand alone machines ” allow you, the owner, to dial in and remotely retrieve your messages. Because it makes no sense to incur toll call costs if there are no messages, many machines have "a toll saver feature." They will only answer the first message on the fourth ring. They answer each additional one on the second ring. This means if you're calling remotely, you can count the rings. If you get to three rings and the machine hasn't answered , you know that there are no new messages (i.e. ones you haven't heard ) and you can safely hang up without incurring any toll costs.

Toll Station

A Telco phone from which established long distance message rates are charged for all messages sent over company lines.

Toll Switching Trunk

A trunk connecting one or more end offices to a toll center as the first stage of concentration for intertoll traffic. Operator assistance or participation may be an optional function. In U.S. common carrier telephony service, a toll center designated "Class 4C" is an office where assistance in completing incoming calls is provided in addition to other traffic; a toll center designated "Class 4P" is an office where operators handle only outbound calls, or where switching is performed without operator assistance.

Toll Testboard

Manual test position at which toll circuits are tested and repaired.

Toll Terminal

A phone only furnished with long distance service.

Toll Terminal Access

Allows hotel/motel guest phones to access toll calling trunks.

Toll Ticket

Ticket is the telephone company term for a bill. A toll ticket is a bill containing the calling number, called number, time of day, date and call duration. Some phone systems generate their own bills automatically. Some still need an operator. It depends on the equipment and the type of call.

Toll Trunk

A communications channel between a toll office and a local central office.

Toll-Free Call

See 800 Service.


See Telecom Operations Map.


An audio signal consisting of one or more superimposed amplitude modulated frequencies with a distinct cadence and duration. See Tone Set and Tones.

Tone Alternator

A motor-driven AC generator that produces audio-frequency tones.

Tone Dial

What the Australians call tone dial, Americans call touchtone. Tone dial or touchtone dial makes a different sound (in fact, a combination of two tones) for each number pushed . The correct name for tone dial is "Dual Tone MultiFrequency" (DTMF). This is because each button generates two tones, one from a "high" group of frequencies ” 1209, 1136, 1477 and 1633 Hz ” and one from a "low" group of frequencies ” 697, 770, 852 and 841 Hz. The frequencies and the keyboard, or tone dial, layout have been internationally standardized, but the tolerances on individual frequencies vary between countries . This makes it more difficult to take a touchtone phone overseas than a rotary phone.

You can "dial" a number faster on a tone dial than on a rotary dial, but you make more mistakes on a tone dial and have to redial more often. Some people actually find rotary dials to be, on average, faster for them. The design of all tone dials is stupid. Deliberately so. They were deliberately designed to be the exact opposite (i.e. upside down) of the standard calculator pad, now incorporated into virtually all computer keyboards. The reason for the dumb phone design was to slow the user's dialing down to the speed Bell central offices of early touch tone vintage could take. Today, central offices can accept tone dialing at high speed. But sadly, no one in North America makes a phone with a sensible , calculator pad or computer keyboard dial. On some telephone/computer workstations you can dial using the calculator pad on the keyboard. This is a breakthrough . It is a lot faster to use this pad. The keys are larger, more sensibly laid out and can actually be touch-typed (like touch-typing on a keyboard.) Nobody, but nobody can "touch-type" a conventional telephone tone pad. A tone dial on a telephone can provide access to various special services and features ” from ordering your groceries over the phone to inquiring into the prices of your (hopefully) rising stocks.

Tone Disabling

A method of controlling the operation of communications equipment by transmitting a certain tone over the phone line.

Tone Diversity

A method of Voice Frequency Telegraph (VFTG) Transmission wherein two channels of a 16-channel VFTG carry the same information. This is commonly achieved by twinning the channels of a 16-channel VFTG to provide eight channels with dual diversity.

Tone Generator

A handheld device which puts a tone on a cable. The tone is picked up with an inductive amplifier at connection points or the other end of the cable. Slang for the tool is Toner. See Inductive Amplifier and Tone Probe.

Tone Probe

A testing device used to detect signals from a tone generator to identify phone circuits, often the size of a fat pencil or skinny banana . Some models contain speakers ; others must be used with a headset or a butt set. See also Tone Generator.

Tone Ringing

Either a steady or oscillating electronic tone at the phone to tell you someone is calling.

Tone Sender

  1. A printed circuit card in Rolm CBX which supplies the data bus with the digital representations of the following tones: dial, ring, busy, error, howler (off-hook timeout) and pulse (after flashing).

  2. A printed circuit card which generates the following tones: dial, ring, busy, error, howler (off-hook timeout) and pulse (after flashing).

Tone Set

A collection of tones which are customarily used as a set for the purposes of call setup and teardown (e.g., DTMF, R1 MF, R2 MF). In the case of DTMF, the tone set can also be used by the client application during the conversation portion of a call.

Tone Signaling

The transmission of supervisory, address and alerting signals over a telephone circuit by means of tones. Typically inband. See also Signaling System 7.

Tone To Dial Pulse Conversion

Converts DTMF (Dual Tone Multiple Frequency) signals to dial pulse signals when trunks going to carry outgoing calls are not equipped to receive tone signals. A lot of electronic phones with touchtone dials have a sliding switch that allows you to choose whether the phone will outpulse in rotary, or whether it will touchtone out. You choose whichever your trunk line will accept.

Tone/Pulse Switchable

Most phones in North America come with a pushbutton dial. Many of these phones have a switch that says "Tone/Pulse." By sliding the switch one way, the pushbutton pad will dial by sending out touchtones. By sliding the switch the other way, the pushbutton pad will dial by rotary pulses . See Rotary Dial.


Tone generator used for identifying cable pairs.


There are four basic tones which you will hear as you use the telephone. These tones are used to indicate what's going on.

  1. Dial tone (also called dialing tone in Europe) is typically a continuous low frequency tone of around 33 Hz depending upon the telephone company. It indicates that the line is ready to receive dialing.

  2. Busy Tone when the line or equipment is in use, engaged or occupied. This is typically 400 Hz 0.75 sec on and 0.75 sec off.

  3. Ring Tone is typically 133 Hz make and break 0.4 sec On: 0.2 sec Off: Indicates called line is ringing out (17 Hz intermittent applied at called end to operate the telephone bell or buzzer).

  4. Number Unobtainable continuous at 400 Hz indicates out of service or temporarily suspended . Tones vary considerably from country to country and between telephone companies.


The unit of measurement used in air conditioning systems to describe the heating or cooling capacity of a system. One ton of heat represents the amount of heat needed to melt one ton (2000 lbs.) of ice in one hour . 12,000 Btu/hr equals one ton of heat. My office is on a 5,000 square foot floor. We use a ten ton air conditioner. It works most days. I wouldn't put more in. It would be a waste.


In some computer languages, a small program executed as a shell command. In other computer languages, such as BASIC, it is called a "utility."


A series of shortcut buttons providing quick access to commands. Usually located directly below the menu bar. Not all windows have a toolbar.


A Dialogic word for an Applications Generator.

Toolkit Developer Program

A strategic alignment by Dialogic with suppliers of voice processing applications development software to provide high-level application development tools.

Tone Dialing

Same as touchtone dialing. See Touchtone.


  1. See Technical Office Protocol.

  2. Task Oriented Practice/Processes. Step-by-step procedure for engineering, ordering, installing, provisioning, operating, maintaining, testing and repairing Materiel and Licensed Software. The flow-chart system organizes information to permit the completion of a specified task and leads the user through the task in a step-by-step fashion. A TOP leads the user from an initial stimulus to all operations required to correct the problem. This procedure allows subscribers at all levels of expertise to progress at their own pace in the performance of routine and acceptance type tasks . According to my friend, Larry Morey, "This is a telecom or software user guide for call center workers, operations centers tech/ engineers and on site support personnel. It is similar to a Method of Procedure (MOP). We (Qwest) ask our suppliers to provide us this documentation so we can test it in the lab then pass it on to our technicians and OPS folks. The uses of TOP ” Patch installations, card/circuit packet change-outs, how to provision a customer on a device, how to perform/install routing tables into a device, how to turn-up a device for the first time, testing/certifying a new software load/patch, testing and certifying a new device in the network."

Top Down

This is a method of distributing incoming calls to a bunch of people. It always starts at the top of a list of agents and proceeds down the list looking for an available agent. See also Round Robin and Longest Available.

Top Level Domain

A certain segment of a network in the Transmission Control Protocol/Internet (TCP/IP) UNIX environment. A network is segmented into a hierarchy of domains or groupings. In the Internet in the United States, there are six top-level domains: com (commercial organizations), edu (education organizations), gov (government agencies), mil (Military milnet hosts ), net (networking organizations), and org ( nonprofit organizations). The next lower level relates to specific companies, and the level below to devices within a company.


Network Topology. The configuration of a communication network. The physical topology is the way the network looks. LAN physical topologies include bus, ring and star. WAN physical topology may be meshed, with each network node directly connected to every other network node, or partially meshed. The logical topology describes the way the network works. For example, a 10Base-T LAN looks like a star, but works like a bus.

Topology Aggregation

The process of summarizing and compressing topology information at a hierarchical level to be advertised at the level above.

Topology Attribute

A generic term that refers to either a link attribute or a nodal attribute.

Topology Constraint

An ATM term. A topology constraint is a generic term that refers to either a link constraint or a nodal constraint.

Topology Database

As an ATM term, it is the database that describes the topology of the entire PNNI routing domain as seen by a node.

Topology Metric

A generic term that refers to either a link metric or a nodal metric.

Topology State Parameter

A generic term that refers to either a link parameter or a nodal parameter.


  1. Traffic Operator Position System. A specialized console designed for telephone company operators to help them complete toll calls.

  2. A computer operating system, which originally stood for the transcendental operating system.

  3. The operating system used by Digital Equipment Corp.'s DECSYSTEM-10 and DECSYSTEM-20 computers. These computers have been discontinued, but many are still in use.


Nortel Networks' Traffic Operator Position System designed on a token ring for interface between operator positions and the IBM Directory Assistance system database.

Torn Tape Relay

An antiquated tape relay system in which the perforated tape is manually transferred by an operator to the appropriate outgoing transmitter. In short, it's a torn tape relay is a store and forward message switching system which uses punched paper as the storage medium.


Type of Service.

Total Available Market

See TAM.

Total Cost of Ownership.

See TCO.

Total Harmonic Distortion

The ratio of the sum of the powers of all harmonic frequency signals (other than the fundamental) to the power of the fundamental frequency signal. This ratio is measured at the output of a device under specified conditions and is expressed in decibels.

Total Internal Reflection

The reflection that occurs when light strikes an interface at an angle of incidence (with respect to the normal) greater than the critical angle.

Total Network Data System.

TNDS. A telephone company term. The Total Network Data System is the overall data system for all types of switching equipment.

Total Service Resale

TSR. The complete resale, on a wholesale basis, of an ILEC's network and services. This allows a competitor to enter a market without deploying network infrastructure. Prices charged by the ILEC for TSR are based on avoided costs, the costs incumbents avoid in selling on a wholesale versus retail basis.

Total Transaction Call Processing

A Rockwell term. Rockwell's philosophy. It guides their approach to call centers. It involves managing the success of a call center, not merely supplying the ACD (Automatic Call Distributor). It could include software development, CTI integration, network management, consulting services, IVR and voice processing systems. Rockwell says it will act as the prime contractor or as a single provider for a call center solution.


Touchtone is not a trademark of AT&T, despite what editions one through six of Newton's Telecom Dictionary said. It is a generic term for pushbutton telephones and pushbutton telecommunications services and the term "touchtone" may be used by anyone . At one stage it was a trademark of AT&T. At divestiture in 1984, AT&T gave it to the public. And that's who owns it now. The public. If you don't believe this, call Frank L. Politano, AT&T Trademark and Copyright Counsel, in Basking Ridge, New Jersey. For a full explanation of touchtone, see DTMF, which stands for Dual Tone Multi Frequency signaling, i.e. touchtone.

Touchtone Adaptor

A device that can be connected to a rotary dial telephone to allow for DTMF signaling.

Touchtone Signal to Dial Pulse Conversion

Converts touchtone dial signals to dial pulse (rotary) signals when the serving central office of the distant end of outgoing trunks is not equipped to receive touchtone signaling. External conversion equipment is not needed for this feature. Obsolete term. All central offices will accept touchtones these days.

Touchtone Type Ahead

Also known as DTMF Cut-Through. Touchtone Typed Ahead is the ability of a voice response system to receive DTMF tones while the voice synthesizer is delivering information, i.e. during speech playback. This capability of DTMF cut- through saves the user waiting until the machine has played the whole message (which typically is a menu with options). The user can simply touchtone his response anytime during the message ” when he first hears his selection number, when the message first starts, etc. When the voice processor hears the touchtoned selection (i.e. the DTMF cut- through), it stops speaking and jumps to the chosen selection. For example, the machine starts to say, "If you know the person you're calling, touchtone his extension in now." But before you hear the "If you know" you push button in 230, which you know is Joe's extension. Bingo, the message stops and Joe's extension starts ringing.


People who take training classes just to get a vacation from their jobs. "We have about three serious students in the class. The rest are tourists."


  1. A name for a PC in a vertical or upright case. Tower PCs (if they're correctly designed) have a big benefit. Heat rises and escapes more easily than in traditional horizontal machines. Heat and power surges are the most damaging threats to PC.

  2. A structure used for mounting antennas. Towers may be classified ways: by (1) mounting system (self supported or guyed); (2) shape ( triangular , square, or pole); (3) erection method (crank-up, tilt-over, or erected sectionals); and (4) weight and height (heavy or light).

Tower Ads

See Skyscraper Ads.

Tower Marking

Tower lighting or painting with specific patterns so that the tower can be easily seen by aircraft pilots.


  1. Abbreviation for Transport Protocol or Twisted Pair.

  2. Test Point.

  3. Transition Point. A location in the horizontal cabling subsystem where flat undercarpet cabling connects to round cabling.

TP1, TP2, TP3, TP4, TP5

The various service levels of the ISO IS 8073 Transport Protocol. TP4 is the most popular service level for information system networks and is specified in the U.S. government GOSIP architecture. TP4 stands for OSI Transport Protocol Class 4 (Error Detection and Recovery Class). This is the most powerful OSI Transport Protocol, useful on top of any type of network. TP4 is the OSI equivalent to TCP.


Transport Protocol 4. An OSI layer-4 protocol developed by the National Bureau of Standards. See TP1.


A term given to the ISO protocol suite that closely resembles TCP/IP.


Twisted-Pair Media Interface Connector: This refers to the connector jack at the end user or network equipment that receives the twisted pair plug.


Twisted-Pair Physical Media Dependent, Technology under review by the ANSI X3T9.5 working group that allow 100 Mbps transmission over twisted-pair cable. Also referred to as CDDI or TPDDI.


Terminal Packet Assembler/Disassembler linked to a cluster controller or terminal device, taking native protocol input and converting it to X.25 for transmission over a packet network.


  1. TOPS Position Controller.

  2. Transmission Power Control. See 802.11a.


The Trusted Computer Platform alliance. The TPCA ho;es to hammer out a specification that would include secure PC operating systems using a hardware security chip it has already specified.


Third Party Call Control: As an ATM term, it is a connection setup and management function that is executed from a third party that is not involved in the data flow.


Twisted Pair Distributed Data Interface. Also known as ANSI X3T9.5.-TPDDI. TPDDI is a new technology that allows users to run the FDDI standard 100 Mbps transmission speed over twisted-pair wiring. Unshielded twisted-pair has been tested for distances over 50 meters (164 ft.). TPDDI is designed to help users make an earlier transition to 100 Mbps at the workstation. Also known as CDDI, Copper Distributed Data Interface.


Abbreviation for Transport Protocol Data Unit.


Twists Per Foot.


Tracks Per Inch. A measurement of how much data can be stored on a disk.


Terminating Point Masterfile. A LEC system that tracks RAOs, NPAs, NXXs, among other things.


  1. Telephony over Passive Optical Network. A passive (i.e., with no active electronics) optical local loop which connects the subscriber premises to an all-fiber telecommunications network. See also APON and PON.

  2. OSI Transport Protocol Class O (Simple Class). This is the simplest OSI Transport Protocol, useful only on top of an X.25 network (or other network that does not lose or damage data).


  1. PVC Table.

  2. Third Party Verification. This term relates to a new FCC regulation (to prevent slamming) that requires an LOA or third party verification for all PIC changes on ANIs for a company's commercial customers, and TPV for all residential customers. Compliance was required as of 4/29/99.


Thin Quad Flat Pack, a format used in the design of PCMCIA devices. Another format is called PQFP, which stands for Plastic Quad Flat Pack.


Total Quality Management. Doing what management should have been doing all along.


  1. Trouble Report.

  2. Technical Reference.

  3. Technical Requirement. These publications are the standard form of Bellcore-created technical documents representing Bellcore's view of proposed generic requirements and standards for products, new technologies, services, or interfaces. What's the difference between TRs and GRs? I asked Irvin Bingham, He replied: In the good old days, AT&T and Bellcore issued Technical Requirements (TRs) to dictate the way things would work in "their" phone system. After the Telecommunications Act of 1996, TRs relating to competitive products and services became General Requirements (GRs). So in 1996, TR-303 became GR-303. Bellcore also set up GR "interest groups" to elicit industry participation in defining the specifications. Although Bellcore will listen to outside suggestions and opinions , I don't think Bellcore is obligated to act on any of them. Bellcore still has absolute control over their equipment interfaces to the outside world, but they are now required to publish those specifications and make them available to their competitors-for whatever price Bellcore wants to charge. An introduction to GR-303 is available online at Unfortunately, if you want a copy of any specification, you have to pay for it. After all, when did Bellcore ever give away anything to its competitors ? Bellcore even charges exorbitant membership fees (called industry funding) for the privilege of participating in a GR interest group. See GR-303, TR-303 and also ISDN.


A Bellcore (now Telcordia) standard describing a digital interface between the SLC-96 digital loop carrier system and a local digital switch.


A defacto standard published by Bellcore, now Telcordia. It amounts to an industry standard high level control interface to dumb switches. It also applies to Fiber In The Loop (FITL). See GR-303 for the full explanation.


A defacto standard published by Bellcore, now Telcordia, which spells out how the Bell regionals want long distance companies to connect to the Bell regionals' local networks. Several observers compare the TR-444 specs to simple direct dial long distance voice phone service.


A Bellcore (now Telcordia) standard describing a customer interface on a Digital Loop Carrier (DLC) or channel bank system and its relationship to the local digital switch. Recently it has been primarily associated with GR-303 or TR-008, and allows a standard POTS line to ring without interfering with derived voice (voice over broadband) lines. An example of implementation is standard POTS lines co-existing peacefully with derived voice lines on an ADSL modem. The 0-4 Khz frequency is used to carry standard POTS, while the remaining frequency band is used to support VoDSL as well as broadband data services.


Telecommunications Resellers Association. See ASCENT.


Technical Recommendations Approval Committee.

Trace Agent

This is a command used in the Infoswitch product line to report all the events and transactions an agent has been involved in over a defined period of time.

Trace Block

See Trailer.

Trace Packet

A special kind of packet in a packet-switching network which functions as a normal packet but causes a report of each stage of its progress to be sent to the network control center.

Trace Program

A computer program that performs a check on another computer program by showing the sequence in which the instructions are executed and usually the results of executing the instructions.

Trace Route

A software utility that traces a data packet from your computer to a distant Internet server. After you've sent the packet to the distant host, you get a report on your screen, which shows how many hops from router to router the packet requires to reach the host and how long each hop takes. If you're visiting a website and pages are appearing slowly, you can use trace route software to figure out where the longest delays are occurring, or worse , where the bottleneck is. The original trace route is a UNIX utility, but nearly all platforms have something similar. Windows includes a utility called "tracert." In Windows 95/98, you can run this utility by going Start>Run and then entering "tracert" followed by a space and then the domain name of the host. For example: tracert Trace route utilities work by sending packets with low time-to-live (TTL) fields. The TTL value specifies how many hops the packet is allowed before it is returned. When a packet can't reach its destination because the TTL value is too low, the last host returns the packet and identifies itself. By sending a series of packet and incrementing the TTL value with each successive packet (starting with one), a trace route finds out who all the intermediary hosts are.

Tracer Stripe

When more than one color coding stripe is required, the first or widest stripe is the base stripe. The other, usually narrower stripes are the tracer stripes .


Traceroute is software to help you figure out what's happening on your Internet connection. Traceroute is used to evaluate the hops taken from one end of a link to the other on a TCP/IP network, such as the Internet. Traceroute shows the full connection path between your site and another Internet address. It shows how many hops a packet requires to reach the host with the time required for the packet to get to each intermediate host or router. Traceroute is a more useful superset of PING.


Trace Route. A utility used on TCP/IP networks to trace the route that datagrams take between the server and another system. As tracert also tells you how long each hop takes, it can be a useful tool in identifying system trouble spots. See Trace Route.


  1. A storage channel on a disk or tape which can be magnetically encoded.

  2. On a data medium, a path associated with a single read/write head as data move past the head.

  3. Every time you write to a CD, you will create at least one track, which is preceded by a pre-gap and followed by a post-gap. Any session may contain one or more tracks, and the tracks within a session may be of the same of or different types (for example, a mixed- mode disc contains data and audio tracks).

  4. A process by which a receiver follows , or "locks onto" a received carrier frequency or clock rate.

Track Access Time

The time it takes to move the pickup head on a disk drive from one track to another.

Track Density

The number of tracks per unit length, measured in a direction perpendicular to the tracks.

Track Speed

The maximum speed which a train can travel over a section of railway tracks.


An upside-down MOUSE; a rotatable ball in a housing used to position the cursor and move images on a computer screen. A mouse needs desktop room to work, a trackball stays in one place, and can even be part of a keyboard or built into a laptop computer. It's hard to see why anyone uses a mouse instead of a trackball. This dictionary was typeset by a fine lady called Jennifer Cooper-Farrow, who used a trackball and a Macintosh computer.


  1. Figuring where a satellite is and keeping track of it. This is not an easy job, given the vastness of space.

  2. The effect created in compressed video when the speed of the transmission is not great enough to keep up with the speed of the action. Tracking creates a tearing effect on the video picture.

  3. A call center term. A software feature that models actual events and activities in your call center to aid you in short-term planning and evaluation of employee and call center performance. The tracking functions include employee information scheduling assignment, daily activity, and intra-day performance.

Tracking and Data Relay System



Terminal Radar Approach CONtrol. An installation in an airport or close to an airport from which approaching and departing aircraft are directed by people called controllers which sit in front of giant screens which show the movement of close aircraft. These controllers speak to the pilots in the planes instructing them where to move in order to avoid collisions and to land and takeoff safely.

Tractor Feeder

A device which attaches to a computer printer and allows the printer to use continuous, sprocket-fed, paper. Such paper has a row of evenly spaced holes on both sides. Those holes coincide with the pins on the tractor feeder. In all tractor-fed printers, the tractor moves the paper, not the printer's platen.

Trade Secret

A trade secret can be any information, knowledge, data, or the like which is useful in business and not commonly known. A trade secret is anything from a customer list to the formula for Coke syrup. Enforcing a trade secret, for example, in order to enjoin a former employee from working for a competitor normally requires proof that the secret allegedly taken was suitably identified as such, that the employee was subject to a written contract including an obligation of confidentiality, and that physical access to the secret was suitably restricted. See Intellectual Property.


A trademark can be any word, symbol, slogan , design, musical jingle, or the like capable of differentiating one party's goods or services from another's. The question is whether a member of the relevant segment of the public would be misled as to the source of the goods. Thus, a descriptive mark ("Frigidaire") is less powerful than a coined mark ("Xerox"), and the same mark can be used by different parties, if on differing goods ("Cadillac" for dog food versus "Cadillac" for automobiles.) The r symbol indicates that a mark has been registered by the Federal government, while the tm or sm symbols merely indicate that the user does not intend to waive his rights in the mark. It is not legally necessary to use the statements commonly seen that certain trademarks are the property of their owners , or to use the r symbol in text, but it does prevent any accusation of misappropriation. See Intellectual Property.

Trader Turret

A very large key telephone used by traders of commodities, securities, etc. Turrets typically have many line buttons. Each one corresponds to a trunk, an auto- dial or tie-line circuit to another trader or a financial institution. The objective of turrets is to allow the trader to be in instant communication with others who might want to buy or sell that which he is trying to sell or buy. See the June issue of TELECONNECT for an annual roundup of turrets.


Bellcore's definition: A flow of attempts, calls, and messages. My definition: The amount of activity during a given period of time over a circuit, line or group of lines, or the number of messages handled by a communications switch. There are many measures of "traffic." Typically it's so many minutes of voice conversation, or so many bits of data conversation. Note that Bellcore includes attempts in its definition of traffic. I don't. The decision is yours. But you should be aware of what you include in your calculations. See also Traffic Engineering and Queuing Theory.

Traffic Analysis

Inference of information from observable characteristics of data flow(s), even when the data is encrypted or otherwise not directly available. Such characteristics include the identities and locations of the source(s) and destination(s), and the presence, amount, frequency, and duration of occurrence.

Traffic Capacity

The number of CCS (hundred call seconds) of conversation a switching system is designed to handle in one hour. This is the simple definition. See Traffic Engineering.

Traffic Carried

See Traffic Offered and Carried.

Traffic Characteristic

A basic customer or network induced property of traffic that influences a load-service relationship. Peaked traffic, Poisson traffic, and smooth traffic are examples of traffic characteristics.

Traffic Concentration

The average ratio of the traffic during the busy hour to the total traffic during the day.

Traffic Data Administration System

TDAS. A telephone company term. The TDAS program merges the data from various data acquisition systems and performs the following functions: a. The establishment of schedules for data collection; b. Maintenance of assignments records for all data collection devices; c. The acceptance of measurement data for any time interval. d. The reporting of measurement data to downstream processes via a set of standard interfaces. e. Performance of quality control reports specifically designed to permit effective management of the data collection effort. f. Adjustment and validation of measurement data.

Traffic Data To Customer

The owner of a call accounting system can poll his PBXs daily or hourly and get traffic measurements, including peg counts, usage and overflow data. Summary reports, exception reports and complete traffic register outputs can be obtained.

Traffic Engineering

The science of figuring how many trunks, how much switching equipment, how many phones, how much communications equipment you'll need to handle the telephone, voice, data, image and video traffic you're estimating. Traffic engineering suffers from several problems:

  1. You are basing your future needs on past traffic.

  2. Most traffic engineering is based on one or more mathematical formulas, all of which approach but never quite match the real world situation of an actual operating phone system. Computer simulation is the best method of predicting one's needs, but it's expensive in both computer and people time.

  3. Many people in the telecommunications industry do not understand traffic engineering, have not worked with it sufficiently and make dumb and costly mistakes.

  4. Since there are now several hundred long distance companies in the United States, and several thousand differently-priced ways of dialing between major cities, traffic engineering has become very complex.

After I wrote the above definition, Lee Goeller, disagreed with me and contributed this definition.

Traffic Engineering: The application of probability theory to estimating the number of servers required to meet the needs of an anticipated number of customers. In telephone work, the servers are often trunks, and the customers are telephone calls, assumed to arrive at random (see POISSON Process). Then arriving calls, upon finding all trunks busy, vanish , a "blocked call cleared" situation obtains (see ERLANG B). When a call stays in the system for a given length of time, whether it gets a trunk or not, "blocked calls held" applies (see Poisson Distribution). If a call simply waits around until a trunk becomes available and then uses the trunk for a full holding time, the correct term is "blocked calls delayed" (See ERLANG C and Queuing Theory). Like any form of predicting the future on the basis of past behavior, traffic engineering has its limitations; however, when used by those who have taken the trouble to learn how it works, its track record is surprisingly good, and vastly better than most forms of simulation (see Simulation).

Traffic Engineering Tunnel

A label-switched tunnel that is used for traffic engineering. Such a tunnel is set up through means other than normal Layer 3 routing; it is used to direct traffic over a path different from the one that Layer 3 routing could cause the tunnel to take. See also Traffic Engineering.

Traffic Intensity

A measure of the average occupancy of a facility during a period of time, normally a busy hour, measured in traffic units (erlangs) and defined as the ratio of the time during which a facility is occupied continuously or cumulatively) to the time this facility is available. A traffic intensity of one traffic unit (one erlang) means continuous occupancy of a facility during the time period under consideration, regardless of whether or not information is transmitted. See also Traffic Engineering.

Traffic Load

Total traffic carried by a trunk during a certain time interval.

Traffic Measurement

Memory and other software in a telephone system which collect telephone traffic data such as number of attempted calls, number of completed calls and number of calls encountering a busy. The objective of traffic measurement is to enter the results into traffic engineering and so arrange one's incoming and outgoing trunks to get the best possible service. See Traffic Engineering.

Traffic Measurement and Recording Systems

TMRS. A computer generated report showing usage information of telephone systems. Usually this includes trunk utilization, outages, queuing time, and the need for additional common equipment.

Traffic Monitor

PBX feature that provides basic statistics on the amount of traffic handled by the system.

Traffic Offered And Carried

People pick up the phone and try to place their calls. This is "Traffic Offered" to the switch. The calls that get through the switch and onto lines is called "Traffic Carried." The difference between traffic offered and carried is the traffic that was lost or delayed because of congestion. There are two basic ways of measuring traffic ” erlangs and CCS (or hundred call seconds).

Traffic Order

TO. A telephone company term. These are requests originated by the Network Switching Engineering organization. The requests cover new systems or additions, removals and rearrangements to existing systems. The traffic order recommends types, quantities , and arrangements of local and toll equipment in accordance with the latest forecasts of trunks, network access lines and traffic studies.

Traffic Overflow

Occurs when traffic flow exceeds the capacity of a particular trunk group and flows over to another trunk group.

Traffic Path

A path over which individual communications pass in sequence.

Traffic Policing

Process used to measure the actual traffic flow across a given connection and compare it to the total admissible traffic flow for that connection. Traffic outside of the agreed upon flow can be tagged (where the CLP bit is set to 1) and can be discarded en route if congestion develops. Traffic policing is used in ATM, Frame Relay, and other types of networks. Also known as admission control, permit processing, rate enforcement, and UPC. See also tagged traffic.

Traffic Prioritization

Imagine your job is to run a University's data network. Everything is running smoothly. Your professors are checking research with their colleagues in other universities. Your students are submitting their papers and checking their email. Then suddenly your students discover Napster. And they start downloading zillions of bytes of music. The music traffic brings your network to its knees. Your solution? Traffic prioritization. Install some hardware and software which figures out which is the important traffic and let the important traffic through and hold back the unimportant traffic until the network is free. Like a very smart traffic cop. This equipment can get pretty complex. Here are some words from CheckPoint explaining their traffic prioritization product: "Rules are established for traffic control via a combination of traffic classifications and bandwidth control criteria. Network managers can classify traffic on the basis of Internet service or application (HTTP, FTP, Telnet, BackWeb), source, destination, group of users, groups of Internet services, Internet resource (ex. URL), and traffic direction ” inbound or outbound...Control criteria categories include:

"Weights ” Allocates bandwidth for users and Internet services based on designated merit or importance. The weight assigned to a particular class of traffic is proportionate to the weights of all other managed traffic."

"Guarantees ” Provides guaranteed bandwidth for critical applications or designated users and groups."

"Limits ” Sets bandwidth restrictions for discretionary network services or user applications which are not time sensitive."

Traffic Radar

A RADAR (RAdio Detecting and Ranging) device bounces a radio signal off of a moving object, such as a car. The reflected signal is picked up by a receiver. Traffic radar receivers measure the frequency difference between the original and reflected signals. This frequency difference is converted into a speed, which appears on the receiver's display. Radar signals, like other types of radio signals, travel in straight lines until they hit an object that either absorbs, reflects, or refracts the signal. Radar receivers cannot see around curves or over hills, so a vehicle must be in the receiver's line of sight for traffic radar to get a speed measurement. There are different radar speed detection systems:

  1. Continuous Wave (CW). This traffic radar system transmits constantly. The detector alerts you up to several miles from the radar source in optimum conditions.

  2. Triggered CW. Stationary Mode (also known as Instant-On, Laser Pulse, or Hawk) This system transmits radar signals in bursts, and requires less than one second to determine speed. The detector senses the burst and sounds a special signal up to several miles from the source. However, since the radar gun only transmits signals when the operator triggers it, the alert range depends on how often the operator triggers the gun.

  3. Triggered CW, Moving Mode, This system uses pulses to determine the police vehicle's speed. Then when the operator triggers the system, it transmits a signal burst to determine the speed of oncoming traffic. The detector senses both the police vehicle speed pulses and the triggered signal.

Traffic Recorder

A device which measures traffic activity on a transmission channel. It's a recorder, not a processor. It's dumb.

Traffic Register

A software area which records occurrences within a central office, such as peg count, overflow, all trunks busy, etc.. The types of occurrences measured vary widely according to the type of system.

Traffic Sensitive

A telephone company term. Applies to equipment whose ability to provide a specific level of service varies as the calling load varies.

Traffic Separations

Dave Holland send me this email: Dear Harry, I am a young central office technician for a rural independent Telco. A new assignment that was given to me is traffic separations. Until we got into the process quite a way I did not know what it was. I now understand it as the mapping of all the traffic through a switching device with incoming traffic being mapped to outgoing traffic and the place that they meet on the matrix is assigned a register. The register allows you to gather the information about all calls made between the two points. I wanted to look up the "official definition for Traffic Separations (TSEP) and looked to your book. To my utmost surprise I did not find it. I think it would be a good addition to your book because it is something that all telephone companies do or should be doing. It is not the same as just a peg count it is far more detailed and requires allot of work to get set up and then administer later on.

So I asked Dave to send me a definition. He send me one from a company called Network Services Group, It reads:

The Traffic Separations measurements are used to identify the proportion of jurisdictional usage for support of division of revenue studies. There are also secondary objectives of fulfilling federal and state regulatory requirements, as well as ownership and inter-/intra- company settlements. Usage is apportioned on the basis of relative minutes of use. These studies are normally on a monthly basis and seven consecutive days in duration. Data is collected and reported on a hourly and daily basis. In a Traffic Separations study the measurement data is collected on all switched traffic utilizing a separations matrix which correlates the "calling" and "called" party of each call. The mapping of a call on to the matrix is done with the INSEP value assigned to the "calling" party and the DESEP value assigned to the "called" party. The intersection of each INSEP/DESEP pair on the matrix is known as a cell. Each cell within the matrix is uniquely assigned to a register Each register consists of a peg counter and usage counter. Within the limits of allowed quantities of DESEPs, and INSEPs, line "class of service", incoming trunk group, outgoing route appearance, and terminating treatment call type can be uniquely assigned an INSEP or DESEP as appropriate. With the proper planning of INSEP/DESEP assignments and grouping of cell (s) to registers this can result in the data being collected on a "call type" basis. The value ranges for separations parameters are The type(s) of data to be obtained from a separation study is determined by a separation study administrator (a person or group of people in the operating company) who plan, setup and verify each study. In order to administer these "flexible" assignments all separation study parameters are administered using recent change commands. The capability to make and change assignments as well as display and validate assignments are part of the traffic separation administration process. The end product of the traffic separations feature is a set of reports for telcos which are used for statutory division of revenue purposes and for spot traffic studies.

Traffic Service Position System

TSPS. A toll switchboard position configured as a push button console.

Traffic Shaping

Traffic shaping is a phrase that describes a technique to control the rate of specific traffic types that will be allowed onto the network. Traffic shaping is a generalized term for a congestion control management procedure in which data traffic is regulated in order that it conform to a specified, desirable behavior pattern. This becomes important at locations in the network that present bottlenecks. Take the analogy of Atlanta airport. If other airports allowed planes to come to Atlanta faster than they could land, they would have to be put in holding "Queues" awaiting their turn. Some may get low on fuel and have to return to another airport, only to return to Atlanta again later adding to the congestion. If the air traffic that was permitted to arrive in the Atlanta airspace was slowed or delayed such that it did not exceed the landing capacity, then the air traffic would have been "shaped" to fit the landing capacity. This is essentially the technique of traffic shaping. But then there are more important and less important planes arriving. Using traffic shaping rules, network managers can allocate bandwidth to mission-critical user applications to ensure those applications receive the bandwidth required for efficient operation. VoIP is one application where traffic shaping is particularly useful. Network managers can identify, prioritize, and control traffic on their Frame Relay networks on a per application and per PVC basis. Shaping is accomplished by controlling the source of the traffic, not by just using queues. Traffic shaping may include reduction or elimination of excessive traffic bursts from a LAN as it is presented to a Frame Relay WAN through a router. Such bursts may exceed the CIR (Committed Information Rate) and, therefore, be marked DE (Discard Eligible). During periods of Frame Relay WAN congestion, such bursts may result in discarded frames , which require retransmission. Should the excessively long bursts be transmitted successfully across the Frame Relay WAN, surcharges may apply (such surcharges are unusual for U.S. carriers ). All things considered , traffic shaping may be the best approach in such a scenario. In an ATM LAN environment, traffic shaping responsibility can be accomplished by the ATM switch, which actively would alter the traffic characteristics of a cell stream on a VCC (Virtual Channel Connection) or VPC (Virtual Path Connection). This procedure may serve to reduce the peak cell rate, limit the burst length, or minimize the cell delay variation by re-spacing the cells in time in order that traffic flow not congest the switch. This can be particularly important when dealing with long bursts of high priority traffic, as such traffic literally can bring the rest of the user traffic flow to its knees. See also ATM, Committed Information Rate, Discard Eligible, Frame Relay, VCC and CPC.

Traffic Table

A computer database into which a PBX enters a count of feature activity. Certain detected operating errors are also entered in the traffic table.

Traffic Theory

The branch of probability theory used to predict how many telephone lines you need for how much traffic you are likely to put on the lines.

Traffic Usage

Total occupancy of a network. This is calculated a the product of holding time and calling rate and can be expressed as call-hours. Traffic usage may be made up of many short calls or few long calls ” it doesn't matter.

Traffic Usage Recorder

A device for measuring and recording the amount of telephone traffic carried by a group, or several groups, of switches or trunks.

Traffic Use Code

A telephone company definition. A system standard two character alpha code designating the type of traffic offered to a trunk group. Traffic Use Codes are listed and defined in Section 795-400-100 (Common Language Circuit Identification ” Message Trunks).


As an ATM term, it is an entity that transfers information provided by a client layer network between access points in a server layer network. The transported information is monitored at the termination points.


  1. A nonstandard way of standard way of sending data. Trailers are used on some networks by 4BSD UNIX and some of its derivatives.

  2. A block of controlling information transmitted at the end of a message to trace error impacts and missing blocks. Also referred to as a trace block.


  1. When a modem "trains," it's establishing connectivity with the inbound RTS/CTS transaction. See also RNA.

  2. The creation of word reference data by presenting words to a recognizer. A voice recognition term.


A feature of some modems which adjust to the conditions including amplitude response, delay distortions, timing recovery, and echo characteristic, of a particular telecommunications connection by a receiving modem. See Training Up.

Training up

A technique that adjusts modems to current telephone line conditions. The transmitting modem sends a special training sequence to the receiving modem, which makes necessary adjustments for line conditions.


  1. It is a completed event that can be assembled in chronological sequence for an audit trail.

  2. An entry or an update in a database.

Transaction Capabilities

Function that controls non-circuit- related information transfer between two or more nodes via a SS7 signaling network.

Transaction Capabilities Application Part

TCAP. The application layer protocol of SS7. Transaction capabilities in the SS7 protocol are functions that control non-circuit related information transferred between two or more signaling nodes. Definition from Bellcore in reference to its concept of the Advanced Intelligent Network.

Transaction Detail

The detail of a transaction record.

Transaction Engines

If you sell on your site, you need an application that allows the customer to configure an order and pay by credit card or other means. These systems let you manage product and buyer information, and usually link to third parties that process the credit-card transactions. These are called transaction engines.

Transaction Internet Protocol

TIP. The Transaction Internet Protocol protocol ensures that multivendor transaction monitors will work with one another to complete transactions over the Internet (RFC 2371). TIP came from a joint Microsoft/Tandem effort. I excerpted the following from a Microsoft Market Bulletin.

Two companies (Microsoft and Tandem) team have combined to publish a specification for a two-phase commit protocol to make it easier for businesses to do transaction processing across the Internet. Two-phase commit is the commonly-used application protocol used by high-end system software ” including Transaction Processing (TP) Monitors and databases ” to coordinate the work of multiple applications on different computers as a single unit, or transaction. Businesses want to link existing transaction processing systems together across the Internet using two-phase commit protocols, but existing implementations of two-phase commit are too complex for use on the Internet. TIP is designed to solve this problem, defining a simple protocol that existing vendors of TP Monitors and databases can easily implement into their products, solving the problem of transaction coordination across the Internet. Microsoft will implement TIP in the Distributed Transaction Coordinator (DTC), Microsoft's transaction manager that first shipped with SQL Server 6.5. DTC currently supports other open two-phase commit protocols, including OLE Transactions, the X/ Open 's XA protocol, and has future plans to support SNA LU 6.2 Sync Level 2. Windows NT Server 5.0 will provide native support for TIP. Tandem will support TIP in its NonStop systems. Both the reference implementation and the TIP specification can be downloaded directly from or Microsoft and Tandem have submitted the TIP specification to the Internet Engineering Task Force, who have published it at .

Transaction File

A collection of transaction records. A transaction data entry program allows for the creation of new transaction files used to update the data base.

Transaction Link

Rockwell's link from its Galaxy ACD to an external computer. See Open Application Interface.

Transaction Tracking

Your software keeps track of each transaction as it happens. And if a component of your network fails, your transaction tracking software backs out of the incomplete transaction. This allows you to maintain your database's integrity. You may, however, lose the single transaction you were working on when your network got sick.

Transaction Processing

A processing method in which transactions are executed immediately when they are received by the system, rather than at some later time as in batch-processing systems. Airline reservation databases and automatic teller machines are examples of transaction-processing systems.

Transactional Integrity

A term that describes how your computing/telecom system handles making sure that the transaction you just made is solid and clean and that the next time you want to get to the results of the transaction you can. "Transactional integrity" becomes critical when you're storing bits and pieces of your transactions on different media, in different places. For example, you might want to store your data on a magnetic hard drive and your associated images on a separate optical drive.

Transborder Data Flow

TDF. Transborder data flows are movements of machine-readable data across international boundaries. TDF legislation began in the 1970s and has been put into effect by many countries in an attempt to protect personal privacy of citizens . This term has particular meaning as it relates to electronic commerce or EDI and is becoming more and more relevant with the use of the Internet as a means to conduct global business.


  1. Any device that transmits and receives. In sending and receiving information, it often provides data packet collision detection as well.

  2. In IEEE 802.3 networks, the attachment hardware connecting the controller interface to the transmission cable. The transceiver contains the carrier-sense logic, the transmit/receive logic, and the collision-detect logic.

  3. A device to connect workstations to standard thick Ethernet-style (IEEE 802.3).

Transceiver Cable

In local area networks, a cable that connects a network device such as a computer to a physical medium such as an Ethernet network. A transceiver cable is also called drop cable because it runs from a network node to a transceiver (a transmit / receiver) attached to the trunk cable. See Transceiver.


A device that combines two 1.544 megabit per second bit streams into a single 1.544 megabit per second bit stream to enable transmission of 44 or 48 voice conversations over a DS-1 medium.


A procedure for modifying a stream of data carried so that it may be carried via a different type of network. For example, transcoding allows H.320 video encoding, carried via circuit switched TDM systems to be converted to H.323 so that it can connect with and be transmitted across packet switched ethernet LAN.


A person who listens to a tape recording and types the words he hears. The word, transcriptionist, derives from the verb to transcribe. The most common employment of transcribers is in the medical industry, where busy doctors talk into tape recorders telling good and bad news of their patients . And even busier transcriptionists type those words into the patient's medical records, or whatever.


A device which converts one form of energy into another. The diaphragm in the telephone receiver and the carbon microphone in the transmitter are transducers . They change variations in sound pressure (your voice) to variations in electricity, and vice versa. Another transducer is the interface between a computer, which produces electron - based signals, and a fiber- optic transmission medium, which handles photon-based signals.


A telephone system feature which provides the ability to move a call from one extension to another. It is probably the most commonly used and misused feature on a PBX. Before you buy a PBX, check out how easy it is to transfer a call. If you have a single line phone, you should simply hit the touch hook, hear a dial tone and then dial the chosen extension number and hang up. This sounds easy in principle, but many people find it difficult since they associate the touch hook with hanging up the phone. Some companies have gotten around this by putting a "hook flash" button on the phone itself. Such a button is like having an autodial button which just makes the exact short tone you make when you quickly hit the hook flash button. An even better solution is an electronic phone with a button specially marked "transfer," or a button next to a screen which lights up "transfer." Failing to efficiently transfer a call is the easiest way to give your customers the wrong impression of your firm. Think of how many times have you called a company only to be told it wasn't the fellow's job and he will transfer the call, but "If we get cut off, please call Joe back on extension 2358." There are typically four types of Transfer: Transfer using Hold, Transfer using Conference, and Transfer with and without Announcement.

Transfer Callback

A phone system feature. After a specified number of rings, an unanswered transferred call will return to the telephone which originally made the transfer.

Transfer Delay

A characteristic of system performance that expresses the time delay in processing information through a data transmission system.

Transfer Impedance

A measure of shield effectiveness.

Transfer Mode

A fundamental element of a communications protocol, transfer mode refers to the functioning arrangement between transmitting and receiving devices across a network. There are two basic transfer modes: connection-oriented and connectionless. Connection-oriented network protocols require that a call be set up before the data transmission begins, and that the call subsequently be torn down. Further, all data are considered to be part of a data stream. Examples of connection-oriented protocols include analog circuit-switched voice and data, ISDN, X.25 and ATM.

Connectionless protocols, on the other hand, do not depend on such a process. Rather, the transmitting device gains access to the transmission medium and begins to transmit data address to the receiver, without setting up a logical connection across the physical network. LANs (e.g. Ethernet and Token Ring) make use of connectionless protocols, as does SMDS, which actually is an extension of the LAN concept across a MAN (Metropolitan Area Network). For more detail, see Connection Oriented and Connectionless Mode Transmission.

Transfer Protocols

Protocols are all of the packaging" that surround actual user data to tell the network devices where to send the data, who it comes from, and how to tell if it arrived. Transfer protocols are designed for the efficient moving of larger chunks of user data.

Transfer Rate

The speed of data transfer ” in bits, bytes or characters per second ” between devices.

Transfer Switch

Usually a switch which reverses two input-output combinations.

Transfer Time

A power backup term. Transfer time can refer to either the speed to which an off-line UPS transfers from utility power to battery power, or to the speed with which an on-line UPS switches from the inverter to utility power in the event of an inverter failure. In either case the time involved must be shorter than the length of time that the computer's switching power supply has enough energy to maintain adequate output voltage. this hold-up time may range from eight to 16 milliseconds , depending on the point in the power supply's recharging cycle that the power outage occurs, and the amount of energy storage capacitance within the power supply. A transfer time of 4ms is most desirable , however, it should be noted that an oversensitive unit may make unnecessary power transfers.


Transformers are devices that change electrical current from one voltage to another. A step-up transformer increases the voltage and a step-down transformer decreases voltage. The power of an electric current must be conserved so just as voltage is increased, current is decreased. Transformers work by feeding an alternating current into a primary coil. The primary coil induces a magnetic field in a secondary coil which is connected to an energy using load. The difference between the number of coils in the primary coil versus the secondary coil determines whether the voltage will be stepped up or down. One reason for using a transformer is that commercial power is typically 120 or 240 volts while many phone systems (and other computer-type "things") work best on 48, 24 or lower voltage.

Transformer Exciting Network

See TEN.

Transhybrid Loss

The transmission loss between opposite ports of a hybrid network, that is between the two ports of the four-wire connection.


Any high-speed, short duration increase or decrease impairment that is superimposed on a circuit. Transients can interrupt or halt data exchange on a network. See HIT.

Transient Mobile Unit

A mobile unit communicating through a foreign base station.


The transistor was invented in 1947 by John Bardeen, Walter H. Brattain and William Shockley of Bell Laboratories. The first transistor comprised a paper clip, two slivers of gold, and a piece of germanium on a crystal plate. Here is an explanation of how a transistor works, taken from "Signals, The Science of Telecommunications" by John Pierce and Michael Noll:

"To understand how a transistor works, we must look at the laws of quantum mechanics. We commonly picture an atom as a positive nucleus surrounded by orbiting electrons ... Vacuum tubes rely on the ability of electrons to travel freely with any energy through a vacuum . Transistors rely on the free travel of electrons through crystalline solids called semiconductors ... Semiconductors (such as silicon or gallium arsenide) differ from pure conductors, such as metals, in how full of electrons are the energy bands that allow free travel." Depending on their design, transistors can act as amplifiers or switches. See Transistor Milestones and Transistor Radio.

Transistor Milestones

Point-contact transistor


Single-crystal Germanium


Grown junction transistor


Alloy junction transistor


Zone melting and refining


Single-crystal Silicon


Diffused-base transistor


Oxide masking


Planar transistor


MOS transistor


Epitaxial transistor


Integrated circuits


Transistor Radio

Sony unveiled the first transistor radio in 1955. See Sony.

Transit Delay

  1. In ISDN, the elapsed time between the moment that the first bit of a unit of data (such as a frame) passes a given point and the moment that bit passes another given point plus the transmission time of that data unit.

  2. As an ATM term, it is the time difference between the instant at which the first bit of a PDU crosses one designated boundary and the instant at which the last bit of the same PDU crosses a second designated boundary.

Transit Exchange

The European equivalent of a tandem exchange.

Transit Timing

A method of eliminating looping between nodes used in the network layer of some packet-switched systems. This method is used in the Internet Protocol (IP) portion of Transmission Control Protocol/Internet Protocol (TCP/IP).

Transition Point

TP. A location in the horizontal cabling subsystem where flat undercarpet cabling connects to round cabling.

Transition Probabilities

Probabilities of moving from one state to another.

Transition Zone

The zone between the far end of the near-field region and the near end of the far-field region. The transition is gradual.


To change the digits dialed on your phone into digits necessary for routing the call across the country. See Translations.

Translating Bridge

A special bridge that interconnects different LAN types using different protocols at the physical and data link layers , such as Ethernet and Token Ring. A translating bridge supports the physical and data link protocols of both LAN types. When they forward packets from one LAN to another, they manipulate the packet envelope to conform to the physical and data link protocols of the destination LAN. For a longer explanation, see Bridge.


The interpretation by a switching system of all or part of a destination code to determine the routing of a call. See Translations.


Here is a definition from Bellcore, who works with the telephone industry: Translations is the changing of information from one form to another. Example: In common control switching systems employing digit storage devices and decoding devices, the dialed digits are stored in a receiver or a tone decoder. The receiver/decoder translates the dialed digits data appropriate for the completion of the call and passes to a processor. With the advent of stored program control, as exemplified in a lA ESS, 5ESS-2000, DMS-100 systems, the translation function has been greatly expanded. When a customer originates a call, for example, the system needs to know if the line is denied outgoing service, if the line is being observed , what the line class is, what special equipment features it has, etc. The line equipment number is given to the translation program as an input. The translation program performs a translation and returns the answers to these questions in a coded form suitable for use by the central processor. The important thing to remember in considering the translation function in the stored program switches is the translation function is employed many times throughout the process of a call and the interplay between the translation programs and other programs is frequent.

Here's my definition: Translations are changes made by the network to dialed telephone numbers to allow the call to progress through the network. Sometimes the translations are made automatically. Take one series of dialed numbers ; convert them to another. Sometimes, translations are done with the help of "look up" tables, also called databases. Here's an example of translations done with the help of a database. TELECONNECT Magazine has a WATS line, 1-800-LIBRARY. If you dial it on the phone, you'll see it is really 1-800-542-7279. But this is not its real number. When someone in California dials 1- 800-LIBRARY, MCI's long distance network recognizes the "1-800" portion of the call and sends it to a special central office somewhere out west. When the call arrives, a computer looks up the number 800-542-7279 in its database and translates that to 1-212-691- 8215 and puts the call back into the network. Within seconds, that number in New York, 212-691-8215 rings.


  1. A communications device that receives signals in one form, normally in analog form at a specific frequency, and retransmits them in a different form.

  2. A device that converts information from one system into equivalent information in another system.

  3. In telephone equipment, it is the device that converts dialed digits into call-routing information.

  4. In computers, it is a program that translates from one language into another language and in particular from one programming language into another programming language.

  5. In FM and TV broadcasting, it's a repeater station that receives a primary station's signal, amplifies it, shifts it in frequency, and rebroadcasts it.


To convert the characters of one alphabet to the corresponding characters of another alphabet.


Sending electrical signals carrying information over a line to a destination. Bellcore says that transmission has the following definitions:

  1. Designates a field work, such as equipment development, system design, planning, or engineering, in which electrical communication technology is used to create systems to carry information over a distance.

  2. Refers to the process of sending information from one point to another.

  3. Used with a modifier to describe the quality of a telephone connection: good, fair, or poor transmission.

  4. refers to the transfer characteristic of a channel or network in general or, more specifically, to the amplitude transfer characteristic. You may sometimes hear the phrase, "transmission as a function of frequency."

Transmission Block

A group of bits or characters transmitted as a unit, with an encoding procedure for error control purposes.

Transmission Channel

All of the transmission facilities between the input (to the channel) from an initiating node and the output (from the channel) to a terminating node. In telephony, transmission channels may be of various bandwidths: e.g. nominal 3- kHz, nominal 4-kHz, or nominal 48-kHz (group). "Transmission channel" should not be confused with the more general term "channel."

Transmission Code

A code by which information is sent and received on a transmission system.

Transmission Coefficient

The ratio of the transmitted field strength to the incident field strength when an electromagnetic wave is incident upon an interface surface between media with two different refractive indices. In a transmission line, the ratio of the complex amplitude of the transmitted wave to that of the incident wave at a discontinuity in the line. A number indicating the probable performance of a portion of a transmission circuit. The value of a transmission coefficient is inversely related to the quality of the link or circuit.

Transmission Control

Category of control characters intended to control or help transmission of information over telecommunication networks. See TCP.

Transmission Control Characters

A group of characters used to facilitate or control data transmission. Examples are NAK (Not acknowledge ) and EOT (end of transmission).

Transmission Control Protocol

TCP. A specification for software that bundles outgoing data into packets (and bundles incoming data), manages the transmission of packets on a network, and checks for errors. TCP is the portion of the TCP/IP protocol suite that governs the exchange of sequential data. In more technical terms, Transmission Control Protocol is ARPAnet-developed transport layer protocol. Corresponds to OSI layer 4, the transport layer. TCP is a connection-oriented, end-to-end protocol. It provides reliable, sequenced , and unduplicated delivery of bytes to a remote or local user. TCP provides reliable byte stream communication between pairs of processes in hosts attached to interconnected networks. It is the portion of the TCP/IP protocol suite that governs the exchange of sequential data. See TCP/IP for a much longer explanation.

Transmission Convergence

TC. Transmission Convergence Sublayer, a dimension of the ATM Physical Layer (PHY). See TC.

Transmission Electronics

Any of the various devices used in conjunction with different transmission media to convert from one transmission method to another.

Transmission electronics devices typically include multiplexing equipment and Asynchronous Data Units.

Transmission Facility

A piece of a telecommunications system through which information is transmitted, for example, a multi pair cable, a fiber optic cable, a coaxial cable, or a microwave radio.

Transmission Frame

A data structure, beginning and ending with delimiters, that consists of fields predetermined by a protocol for the transmission of user and control data.

Transmission Level

The power of a transmission signal at a specific point on a transmission facility. See Decibel.

Transmission Level Point

TLP. A designated physical point on a circuit where the transmission level, or amplitude, is measured. Referencing this point in relation to others in the network can determine the performance of the network. See also Level, Loss, and Pad.

Transmission Limit

The wavelengths above and below which the fiber ceases to be transparent and therefore, can no longer transmit information.

Transmission Line

A coaxial cable or waveguide used for connecting a transmitter to an antenna.

Transmission Loss

Total loss encountered in transmission through a system.

Transmission Media

Anything, such as wire, coaxial cable, fiber optics, air or vacuum, that is used to carry an electrical signal which has information. Transmission media usually refers to the various types of wire and optical fiber cable used for transmitting voice or data signals. Typically, wire cable includes twisted pair, coaxial, and twinaxial. Optical fiber cable includes single, dual, quad, stranded, and ribbon.

Transmission Objectives

A stated set of desired performance characteristics for a transmission system. Characteristics for which objectives are stated include loss, noise, echo, crosstalk, frequency shift, attenuation distortion, envelope delay distortion, etc.

Transmission Pattern

See Radiation Pattern.

Transmission Payload

The interface bit rate minus the overhead bits.

Transmission Protocol O (TPO)

OSI (Open Systems Interconnection) Transmission Protocol Class O (Simple Class). This is the simplest OSI Transmission Protocol, useful only on top of an X.25 network (or other network that does not lose or damage data).

Transmission Protocol 4 (tp4)

OSI (Open Systems Interconnections) Transmission Protocol Class 4 (error detection and recover class). This is the most powerful OSI Transmission Protocol, useful on top any type of network. TP4 is the OSI equivalent to TCP (Transmission Control Protocol).

Transmission Security Key

TSK. A key that is used in the control of transmission security processes such as frequency hopping and spread spectrum.

Transmission Speed

Number of pulses or bits transmitted in a given period of time, expressed variably in Bits Per Second (BPS), Words Per Minute (WPM), Characters Per Second (CPS), an occasionally as Lines Per Minute (LPM) in printer transmission. Skilled technologists can translate one to the other.


The way many LCD (liquid crystal display) screens on laptops reflect light.

Transmit Bus

In AT&T's Information Systems Network (ISN), the circuit on the backplane of the packet controller that transports message packets from sending device interface modules to the switch module.

Transmit Digital Intertie

TDI. A 16-channel serial converter which converts the TDM Data Bus from parallel format to serial format for transmission between nodes.


The ratio of transmitted power to incident power. In optics, frequently expressed as optical density or percent; in communications applications, generally expressed in decibels.


The device in the telephone handset which converts speech into electrical impulses for transmission.

Transmitter Distributor

A device in a teletypewriter system which converts the information from the parallel form in which it is used in the keyboard-printer to and from the serial form which it is transmitted on the transmission line.

Transmitter Start Code

A coded control character or code sequence transmitted to a remote terminal instructing that terminal to begin sending information.


The transmobile (not to be confused with a TRANSPORTABLE) is another type of cellular phone. It is essentially a standard 3-watt mobile unit ” without an external battery pack ” that can be quickly and easily moved from one vehicle to another. It draws its power from the vehicle's battery via a cigarette lighter plug. See Bag Phone.


A device that takes a bunch of voice analog phone conversations and converts them directly into a T-1 1.544 megabit per second bit stream ” without the need for de-multiplexing the bunches down to individual conversations, then digitizing them, then bundling them up into a T-1 digital bit stream. A transmultiplexer does it all in one go.


  1. A data communications mode that allows equipment to send and receive bit patterns of virtually any form. The user is unaware that he is transmitting to a machine that receives faster or slower, or transmits to him faster or slower, or in a different bit pattern. All the translations are done somewhere in the network. He is unaware of the changes occurring ” they are transparent. ISDN is planned to be transparent.


"Transparent Communications"

  1. A basic objective of telecommunications systems, to make the transportation of information invisible to the user.

  2. In data communications, a suspension of control character recognition in certain systems while information transfer is in progress.


An imaging term. A setting available in many image- processing functions that allows part of the underlying image to show through. 80 percent opacity is equivalent to 20 percent transparency.


Fine or sheer enough to be seen through. Something that is transparent exists for some reason, but is invisible, or nearly so. In other words, it does not impair or affect the users' operation of the system or feature. In fact, the user need not interact with the transparent feature, and generally is totally unaware that it exists. Think of a pane of glass that serves to protect the interior of a building and its occupants from the elements, but does not affect the users' ability to see through it.

When applied to telephone communications, the term is used to characterize the provision of a feature or service such as Automatic Route Selection in a such a way that the user is unaware of it and it has no affect on the way he uses the telephone. It's "trans- parent" to him. Translations, for example, are transparent to the telephone user. Similarly, protocol conversions are transparent. See also Translations, Transparency, and Virtual.

Transparent Bridging

Transparent bridging is so called because the intelligence necessary to make relaying decisions exists in the bridge itself and is thus "trans- parent" to the communicating workstations. It involves frame forwarding, learning workstation addresses and ensuring no topology loops exist.

Transparent GIF

Transparent GIFs are useful because they appear to blend in smoothly with the user's display, even if the user has set a background color that differs from that the developer expected. They do this by assigning one color to be transparent ” if the Web browser supports transparency, that color will be replaced by the browser's background color, whatever it may be.

Transparent Image

An image that has had one color, usually the background, designated as 'transparent,' so that when the image is displayed in a browser, the image's background is colored with the browser's background color. The effect is an image that does not have a visible rectangular background.

Transparent Mode

  1. The operation of a digital transmission facility during which the user has complete and free use of the available bandwidth and is unaware of any intermediate processing. Generally implies out-of-brand signaling (also called Clear Channel).

  2. In BSC data transmission, the suppression of recognition of control characters, to allow transmission of raw binary data without fear of misinterpretation.

  3. An operational mode supported by the T3POS PAD which enables the use of existing credit authorization and data capture link level protocols. This mode requires minimal modifications to the POS (Point Of Sale) terminal, and no modification to the ISP/Credit Card Association (CCA) host system software.

Transparent Networking Transport

TNT. A service for transporting of LAN data across WANs in which all responsibility for the WAN transport is assumed by the WAN and is therefore invisible to the LAN.

Transparent Routing

A method used by a bridge for moving data between two networks. With this type of routing, the bridge learns which computers are operating on which network. It then uses this information to route packets between networks. It does not rely on the sending computers for its decision-making routine. A special kind of bridge combines the practice of transparent routing with source routing. It is called a source routing transparent (SRT) bridge. It examines each packet that comes by to see if it is using IBM's special source routing protocol. If so, this protocol is used to forward the packet. If not, the transparent method is used. Thus, the SRT bridge will support both IBM and non- IBM network protocols. See also Bridge and SRT. Compare with Source Routing.


  1. A transponder is a fancy name for radio relay equipment on board a communications satellite. Just like its domestic microwave counterpart (which you see along highways), a transponder will receive a signal, amplify it, change its frequency and then send it back to earth. On a satellite transponder that uses frequency modulation, the bandwdith required for an analog tv signal is 27Mhz. Since satellites are power limited, FM is the analog modulation of choice. In exchange for wide bandwidth and poor spectral efficiency, FM offers improved signal-to-noise ratio. On a terrestrial TV station or cable TV network where power is not an issue, amplitude modulation is used which offers better spectral efficency so the bandwidth neeeded for an analog TV signal is only 6Mhz.

  2. A transponder on an airline is a slightly different kettle of fish. When a radar signal strikes a airline, it activates an electronic transmitter called a transponder. The transponder sends out a coded signal to the ground radar. The code appears next to the radar image of the plane, allowing the controller to identify each plane under his control. Newer aircraft have automatic collision avoidance systems that will change the flight path of two or more planes if they appear to the systems as though they're going to crash.

Transport Driver

A network device driver that implements a protocol for communicating between Lan Manager and one or more media access control drivers. The transport driver transfers Lan Manager events between computers on the local area network.

Transport Efficiency

An AT&T term for the ability to carry information through a network using no more resources than necessary. Transport efficiency is achieved, for example, by statistical transport, which removes silent intervals from voice, data or other traffic and carries only the bursts of meaningful user information.

Transport Layer

Layer 4 in the Open Systems Interconnection (OSI) data communications reference model that, along with the underlying network, data link and physical layers, is responsible for the end-to-end control of transmitted information and the optimized use of network resources. Layer 4 defines the protocols governing message structure and portions of the network's error-checking capabilities. Also serves the session layer. Software in the transport layer checks the integrity of and formats the data carried by the physical layer (layer 1, the network wiring and interface hardware), managed by the data link layer (layer 2) and possibly routed by the network layer (layer 1, which has the rules determining the path to be taken by data flowing through a network). See OSI.

Transport Level

Level 4 of the Open System Interconnection (OSI) model. The Transport level allows end users to communicate oblivious to network constraints imposed by the lower levels. Passes data from the Session level on to the Network Level and ensures that the data reaches the other end. Level 4 also provides for flow management.

Transport Medium

The actual medium over which transmission takes place. Transport media include copper wire, fiber optics, microwave and satellites.

Transport Overhead

1.728 MB/s of bandwidth allocated within each SONET STS-1 channel to carry alarm indications , status information, and message signaling channels for the preventive and reactive maintenance of SONET transmission (Transport) links.

Transport Protocol

A protocol that provides end-to-end data integrity and service quality on a network. Windows 95 Resource Kit defines transport protocol as how data should be presented to the next receiving layer in the networking model and packages the data accordingly . It passes data to the network adapter driver through the NDIS interface. See also Transport Protocol Class Four.

Transport Protocol Class Four

TP4. An International Standards Organization (ISO) transport layer protocol designated as ISO IS 8073 Class Four Service. TP4 has been adopted by the U.S. Department of Defense and specified in the U.S. Government OSI Profile (GOSIP).

Transportable Cellular Phone

The transportable cellular phone is a standard 3-watt mobile phone that can be removed from the car and used by itself with an attached battery pack. The entire unit is generally mounted or built into a custom carrying case to make it easy to carry on your shoulder. Although technically "portable," the transportable should not be confused with the true portable one-piece cellular phone. Also known as a "bag phone" or "briefcase phone"; refers to a cellular handset that is packaged with a larger carrying case containing a full-scale power supply.

Transposed pair

A wiring error in a twisted-pair cabling where a twisted pair is connected to a completely different set of pins at both ends (instead of pin 1 to pin 1, and pin 2 to pin 2, the cable is incorrectly wired pin 1 to pin 8, and pin 2 to pin 7, for example).


Interchanging the relative position of conductors at regular intervals to reduce crosstalk. In data transmission, a transmission defect in which, during one character period, one or more signal elements are changed from one significant condition to the other, and an equal number of elements are changed in the opposite sense.

Transverse Interferometry

The method used to measure the index profile of an optical fiber by placing it in an interferometer and illuminating the fiber transversely to its axis. Generally, a computer is required to interpret the interference pattern.

Transverse Parity Check

Type of parity error checking performed on a group of bits in a transverse direction for each frame. See Parity Check.

Transverse Scattering

The method for measuring the index profile of an optical fiber or preform by illuminating the fiber or preform coherently and transversely to its axis, and examining the farfield irradiance pattern. A computer is required to interpret the pattern of the scattered light.


  1. See Trap and Trace.

  2. A programming term. A programmer sets a trap for something to happen when something else happens. You might say "Wait for the mouse to come by, when it does, close the trap." A trap might be sprung when a phone rings or when someone hangs up. In network management, a trap is a mechanism permitting a device to automatically send an alarm for certain network events to a management station. Typically, network management information is gained by polling network nodes on a regular basis. This strategy can be modified when a trap is set from a network node. With traps, a node alerts the management station of a catastrophic problem. The management station can then immediately initiate a polling sequence to the node to determine the cause of the problem. This strategy is often called trap-directed polling.

  3. A video term. A circuit often called a filter, which is used to attenuate undesired signals while not affecting desired signals. Typically a signal channel trap to remove a single premium service which the subscriber is not paying for. See Notch Filter, Positive Trapping, and Negative Trapping.

  4. TRansmission Alarm Processor

Trap And Trace

A telephone company term. Trap and Trace is the term for equipment and procedures for determining the source of an incoming call (typically a harassing call). The phone company uses traps to trace the source of the incoming call. There are two types of traps ” the Terminating Trap and the Originating Trap. A terminating trap sits on the receiving phone line. In the old days, a terminating trap was a physical piece of equipment. These days, with electronic central offices, it's basically a command to the computer running the central office to keep track of all information about the source of all incoming calls. That information might be the originating telephone number. It might be the trunk number on which the call came in on. Such trunk number might look like TGN701. Or it might be the CLLI code ” which stands for the Common Language Location Identifier. The CLLI code (pronounced "silly") consists of 11 characters. A sample CLLI code is "nycmny18dso." That says the call is coming in from New York City, Manhattan from a central office called 18DSO (which I happen to know is an AT&T 5E central office located on West 18th Street). Once the terminating trap identifies the possible direction /source / incoming trunk of the offending phone calls, the phone company will work it back towards the originating line. It will attach an Originating Trap to the offending trunk, then to the offending tandem office, then to the local central office. This can be a tedious and time consuming business. With the advent of Caller ID ” both local and nationwide ” trapping and tracing is getting faster and easier. Now if you receive an harassing call, you simply hit *57 the moment the call is over (GTE uses *69). This "tags" the incoming call's number and other information in your central office's records. You, as subscriber, can't get access to that information. But a law enforcement agency (i.e. one investigating your annoying calls) can. See Annoyance Call Bureau and Wire Tap.

Trap Door

Hidden software or hardware mechanism that, when triggered, allows system-protection mechanisms to be circumvented.


Pejorative term for the TRS-80 (Tandy Radio Shack-80), an early PC sold by the Tandy Corporation through its Radio Shack retail stores. See TRS-80.


Also referred to as dumpster diving, a term used by hackers for going through trash in an effort to get information that will facilitate breaking into computers. People often write passwords on paper, then put the paper in the trash. Be careful.


Software that is so poorly designed that it winds up in the garbage can.


Transcoder and Rate Adapter Unit. A transmission function of the BSS that converts speech from the user of a mobile station into digital representation needed for an ISDN, wireless network.

Travel Card

Another name for a telephone credit calling card. Travel card calls that are placed against a travel card number issued by the service provider, typically a phone company. As each call is completed, the long distance switch increases that card's account balance by the amount of each call. During the processing of a call, if the travel card is invalid or if the caller does not respond to a system prompt, the serving switch will typically ask the caller to hold the line for a live operator, and transfers the call to an Operator Workstation. When the operator answers, the OWS screen shows call information, including card number (if already entered), destination number (if already entered), trunk identification, and a failure code.

Traveling Class Mark

TCM. A code that accompanies a long distance call. When Automatic Route Selection (ARS) or Uniform Numbering/Automatic Alternate Routing (UN/AAR) selects a tie trunk to a distant tandem PBX, the traveling class mark (TCM) is sent over the tie trunk. It is then used by the distant system to determine the best available long distance line consistent with the user's calling privileges. The TCM indicates the restriction level to be used based on the phone, trunk or attendant originating the call or the authorization code, if dialed.


See Rack.


Transit Routing Control Table.


Trouble Reporting Central Office.


A billing and collections term. The specific steps of the collection process to which an account is subject. The treatment level may begin with a "courtesy" call which may go something like "Mr. Newton, this is Mrs. Horak with your friendly telephone company. We've noticed that your account is past due. In fact, you have not paid your telephone bill for three months. When might we expect payment?" At this point, Mrs. Horak verifies employment, which is a standard step. Now the conversation takes a turn for the worse. "Mr. Newton, do I understand correctly that you no longer work for Flatiron Publishing, and that you expect me to believe that you now work for Harry Newton Enterprises? Really Mr. Newton! I must request immediate payment by cash, cashier's check or money order! Failure to comply with this demand by the end of the business day will result in the disconnection of your service. Oh, did I mention that we will require a security deposit of $5,000? That, too, will have to be paid by the end of the business day. Yes, Mr. Newton, I am fully aware that it is 4:59PM. Mr. Newton, Mr. Newton." (Aside: "Ray, those guys in the switchroom are really good! They cut Harry's service off at exactly 5:00. That'll teach him to pay his bills on time!") Note: This scenario actually is very inaccurate- the guys in the switchroom aren't nearly that good. Actually, treatment levels are highly sensitive to the size of the bill, the age of the receivable, the history of the account, and other factors. Treatment levels may begin with a courtesy call, progress through several calls of a firmer tone, a formal letter or two of successively firmer tone, suspension of service, and disconnection. Restoral of service and reconnection entail service fees and generally involve a security deposit. If you don't pay your final bill quickly, you'll be dealing with a collection agency. Pay your telephone bill on time.

Treatment Level

Treatment level is a term used in some telephone companies' billing and collections processes. The phrase is used to help a telephone company identify where a particular customer is in the collections/overdue billing process and proper protocol in treating the customer. See Treatment.

Treaty of Breda

See Nutmeg.


  1. A network topology shaped like a branching tree. (What else?) It is characterized by the existence of only one route between any two network nodes. Most CATV distribution networks are tree networks.

  2. In MS-DOS, a tree describes the organization of directories, subdirectories, and files on a disk.

Tree Hugger

IBM-speak for an employee who resists a move or any other change.

Tree Mailbox

A special function mailbox that provides the caller with a menu and allows selections from the menu using single digit commands.

Tree Network

A network configuration in which there is only one path between any two nodes.

Tree Search

In a tree structure, a search in which it is possible to decide, at each step, which part of the tree may be rejected without further search.

Tree Stand

Aerial Cross Box. A cross box on a pole. Used where vandals live or when there's a narrow easement.

Tree Structure

Describes the organization of directories, subdirectories, and files on a disk.

Tree Topology

A network cabling architecture in which nodes are connected by cables to a central, or trunk, cable with a central retransmission capability.


Slang for documentation or other printed material.

Trellis Code

See Trellis Coding.

Trellis Coding

A method of forward error correction used in certain high-speed modems where each signal element is assigned a coded binary value representing that element's phase and amplitude. It allows the receiving modem to determine, based on the value of the preceding signal, whether or not a given signal element is received in error. See V.32 and V.32 bis. In QPAM, trellis coding adds extra bits (the trellis code) to data transmitted over a modem. The extra bits are fed to a mathematical algorithm at the receiver that lowers the number of possible choices in a QPAM eye-pattern. Helps modems do "on the fly" error detection and correction. See QPAM.

Trellis Coding Modulation

TCM. A modem modulation technique in which sophisticated mathematics are used to predict the best fit between the incoming signal and a large set of possible combinations of amplitude and phase changes. TCM provides for transmission speeds of 14,400 bps and above on single voice grade phone lines. See V.32 and V.32 bis.

Tremendously High Frequency

Frequencies from 300 GHz to 3000 GHz.


Transmission Expert.




Technical Review Group.


On August 30, 1995, MCI Communications announced the deployment of a technology that will enable it to increase the capacity of its network by 50 percent without any additional fiber optic lines. The technology, known as Tri-Color Wave Division Multiplexing (Tri-CWDM), allows existing fiber to accommodate three light signals instead of two, by routing them at different light wavelengths, through the combined use of narrow and wide band wave division multiplexing. With this method, lightwaves are transmitted at 1557 nanometers (nm) and 1553 nm to a wide band WDM device, where a 1310 nm signal is added. Once combined, the three signals are routed through a single fiber to the next site where they are separated and sent to the receivers. Transmitting three signals in each direction allows for three different transmit pairs on just two fibers, effectively increasing the total network capacity from 5 gigabits to 7.5 gigabits. MCI officials say the technology will be particularly valuable in major metropolitan areas, where the company is enjoying outstanding growth in voice and data traffic. Essentially TRI-CWDM is now obsolete, replaced by Dense Wave Division Division Multiplexing. See DWDM.


Tri-Mode describes a cell phone that operates in North America on both digital bands ” 800 Mhz and 1900 Mhz ” along with analog AMPS in the 800 Mhz band. The reason you'd want such a phone is simple: Digital service is often cheaper better in areas you can get it. But you can't get it everywhere. If you travel you need a cell phone you can use everywhere. Thus the idea of carrying a three band cell phone and subscribing to a service that gets you access to all three. Tri-mode can also apply to other parts of the world but I am not familiar with the different band/mode interactions. The U.S. doesn't have a specific wireless carrier that provides all three modes but Canada does. Commonly, wireless carriers have agreements that allow handsets to receive a competitor's service when roaming or if the primary service contains areas of poor service which would otherwise cause dropped calls. So a carrier may provide only 1900 Mhz PCS but when necessary allow the phone to operate in 800 Mhz AMPS, offered by another carrier, so that calls are not dropped. This concept applies to the Dual Band phones, as well. See Dual Band.


A method of locating the source of a radio signal through the use of three receivers, each of which focuses on the direction of maximum signal strength. Through the use of three receivers, it easily is possible to plot the general location of the transmitter, even though radio signals bounce off and are absorbed by physical obstructions such as buildings , trees and cars . This process, also known as Angle of Arrival, now can be accomplished by two, or even a single, receivers employing much more sophisticated, smart-antenna technology.

Triaxial Cable

A cable construction having three coincident axes, such as a conductor, first shield and second shield all insulated from one another.

Tribit Transmission

A transmission technique used by some modems in which three bits are transmitted simultaneously .


The lower rate signal input to a multiplexer for combination (multiplexing) with other low rate signals to form an aggregate higher rate signal.

Tributary Circuit

A circuit connecting an individual phone to a switching center.

Tributary Office

A local office, located outside the exchange in which a toll center is located, that has a different rate center from its toll center.

Tributary PBX

An exchange within the main PBX configuration but with its own listed number. The only difference between a satellite and a tributary PBX is that the tributary PBX has a direct incoming connection from the public network. See Satellite PBX.

Tributary Station

In a data network, a station other than the control station. On a multi point connection or a point-to-point connection using basic mode link control, any data station other than the control station.

Tributary Unit

The SDH equivalent of a Virtual Channel in SONET terminology. A Tributary Unit might comprise a voice channel within a Virtual Tributary, which might take the form of a T-1 frame.


The technical name for RGB representation of color to create all the colors in the spectrum.


The name of a BITNET mail server package which provides access to anonymous FTP archive sites via e-mail.

Trickle Charge

The continuous charging of an electrical battery. It keeps the batteries continuously charged, which is a good thing. That way, the phones still work when the lights go out ” at least until the batteries run down.

Tickle Down Economics

Economists believe that if the government reduces taxes, people with more moneyso

See also Tirckle Down Ergonomics.

Trickle Down Ergonomics

The practice of stealing (or being given) an Herman Miller Aeron chair , desk, computer, a monitor, or other tools of the trade after you've been laid off. See Trickle Down Economics.


An application-specific process invoked by a database management system as a result of a request to add, change, delete, or retrieve a data element. For example, Local Number Portability (LNP) currently typically involves the use of two telephone numbers when a customer ports from one carrier to another. If a caller dials the old telephone number, the Central Office (CO) of the previous carrier recognizes that the old number is no longer active. That old 10-digit number triggers the CO to consult the SCP (Signaling Control Point) of the supporting AIN (Advanced Intelligent Network). The SCP dips into a database, extracts the new 10-digit telephone number and the CIC (Carrier Identification Code) of the CLEC (Competitive Local Exchange Carrier) to which the service has been ported, and provides the CO with that information, in order that the call can be handed off to the new carrier and eventually terminated . See also AIN, Basic Call State Model, CIC, CLEC, LNP, and SCP.


The process of detecting a word (or utterance) and capturing the speech data associated with that word (or utterance) for subsequent processing. See also Trigger.


Uncompiled code residing on an intelligent database server. See also Trigger.


A low to modestly priced item. Typically these are T-shirts, hats, cups and pens used for promotional or motivational purposes. Also used to bribe and cajole software developers into working even more excessive hours. When the telex business was in full bloom, trinkets were used to motivate telex operators into preferring one supplier over another. Trinkets were necessary because the price for service and equipment was identical, since it was heavily regulated.

Trinkets and Trash

A new term for trinkets. See Trinkets.


A combination of a heated cathode , a relatively cold anode, and a third electrode for controlling the current flowing between the other two; the whole enclosed in an evacuated bulb. Variously called, audion, pliotron, radiotron, oscillion, audiotron, aerotron, electron tube, vacuum tube, etc.


Telephony Routing over IP protocol. TRIP was engineered by a working group of the IETF as a tool for inter-domain exchange of telephone routing information. It can also be used as a means for gateways and soft switches to export their routing information to a Location Server (LS), which may be co-resident with a proxy or gatekeeper. This LS can then manage those gateway resources. TRIP will give VoIP (Voice over Internet Protocol) providers the ability to dynamically exchange routing and line propagation information between one another helping to create the global Public Internet Telephone Network.

Triple DES

A security enhancement of single-DES encryption that employs three successive single-DES block operations. Different versions use either two or three unique DES keys. This enhancement is considered to increase resistance to known cryptographic attacks by increasing resistance to known cryptographic attacks by increasing the effective key length.

Triple Mode

A combined analog and digital mobile phone. Allows operation of the phone in the existing analog system frequency (800 MHz) and in both digital frequencies (800 MHz and 1900 MHz).

Triple Witching

Third Friday in the last month of the quarter. Those months are March, June, September, and December. Equity Options, index options and options on futures (i.e. futures contracts) all expire simultaneously. also the day the that options on futures expire. Historically called triple witching. More volatility. Everyone expired at Friday's close. Triple witching volatility has gone. Now lower ” Some expire at the open . Some expire at the close. Users roll out their beforehand.


A three-legged mounting system used for mounting antenna masts to different structures, including ridged roofs and flat roofs.


The word "trivia" is Latin, meaning three (tri) way (via). The term historically was used to describe a three-way crossroads , or intersection. According to etymologists (i.e., those who study the origins of linguistic forms), it was at such intersections that people, in days gone by, often stopped to exchange in small talk about unimportant matters. These unimportant matters eventually became known as trivia. See also Arcane, Draconian, and Eccentricity.

Trivial File Transfer Protocol

TFTP. A UNIX-based file protocol. TFTP is a simplification of the earlier Simple File Transfer Protocol (SFTP).


Transistor Resistor Logic.


Temporary Restraining Order.

Trojan Horse

A Trojan Horse is a piece of software that appears to do something useful, but which actually performs hidden, usually damaging, action on your computer. For example, a Trojan Horse might be a game program which plays a neat game but at the same time deliberately erases files on your computer. Such software might be distributed by being posted on a web site or it may be sent via e-mail, claiming that it is a product upgrade from a software vendor ” like Microsoft (which never sends out software updates by email). A Trojan Horse is dangerous software. The simple rule is never use software from someone you don't know and haven't verified isn't real. See also Trojan Horse Attack. Malicious Trojan Horse software has evolved to a point where it may sit silently on your computer until some command from the outside (it assumes you're connected to the Internet full-time ) tells your computer to do something, e.g. allow a distant pornographer to make their identity and location by using your computer as a relay station. You, of course, have no idea that you're being used to send pornography or spam.

Trojan Horse attack

A network security term. An attack carried out via software that purports to be useful and benign , but which actually performs some destructive purpose (like erasing all the files on your hard disk) when run. See also Trojan Horse.


  1. A condition when a call comes in a trunk and is transferred back out on a trunk over the same physical path on which it arrived. Suppose a call is placed from location A through the telephone network and arrives at location B. If the call is forwarded to location C, the call turns on itself and returns to the telephone network on its way to location C. The call is said to be "tromboned". The name derives from the suggestion of the curve in the picture similar to the U-shaped slide on a trombone musical instrument. The trombone condition results in two trunks being tied up when the optimal connection would use no trunks at location B. The cure for the tromboning condition is "anti-trom- boning". In the situation described by the figure, the edge telephony switch at location B detects that transferring the call to location C will result in a tromboned trunk, and signals the transfer to the telephony switch in the telephone network to transfer the call. The call will then be set up over a more optimal path, and the trunk at location B will be released. There are at least two common signaling methods for anti-tromboning 1) Centrex flash hook and 2) QSIG path replacement. Tromboning sometimes is known as hairpinning. See also Hairpinning, Path Replacement, and QSIG.

  2. A form of regulatory arbitrage used in telecommunications, and particularly in the cellular world, tromboning is used by some carriers to increase revenues or decrease costs. Tromboning involves a call from country A to country B first going through an international gateway in country C. The termination costs for traffic from C to B may be much less than from A to B. Stupid regulations developed by stupid regulators cause carriers to have to jump through such hoops. The term "tromboning" comes from the unique U-shaped section of the slide trombone. As the slide is pushed out and back in, it creates the tones between the fundamentals and the harmonics. See also Arbitrage and Broker.


Tropscattering is a way of transmitting telecommunications signals between two places by bouncing multiple beams off the atmosphere. See Trospheric Scatter, which is its real name.


The lower layers of the earth's atmosphere. You can bounce certain frequency radio signals off it and use it as an elementary transmission reflector. The troposphere is the region where clouds form, convection is active, and mixing is continuous and more or less complete. The lower layers of the Earth's atmosphere, between the surface and the stratosphere, in which about 80 percent of the total mass of air is located and in which temperature normally decreases with altitude. The thickness of the troposphere varies with season and latitude; it is usually 16 km to 18km over topical regions and 10 km or less over the poles. See Tropospheric Scater and Tropospheric Wave.

Tropospheric Scatter

The propagation of radio waves by scattering as a result of irregularities or discontinuities in the physical properties of the troposphere. The propagation of electromagnetic waves by scattering as a result of irregularities or discontinuities in the physical properties of the troposphere. A method of transhorizon communications using frequencies from approximately 350 MHz to approximately 8400 MHz. The propagation mechanism is still not fully understood , though it includes several distinguishable but changeable mechanisms such as propagation by means of random reflections and scattering from irregularities in the dielectric gradient density of the troposphere, smooth-Earth diffraction, and diffraction over isolated obstacles ( knife -edge diffraction ).

Tropospheric Wave

A radio wave that is propagated by reflection from a place of abrupt change in the dielectric constant or its gradient in the troposphere. In some cases, the ground wave may be so altered that new components appear to arise from reflection in regions of rapidly changing dielectric constant. When these components are distinguishable from the other components, they are called "tropospheric waves."

Trouble Number Display

The operator will know what the trouble is with the phone system by seeing a number pop up on her/his console. That number may pop up automatically or the operator may have to hit the ALM (for ALARM) or similar button.

Trouble Reporting Central Office

TRCO. Office where circuit troubles from OCCs are reported for repair and restoral.

Trouble Ticket

Form used to report problems. Often incorrectly filled-in. Check.

Trouble Ticket Modify

TTMOD. A Verizon definition. The transaction a CLEC or Reseller uses to add, change or delete a previously created Verizon trouble ticket (for example, for rescheduling repair activities). A CLEC or Reseller may submit a modification for any open trouble ticket, but not for a closed trouble ticket.

Trouble Unit

A weighting figure applied to telephone circuit or circuits to indicate expected performance in a given period.

Troubles Per Hundred

Troubles per hundred is a criterion for acceptable customer service which telephone companies and public utility commissions have agreed upon. It's measured in terms of the number of complaints received per hundred telephones in one month. Six complaints per hundred is considered the maximum for acceptable service. See Quality of Service.


A pound of feathers weighs more than a pound of gold. Feathers are weighed by "avoirdupois" weight measure, which has 16 ounces to a pound, while gold is weighed in "troy" measure, which only has 12 ounces to a pound . Just in case you're interested, "avoirdupois" is from Middle English usage of the Old French "avoir de pois," which means "goods of weight," as it originated in commerce. "Troy" also is from Middle English usage, referring to Troyes, France. "Troy" is based on an ounce of 20 pennyweights, or 480 grains, as it originated in finance.


RPOA Conversion Table.


  1. Report Steering Table.

  2. Telecommunication Relay Service. TRS is a service for the hard of hearing. See Telecommunication Relay Service.

  3. Trunked Radio System.


Tandy Radio Shack-80. One of the early PCs. It was introduced by Tandy Corporation through its Radio Shack stores. It was based on the Zilog Z80 chip and began selling in the late 1970s. Along with Apple and Commodore it proved the viability of personal computers. The TRS-80 helped ensure the success of later generations of PCs by introducing a spreadsheet called Visicalc, word processing such as Electric Pencil, WordStar and databases such as dBASE. It also was one of Microsoft's earliest customers for their Basic language package. There were several TRS-80 models including the original Model 1, Model 2, Xenix (UNIX), Model 3 with integrated drives and Model 4. Some of the models could run CP/M or TRSDOS. Tandy later also introduced the Model 100 which was, arguably the first Laptop/Notebook, and for which Bill Gates is alleged to have written much of the software code. Detractors of the TRS-80 referred to it as the "Trash-80." The TRS-80 Model 2 actually had a cage designed for the specific purpose of accepting printed circuit cards. Sadly, Radio Shack never released the technical specs on the cage. No one (including Radio Shack itself) produced cards and the machine was quickly superseded by the IBM PC. In short, Radio Shack once had the market for PCs right at its fingertips. But it blew an incredible opportunity. Sad.


Inside a telephone system, the TRU (the Tone Receiver Unit) is used to retrieve and interpret touch-tone data received. Those tones might be sent by a TSU ” Tone Sender Unit.

Truck Roll

Phone company terminology for physically sending a technician in a service truck into the field to diagnose a problem. Phone companies strive to reduce their truck rolls as there is a real cost involved with maintaining trucks , technicians, handheld test equipment, etc. Phone companies are setting so more and more of their installations can be done by their customers. See Splitter.

True North

North based upon the earth's axis, which points to the star Polaris.


A "true-up" essentially is a reconciliation of actual experience against plans. For example, one might take out a software license, the cost of which is sensitive to the number of "seats" (i.e., clients , or desktop computers) running the software against one or more servers, or to the number of simultaneous users, or even to the number of times or total length of time that the software is actually used. The server may keep track of that usage. At some point, the contract may call for a true-up, at which point the actual usage is compared to the contract terms. Any additional usage costs are then due and payable. Similarly, a utility may be granted a tariff involving certain rates that are based on certain cost assumptions. At some point in time, a true-up takes place, at which point the actual costs are compared with those on which the rates are based. If the costs are higher, the rates may go up. If the costs are lower, the rates may go down.


TrueSpeech is a low-bandwidth method of digitizing speech, which was created by a company called DSP Group, Inc. Santa Clara, CA. TrueSpeech uses compression to drop one minute of voice down to 62 kilobytes with remarkably little degradation. It is used in many digital telephone answering devices for storing and reproducing voice. TrueSpeech's compression is not meant for high fidelity music. But it is more than acceptable for such business applications as voice mail, voice annotation, dictation, and education and training. The small file size means that it can be transferred more easily to other users by using either a corporate network. The DSP Group describe TrueSpeech an enabling technology for speech compression in personal computers and future personal communications devices. Speech compression is key technology to the effective convergence of personal computers and telephony. TrueSpeech compression is a technology based on complex mathematical algorithms which are derived from the way airflow from our lungs is shaped by the throat, mouth, and tongue when we speak. This shaping is what our ear finally hears. TrueSpeech is 5 to 15 times more efficient than other methods of digital speech compression. For example, a one minute long speech file which uses other PC audio technology would consume as much as 960 kilobytes. With TrueSpeech, the same file would be just over 60 kilobytes. TrueSpeech is used in the Microsoft Sound System, which also lets you choose the voice sampling you wish when you're recording material. Here is Microsoft Sound System's recording options:


Digital Encoding Rates

Sampling Rate



62K per minute

8 KHz



234K per minute

8 KHz



322K per minute

11 KHz



1291K per minute

22 KHz



5176K per minute

44 Khz


The above is for mono recordings. For stereo, double the amount of space.


A Windows feature. Fonts that are scalable and sometimes generated as bitmaps or soft fonts, depending on the capabilities of your printer. TrueType fonts can be sized to any height, and they print exactly as they appear on the screen. Using TrueType, you'll be able to create documents that retain their format and fonts on any Windows machine.


See True-Up.


  1. In the fall of 1993, AT&T announced that it was introducing new voice quality throughout its long distance network. And that it was calling that quality "true voice." AT&T set up a demo line. Some people thought they could notice an improvement. Some thought they couldn't. I personally thought true voice sounded pretty good.

  2. The trademark name of Centigram's text-to-speech product, which they acquired from SpeechPlus.

Trumpet Winsock

A once-popular Windows 3.xx communications program and TCP/IP stack which allowed people to dial into the Internet and use browsers to surf the Internet. I never liked the program and had great difficulty with it. Fortunately the program has effectively been killed by dial up networking capabilities now part of every Windows 95.

Truncated Binary Exponential Back Off

Another name for exponential back off used in IEEE 802.3 local area networks. In an exponential back-off process, the time delay between successive attempts to transmit a specific frame is increased exponentially.


In data processing, the deletion or omission of a leading or a trailing portion of a string in accordance with specified criteria.


A communication line between two switching systems. The term switching systems typically includes equipment in a central office (the telephone company) and PBXs. A tie trunk connects PBXs. Central office trunks connect a PBX to the switching system at the central office. See also Trunk Side.

Trunk Access Number

  1. The number of the trunk over which a call is to be routed.

  2. The number that needs to be dialed in order to gain access to an outbound trunk. This applies to both local and long distance trunks, as the access number can be different.

Trunk Answer

A phone system feature. This feature allows a ringing call to be answered from any telephone in the system. Typically the feature must be activated in phone system programming.

Trunk Answer From Any Phone

A phone system feature. When a call comes in, something rings. You can now answer the incoming call from any phone. To do so, you must dial a special code or hit a special feature button on your phone. When my office phone system bells ring, all we have to do is to touch "6" on any phone and we can answer the incoming call. Typically the feature must be activated in phone system programming.

Trunk Circuit

An assemblage of electronic elements located in the switching machine.

Trunk Conditioning

Electrical treatment of transmission lines to improve their performance for specific uses such as data transmission. The "tuning" and/or addition of equipment to improve the transmission characteristics of a leased voice-grade line so that it meets the specifications for higher-speed data transmission. Voice-grade lines often have too much "noise" on them. By altering the equipment at both ends of the line, this noise on the line can be overcome . This allows transmission of higher-speed data, which is much more sensitive to noise than voice. See also Conditioning.

Trunk Data Module

TDM. Provides the interface between the DCP signal and a modem or Digital Service Unit (DSU).

Trunk Direct Termination

An option on switchboards which terminates a trunk group on one key (or button) on the console.

Trunk Encryption Device

TED. A bulk encryption device used to provide secure communication over a wideband digital transmission link. It is usually located between the output of a trunk group multiplexer and a wideband radio or cable facility.

Trunk Exchange

A telephone exchange dedicated primarily to interconnecting trunks.

Trunk Group

A group of essentially like trunks that go between the same two geographical points. They have similar electrical characteristics. A trunk group performs the same function as a single trunk, except that on a trunk group you can carry multiple conversations. You use a trunk group when your traffic demands it. Typically, the trunks in a trunk group are accessed the same way. You dial your Band 5 WATS trunk group by dialing 62, for example. If the first trunk of that group is busy, you choose the second, then the third, etc. See Trunk Hunting.

Trunk Group Alternate Route

The alternate route for a high-usage trunk group. A trunk group alternate route consists of all the trunk groups in tandem that lead to the distant terminal of the high-usage trunk group.

Trunk Group Multiplexer

TGM. A time division multiplexer whose function is to combine individual digital trunk groups into a higher rate bit stream for transmission over wideband digital communication links.

Trunk Group Warning

Alerts the attendant when a preset number of trunks in a group are busy. See Trunk Group.

Trunk Holding Time

The length of time a caller is connected with a voice processing system. Defined from the time when the system goes off-hook to the time the port (i.e. the trunk) is placed back on hook.

Trunk Hunting

Switching incoming calls to the next consecutive number if the first called number is busy.

Trunk Make Busy

A fancy name for saying that, by punching a few buttons on the console, you can make any trunks in your PBX or key system busy, effectively putting the trunk out of service. You may want to do this if your trunk is acting up. By busying it out at the console, you are effectively denying its use to anyone in the company. Thus you are protecting yourself from further complaints. Hopefully, it will be repaired promptly.

Trunk Monitoring

Feature which allows individual trunk testing to verify supervision and transmission. You dial an access code and then the specific trunk number from the attendant console. You want the ability to test a specific trunk because normally you might be only accessing a trunk group when you dial an access code. Thus, each time you dial into the trunk group, you might end up on another individual trunk. Some PBXs have a variation of trunk monitoring, whereby if a user encounters a bad trunk, he can dial a specific code, then hang up. The PBX recognizes these digits and makes a trouble report on that specific trunk, possibly reporting it to the operator, keeping it in memory for later analysis or dialing a remote diagnostic center and reporting its agony.

Trunk Number Display

The specific trunk number of an incoming call can be displayed on the attendant console, enabling your attendant to instantly identify the origin of certain calls. For example, if you have several tie lines to branch offices, your attendant knows immediately which office is calling. Many newer PBXs have displays on individual telephones, which show the actual trunk being used for outgoing and incoming calls. This provides an additional measure of control. You might, for example, speak faster if you knew the call was coming in on your IN-WATS line. You might also answer the call differently if you know what trunk it's coming in on. For example, you might be running several, totally-separate businesses from the same console. Each business has a different number. The only way you know what to answer ” Joe's Bakery or Mary's Real Estate ” is by the trunk.

Trunk Occupancy

The percentage of time (normally an hour) that trunks are in use. Trunk occupancy may also be expressed as the carried CCS per trunk.

Trunk Order

A document (or data system equivalent) used in an operating telephone company to request a change to a trunk group.

Trunk Queuing

A feature whereby your phone system automatically stacks requests for outgoing circuits and processes those requests on, typically, a first-in/first-out basis. See Queuing Theory.

Trunk Reservation

The attendant can hold a single trunk in a group and then extend it to a specific phone. This means, for example, that a WATS line can be held for someone special ” a heavy caller, the president of the firm, etc.

Trunk Restriction

Some people may not be allowed to use certain trunks at certain times. The sophistication of trunk restriction depends on the switch and the way it's programmed.

Trunk Segment

The main segment of cable in an Ethernet network is called the trunk segment.

Trunk Side

The portion of a communicating device (phone system, data communications equipment etc.) that is connected to external, i.e., outside plant, facilities such as trunks, local loops, and channels. See also Trunk Side Connection.

Trunk Side Connection

A carrier term. Trunk side connections are within the carrier network. InterMachine Trunks (IMTs) connect carrier switches to other carrier switches. Such switches include circuit switches such as Central Offices (COs) and Tandem switches, Frame Relay switches and routers, packet switches, and ATM switches. End user organizations can lease local loops with trunk side connections, as well; such a loop would appear to the carrier network as being a part of it, and would be used for access to ANI (Automatic Number Identification) information. Compare with Line Side Connection.

Trunk Type

TT. Trunks that use the same type of equipment going to the same terminating location.

Trunk Type Master File

TTMF. An MCI definition. A comprehensive listing of all trunk assignments on the MCI network for shared and dedicated services, necessary for processing and billing MCI customer calls.

Trunk To Tie Trunk Connections

The ability of the switching system to provide the attendant with the capability of extending an incoming trunk call to a tie trunk terminating some place else.

Trunk To Trunk By Station

A PBX feature which permits the user who established a three-way conference involving himself and two trunks to drop from the call without disconnecting the trunk-to-trunk connection.

Trunk To Trunk Connections

The attendant can establish connections between two outside parties on separate trunks. Call your office on your IN-WATS. Ask the operator to extend that call to the VP who happens to be at his home. The operator must place an outside call to the VP on an outside trunk and join that call to the incoming call. Sometimes it works.

Trunk To Trunk Consultations

Allows a phone connected to an outside trunk circuit to gain access to a second outside trunk for "outside" consultation. No conference capability is available with this feature.

Trunk Transfer By Station

Permits the user who established a three-way conference involving two lines to drop from the call without disconnecting the trunk-to-trunk connection.

Trunk Up-Down

See TUD.

Trunk Utilization Report

TUR. A computer printout detailing the traffic use of a trunk.

Trunk Verification By Customer

Provides the attendant or phone user access to individual lines in a trunk group to check their condition. See also Trunk Monitoring.

Trunk Verification By Station

Provides a warning tone if a phone user enters a busy trunk.

Trunked Radio

A system in which users share or pool a number of radio channels. Frequencies are distributed by the system according to demand and traffic levels. Trunking can enhance spectrum efficiency in some circumstances.

Trunked Radio System

Another name for SMR (Specialized Mobile Radio). See SMR.

Trunks In Service

The number of trunks in a group in use or available to carry calls. Trunk in service equals total trunks minus the trunks broken or made busy for any reason.

Trunks Required

The number of trunks that result from interpreting a given offered load against a specified service or economic criterion.

Trust Relationship

The trust relationship is the link between two domains (e.g. two servers on a network) that enables a user with an account in one domain to have access to resources on another domain. The trusting domain is allowing the trusted domain to return to the trusting domain a list of global groups and other information about users who are authenticated in the trusted domain. In the MIS world, a domain is "the part of a computer network in which the data processing resources are under common control." In the Internet, a domain is a place you can visit with your browser ” i.e. a World Wide Web site. See domain and inter-domain trust relationships.


See Class of Service.

Truth Table

An operation table for a logic operation. A table that describes a logic function by listing all possible combinations of input values and indicating, for each combination, the output value.


Transmitter and Receiver (Transceiver). A wireless telecommunications term. A function of the radio channel device for receiving and transmitting signals or information on the radio channel.


Technical Reference number. Technical References are issued by Telcordia Technologies (nee Bellcore). See Telcordia.


  1. Transport Stream. As an ATM term, it is one of two types of streams produced by the MPEG-2 Systems layer. The Transport Stream consists of 188 byte packets and can contain multiple programs.

  2. Traffic Shaping: Traffic shaping in an ATM network is a mechanism that alters the traffic characteristics of a stream of cells on a connection to achieve better network efficiency, while meeting the QoS (Quality of Service) objectives, or to ensure conformance at a subsequent interface. Traffic shaping must maintain cell sequence integrity on a connection. Shaping modifies traffic characteristics of a cell flow with the consequence of increasing the mean Cell Transfer Delay.

  3. Time Stamp: As an ATM term, Time Stamping is used on OAM cells to compare time of entry of cell to time of exit of cell to be used to determine the cell transfer delay of the connection. See also Timestamp.

  4. Transaction Server.


TimeStamp version 3. TS3 is a protocol run on some IRC (Internet Relay Chat) servers for purposes of maintaining their mutual synchronization in support of real-time chats among users on an IRC channel.


See Time-Slot Assignment.


Time Slot Assigner Circuit; a circuit that determines when a CODEC will put its eight bits of data on a RCM bit stream.


Abbreviation for Transport Service Access Point in the OSI transport protocol layer.


Telephony Server Application Programming Interface. Described by AT&T, its inventor , as "standards-based API for call control, call/device monitoring and query, call routing, device/system maintenance capabilities, and basic directory services." For a better explanation, see Telephony Services.


Telecommunications System Bulletin. Interim changes to an interim standard. Not very interesting, but there it is. See IS.


Part of the EIA/TIA-568-A standard. TSB67 describes the requirements for field testing an installed Category 3,4 or 5 twisted pair network cable.


  1. Two-Six Code. A trunk group reference number. The first two characters are alphabet (a-z) and the last six characters are numeric digits.

  2. Transmission Systems Construction.

  3. Technical Service Centers.


Technical Surveillance CounterMeasures. Commonly called debugging, sweeps or electronic sweeping.


Telephony Server. Name of NetWare Telephony Services LAN server which is joined physically (by wire) to an adjacent PBX. See Telephony Services.


  1. Time Slot Interchange or Interchanger. A way of temporarily storing data bytes so they can be sent in a different order than they were received. Time Slot Interchange is a way to switch calls. See Time Slot Interchange.

  2. Transmitting Subscriber Information. A frame that may be sent by the caller, with the caller's phone number, which may be used to screen calls, etc.

  3. Telecommunication System Integration. A fancy name for joining many things together in a telephone system. For example, one part of TSI might be installing Internet Protocol (IP) phone systems into call centers and medium-sized businesses.


Time Slot Interchange Circuit; a device that switches digital highways in PCM based switching systems. In short, a digital crosspoint switch.


Time Slot Interchange Unit. Switching module hardware unit that provides the digital time switching function.


Transmission Security Key.


Terminal Server Manager (TSM), a program that allows terminal servers on a network to be remotely managed from another node. It is supported on VMS systems running the LAT protocol (and is incompatible with TCP/IP-only networks).


  1. Time Share Operation.

  2. Time Sharing Option. An archaic IBM environment for implementing time-shared use of a mainframe computer; operates under IBM's obsolescent OS-based operating system.

  3. Transmission System Operation.

  4. Technical Support Operations.


  1. Telecommunications Service Priority. The TSP System is the regulatory, administrative, and operational system authorizing and providing for priority treatment to provision (initiate) and restore NS/EP (National Security and Emergency Preparedness) telecommunications services. Under the rules of the TSP System, telecommunications companies are authorized and required to provision and restore services with TSP assignments before services without such assignments.

  2. Terminal Service Profile.

  3. Telecommunications Service Provider. A new term for an Internet Service Provider.

  4. Technical Support Planning.

  5. Speed Conversion Table.

  6. Ticket Service Provider. A new term for a web-based company that handles


Traffic Service Position System permits operator positions serving public phones and HOBIC operations to be located remotely from the CO which services the pay phone or the hotel, or the hospital, etc.


  1. Telephone Service Representative. See also Agent.

  2. Terminate and Stay Resident. A term for loading a software program in an MS-DOS computer in which the program loads into memory and is always ready for running at the touch of a combination of keys, e.g. Alt M, or Ctrl ESC. Here's some information from Jackie Fox writing in PC Today: You can't load TSRs willy-nilly and expect them to work with each other. Some will get along with each other. Others won't. When you install a TSR, it goes to a location in RAM (Random Access Memory) called the Interrupt Vector Table.

    The interrupt vector table is like a hotel lobby, and TSRs are like guests waiting for messages. The TSR watches every incoming keystroke to see if it's the special hot key combination (message), the TSR is waiting for. If it isn't, the TSR passes it back to the regular program. What if you have four or five TSRs loaded? The one you loaded last has seniority . It checks the incoming keystrokes first. If the TSR recognizes the keystroke combination as its own hot-key combination, it takes over. If not, it passes it along to the next TSR. This process is called interrupt handler chaining.

    If none of the TSRs recognize that particular combination, they pass it along to DOS so it can process it as a regular keystroke combination. Not all TSRs pass instructions along the way they should. Some TSRs intercept keystrokes and never pass them on. Some TSRs never restore their original addresses. Sometimes two TSRs fight over the same hot key combination. Then you end up with a frozen keyboard. The basic problem is there are no rules for loading and running TSRs.

  3. Terminal Service Representative.

  4. Technical Service Representative.

  5. System Resources Table.

  6. Terabit Switch Router.

  7. Total Service Resale. See Total Service Resale.


Telecommunication Standards Reference Manual.


The Telecommunications Standards Section (TSS) is one of four organs of the ITU. Any specification with an ITU-T or ITU-TSS designation refers to the TSS organ. See ITU.


  1. Time-Space-Time system.

  2. Alarm Steering Table.


Triple Super Twisted Nematic. A display technology often used on laptop computers which uses three layers of crystal to give better contrast and more grey scales .


Transaction Switching and Transport Services. In 1992, the Regional Bell Operating Companies (RBOCs) agreed to provide uniform transaction processing capabilities under a banner called Transaction Switching and Transport Services.


Tone Sender Unit. A device inside a telephone system. The TSU passes along touch- tone digits to telephone extension cards within the phone system. See also TRU (the Tone Receiver Unit) which is used to retrieve and interpret touch-tone data received.


Network Terminal Control Table.


The SYNCHronous test line provides for testing of ringing, tripping and supervisory functions of toll completing trunks. See TNSS.


  1. Trunk Type.

  2. Touch Tone

  3. Transaction Time.


  1. Talking Total Bollocks. This is a European (specifically UK) term coined by telecom experts when noticing a particularly enthusiastic sales guy getting over excited about some new piece of technology. Chris Hall contributed this dubious definition.

  2. Terminal Barring Table.

  3. Touch-tone service (usually for business).


The Telecommunications Technology Committee, a Japanese standards committee.


Tree and Tabular Combined Notation: The internationally standardized test script notation for specifying abstract test suites. TTCN provides a notation which is independent of test methods, layers and protocol.


TestTCP is a test that reports the amount of data transferred, the transfer time, and the approximate throughput. By comparing the actual throughput with the theoretical bandwidth between the transmitter and receiver, you can tell whether the network is operating as expected. To use TTCP, you start a copy of TTCP in receive mode at one place within the network, then start a second copy in transmit mode at another place within the network. The results of the transfer of data from the transmitter to the receiver indicate the approximate performance of the path between the source and destination. By selecting the source and destination at various points with the network, you can analyze critical portions of the path. TTCP has a real advantage over tools like FTP. If you have a high performance network, it is difficult for any single computer system to transfer data to or from disk at rates which are sufficient for real network testing. TTCP achieves high performance by filling a memory buffer with data, then repeatedly transmitting this data. Since everything is running from memory, you have a traffic transmitter and receiver that can operate at true network speeds. Cisco has implemented a copy of TTCP in IOS 11.2 and later, currently as an undocumented command. Since it is undocumented, you will not find it by using the interactive help function. Instead, just type the command ttcp, then press RETURN. If the router model you are using supports TTCP, it will respond with a series of questions for the TTCP parameters. Because TTCP can create enormous amounts of network traffic, it is a privileged command. This gives us a more widely available resource within our networks for generating traffic when performing network analysis and tuning. Because this capability is in the router, we no longer have to install special traffic generators in the network. You'll find that Cisco routers, because they are very efficient at moving IP data, are very good traffic transmitters and receivers. Now you can perform high-speed network traffic analysis without the need for extra equipment. Here's a great explanation (from where I got much of the above explanation):


Temporary Text Delay. The TTD control sequence (STX ENQ) is sent by a sending station in message transfer state when it wants to retain the line but is not ready to transmit.


Transmit Terminal Identification. A fax machine's stupid term for its telephone number and the name of its owner. When you receive a fax from someone, the top line of the fax typically will have a phone number and a name on it. That phone number and name does NOT come from the phone or the phone company. It comes from what the person who owns the machine programmed into his machine. He typically did that by punching buttons on his fax machine. He'll do that if he can understand the instruction booklet which came with his fax (which he probably won't). The point of all this is twofold: First, don't forget to put your name and phone number into your fax machine. Second, don't assume that what you read at the top of any fax you receive is accurate.


Telecommunications Technology Investment Act of 1993.


  1. Transistor Transistor Logic. An internal transfer standard for electronics devices in which a 1 state is +5 Volts and a zero state is 0 Volts; communications systems are sometimes expected to interface to this and provide transmission converters to telecommunications standards.

  2. Time to Live, which is used in IP protocol. It is a time, typically in seconds, after which the fragment can be deleted by any device on the network. Typically this would be used if a router developed an error resulting in a packet that would otherwise circulate for ever. See also Trace Route.


Technical Training and Publications.


Trunk Type Master File.


See Trouble Ticket Modify.


Touch Tone Receiver. A device used to decode touchtones dialed from single-line telephones or Remote Access telephones.


Target Token Rotation Time. An FDDI (Fiber Distributed Data Interface)token travels along the network ring from node to node. If a node does not need to transmit data, it picks up the token and sends it to the next node. If the node possessing the token does need to transmit, it can send as many frames as desired for a fixed amount of time.


Text-To-Speech. A term used in voice processing. See Text-to-Speech.


Tandem Tie Trunk Network.


TeleTYpewriter. Typewriter-style device for communicating alphanumeric information over telecom networks. TTY is the most widely used type of emulation for PC computer communications.


A unique Telecommunication Device for the Deaf, using TTY principles.


  1. Transmit Unit. Term used in a DS-3 channel bank.

  2. Tributary Unit in SDH terminology. Equivalent to a Virtual Channel.


Telecommunications Users Association (UK). The TUA says it aims to support the development of UK businesses through the application of telecommunication and information technologies. It also strives to bring about a fair and competitive market within the UK. TUA holds an annual trade show in the U.K, typically around November or December.


Telecommunications Users Association of New Zealand. A non-profit society of over 500 telecommunications users including major NZ corporations, small to large businesses, government departments, educational institutions and interested individuals. By the way, New Zealand is about as deregulated as you can get; hence, it is a technology test- bed. All the really neat technologies that we now see being introduced in the US have been trialed in New Zealand for years .


TCP and UDP with Bigger Address. One of the three IPng candidates.


Trunk Up-Down. Protocol used in ATM networks that monitors trunks and detects when one goes down or comes up. ATM switches send regular test messages from each trunk port to test trunk line quality. If a trunk misses a given number of these messages, TUD declares the trunk down. When a trunk comes back up, TUD recognizes that the trunk is up, declares the trunk up, and returns it to service. See also Trunk.


Telecommunication User Group.


Telephony User Interface, or Telephone User Interface. A TUI is much like a GUI (Graphical User Interface), except that you use the telephone to get to information in a computer. A TUI makes use of the touchtone keypad to make selections from a menu presented by a voice processor. For example, you might press "1" to speak to an agent about making a domestic flight reservation, "2" for an international reservation, "3" to confirm a reservation, or "4" to order a pizza while you wait for an agent to answer your call. See also GUI.

Tukey, John W.

John W. Tukey was a professor of statistics at Princeton University. Previously, he was a statistician at Bell Telephone Laboratories. Tukey coined the terms "bit" and "software." See also bit and software.


A form of cellular fraud first appearing in late 1990. The crook alters a cellular telephone so that it "tumbles" through a series of ESNs in order to make the caller to appear to be another new customer each time a call is made. By the time the cellular phone network operator has checked with the network where the bogus telephone supposedly is registered and discovered the fraud, the crook has tumbled the telephone, or changed its electronic serial number (typically by one digit) and is ready to make more free calls. As the carriers have moved to IS-41 pre-call validation, this form of fraud has all but been eliminated. See also Clone Fraud.

Tunable Laser

A tunable laser is a component used in fiber-optic systems that can send many different wavelengths of light using fewer parts than conventional lasers. Tunable lasers can tune into more than one wavelength. This allows a single laser to replace the role of up to 16 lasers on a DWDM system. This greatly streamlines DWDM systems and reduces the level of required inventory for back-up purposes (i.e., sparing ). Also called Programmable Laser or Selectable Laser.

Tunable Operating System Parameters

Tuning an operating system is the same as optimizing it, in that you rewrite commands and programs so they operate faster and more efficiently. Any new operating system needs to be tuned to the specific machine on which it is running.

Tuned Absorber Shield

See Microwave Absorber.


A metallic element used in ceramic IC packaging to provide the traces within the package that connect the device circuitry to the external terminals pads or leads.


Adjusting the parameters and components of a circuit so that it resonates at a particular frequency or so that the current or voltage is either maximized or minimized at a specific point in the circuit. Tuning is usually accomplished by adjusting the capacitance or the inductance, or both, of elements that are connected to or in the circuit.


According to the IETF (Internet Engineering Task Force), a tunnel is "An intermediary program which is acting as a blind relay between to connections. Once active, a tunnel is not considered a party to the HTTP communication, though the tunnel may have been initiated by an HTTP request. The tunnel ceases to exist when both ends of the connections are closed." A tunnel is a secure path for communications between clients and servers over an inherently insecure IP-based network. See also Tunneling.

Tunnel Diode

A tunnel diode conducts electricity very well in both directions. However, their resistance to current flowing in the forward direction is very unusual. As the voltage is increased, the current carried by the diode also increases until it reaches a peak. Increasing the voltage beyond the peak value causes the amount of current passing through the diode to decrease! The current will continue to decrease until it reaches a minimum value and then rise again with increasing voltage.


  1. As a local area network term, tunneling means to temporarily change the destination of a packet in order to traverse one or more routers that are incapable of routing to the real destination. For example, to route through a backbone whose internal routers don't contain entries for external destinations, the entry border router must "tunnel" to the exit border router.

  2. As an Internet term, tunneling means to provide a secure, temporary path over the Internet, or other IP-based network, in a VPN (Virtual Private Network) scenario. In this context, tunneling is the process of encapsulating an encrypted data packet in an IP packet for secure transmission across an inherently insecure IP network, such as the Internet. The leading tunneling protocols currently are IP Security (IPsec), Layer 2 Tunneling Protocol (L2TP), Point-to-Point Tunneling Protocol (PPTP), and SOCKSv5. In a typical VPN application, a telecommuter might dial into an ISP (Internet Service Provider). The ISP's router would recognize the request for a high-priority, secure tunnel across the Internet to a corporate gateway router for purposes of access the corporate Intranet. The tunnel would be set up through all the intermediate routers, effectively snaking its way through other, lower- priority Internet traffic. This definition is largely from Ray Horak's book, "Communications Systems & Networks." It's a great book, and a perfect companion to this dictionary. (I wrote one of the forewords for Ray's book. I said pretty much the same thing there, so I guess I'm stuck with that opinion.) See also IP Security, Layer 2 Tunneling Protocol, Point- to-Point Tunneling Protocol, Router, SOCKSv5, Split Tunneling, and Virtual Private Network.

Tunneling Ray

Leaky ray.


Telephone User Part. An SS7 term for the predecessor to ISUP (Integrated Services User Part). TUP was employed for call control purposes within and between national networks, both wired and wireless. ISUP adds support for data, advanced ISDN, and IN (Intelligent Networks). See also ISUP.

Tuple Address

In the Frame Relay (FR) network, packages are sent from switch A to switch B. Each package contains a header section. In the header section of the package, there is information on the DLCI (Data Link Connection Identifier). At switch B, the traffic information is written to a file (based on the Bay Network FR, it is called DATA) every two hours. The billing adjunct processor (AP) will TFTP or FTP the DATA files after it is generated. In each DATA file, it contains the size of the package, number of packages, switch A's IP address (e.g.,, switch A's DLCI (e.g., 1000), switch B's IP address (e.g.,, and switch B's DLCI (e.g., 502). The database of the billing adjunct processor contains the tuple address (switch A's IP & DLCI and switch B's IP & DLCI information) of the circuit that the customer rents. The billing AP converts the DATA files' format to a standard format file and sends it to the billing company which then bills the customer who rents that tuple address. This is very much like our phone bill we receive monthly from a telephone company based on where we called.


Traffic Usage Recorder. A device which connects to a network element in order to capture and record traffic statistics. Most network elements (e.g., PBXs, ACDs, data switches and routers) have special ports to which such a device can connect, usually via a RS- 232 cable. As traffic flows through the network element, various information about that traffic is output to the TUR in real time. The TUR holds that raw data in buffer memory until such time as it is polled by a centralized computer system and the data is downloaded. Subsequently, the data is processed and reports are generated by a traffic analysis application software system. This process of traffic analysis of historical data is essential to the processes of network design and optimization, which balance network performance (avail- ability) against network costs.

Turf Technician

Another term for field technician.

Turing Machine

A mathematical model of a device that changes its internal state and reads from, writes on, and moves a potentially infinite tape, all in accordance with its present state, thereby constituting a model for computer-like behavior. This is the same Alan Turing, British mathematician , who coined the Turing test which I mention under artificial intelligence.

Turbo Coding

A complex data encoding/decoding technique first introduced in 1993 by Messrs. Berrou, Glaviewx and Thitimajshima as an improved means of Forward Error Correction (FEC). Turbo Coding can dramatically improve the BER (Bit Error Rate) of data transmission through an iterative coding/decoding technique, combined with the interleaving/deinterleaving of data blocks. As each block of data is transmitted, it is encoded by two separate convolutional (intertwining) encoders which are concatenated (linked). Commonly, each of the encoders uses the Extended Hamming Code. In each case, the data to be transmitted are organized into data blocks which, for example, are viewed logically as 11 bits horizontal (wide) and 11 bits vertical (deep). To each 11-bit data word, both horizontal and vertical, is appended a 5-bit descriptor before the block is transmitted. This process takes place in each of the two encoders, and the separate results of the processes are intertwined through an "interleaver." At the receiving (Forward) device, two alternating decoders reverse the interleaving process in order to view the separately encoded data blocks. The decoders then recalculate the descriptors, and compare those descriptors with the ones that were calculated and appended by the encoders. Each decoder then is in a position to make a decision about the integrity of each of the bits contained within each of the blocks. Using a technique known as Soft Input-Soft Output (SISO), the decoder also calculates a confidence level (i.e., likelihood ) for each of the decisions (i.e., errored versus unerrored) it has made relative to each of the received bits in each of the blocks. This soft decision-making process is iterative, as the evaluation of each block benefits from the evaluation of each preceding block in a stream of blocks. Think of it as learning from past experience, which must of us consider to be a good thing. While this FEC technique is complex and expensive to implement, it is highly reliable. As the cost of implementing it in silicon (i.e., at the chip level) comes down, it will have increasing application in data networks which are error-prone and bandwidth-limited. For example, Turbo Coding is anticipated to have significant application in deep-space communications and wireless data communications (e.g., CDMA 2000 and UMTS). In both cases, the probability of an error is high. Further, the process of error correction through retransmission is inefficient as bandwidth is limited. In the case of deep space communications, FEC is the only logical alternative, as the time required to retransmit errored data would be excessive, to say the least. See also CDMA, Forward Error Correction, Hamming, SISO, and UMTS.

Turbo FAT

Turbo FAT is an index NetWare v2.2 creates to group all the FAT (File Allocation Table) entries corresponding to a file larger than 262,144KB. The first entry in the turbo FAT index table consists of the first FAT number of the file. The second entry consists of the second FAT number of the file, etc. The turbo FAT enables a large file to be accessed quickly.


A phone fraud term. Turbocharging is the practice of increasing phone charges by adding on extra time onto each call in the hope that the customer won't notice.


The Utilities Reform Network, formerly known as Toward Utility Rate Normalization. A non-profit consumer advocacy that represents the small customer in California, TURN characterizes itself as the only independent, statewide, consumer utility watchdog group. TURN represents residential and small business consumers on utility (e.g., telecommunications and electric power) before the California Public Utilities Commission (CPUC), the state legislature, and the courts.


See Turnkey System.

Turnaround Time

The actual time required to reverse the direction of transmission from sender to receiver or vice versa when using a half-duplex circuit. The turnaround time is needed for line propagation effects, modem timing and computer reaction.


A device used for tightening the tension on guy wires.

Turnkey System

An entire phone or computer system with hardware and software assembled and installed by a vendor and sold as a total package. The term "turnkey" means the buyer is presented with the key to the thing he has just bought. He turns the key and the system will do everything it is supposed to do, including work. Most telephone systems and some computer systems are purchased turnkey. An integral part of a contract to buy a turnkey phone system is the terms and conditions for the acceptance of the system. Someone has to define what it means for the thing to work, what you expect from it ” so you, the buyer, can formally accept the system and thus incur an obligation to pay for it. Defining Acceptance Conditions is no small task on bigger phone systems and more complex computer systems. My advice: always hold some money back as long as you can. This way your contractor will have some incentive to come back and fix what later turns out is not working.


British and Australian term for sales ” typically annual sales.


When a circuit becomes live, it is turned up and working. Turnup is result of completing the installation of a circuit and making it available to the customer who requested it.


A very large key system for financial traders, emergency teams at nuclear power stations and others who need single phone button access to hundreds of people. By simply pushing one button, the user can dial one of hundreds of people. These buttons may be connected to tie lines, foreign exchange lines. They may even be DDD lines with auto- dial capability. Like all good key systems, the buttons have a lamping display which shows if the particular line is idle, busy, ringing, on hold, etc.


Technischer Uberwachungs-Verein. TUV. A German electrical testing and certification organization similar to Underwriters Laboratories (UL). TUV certifies products to European safety standards.


This is an interesting story about the commercialization of the Internet. Tuvalu is a small island nation (constitutional monarchy) comprising nine remote coral atolls with a total land area of 10 square miles, north of Fiji, in the southwest Pacific. The highest point in Tuvalu is 4 meters above sea level. Tuvalu has a population of about 9,000. Its main crops are coconut, taro, pandanus fruit, and bananas. Its exports are postage stamps and copra ( dried coconut meat). Virtually everything is imported. It is a very poor nation, with virtually no telephone service, virtually no utility service (e.g., power, server, water), virtually no medical care, and certainly no Internet access. Tuvalu is a very poor country, and it is expected to be totally under water within the next 50 years, due to the effects of global warming. Tuvalu has absolutely no need for its Internet TLD (Top Level Domain) of .tv. So, the government of Tuvalu on August 11, 1998, sold the rights to ".tv" to the .TV Corporation, a Canadian marketing firm which has established a master domain on the WWW (World Wide Web). Anybody can register a domain name under the .tv domain ” for a price. The total sales price is based on the success of this domain, but revenues to Tuvalu are pegged at a minimum of US$50 million. How's that for e-commerce? See also TLD and Federated States of Micronesia.


Television. See HDTV and Television.


See Trunk Verification by Customer.


TV Linux Alliance. The TVLA is a consortium formed in 2001 by Sun Microsystems, Motorola, Lineo and Liberate. E


Terminal VHF Omni Range.


Television Receive Only Earth Station. Earth station equipment that receives video signals from satellite or MDS-type transmissions. Such stations have only receive capability and need not be licensed by the FCC unless the owner wants protection from interference. Authority for reception and use of material transmitted must be given by the sender.


Bill Gates' new name for a TV with PC smarts.


See Time-Varying Media.

TVM Object

An SCSA definition. An encapsulation of an atomic piece of time-varying media. This encapsulation may be the data itself or a reference to the data.


The tailless dinner jacket was invented in Tuxedo Park, New York. Thus it is called the "tuxedo dinner jacket" and is named after the town...not the other way around. So there.


See Trunk Verification by Station.


Technology Without An Interesting Name. A protocol for communication between software and image-acquisition devices, such as cameras and scanners. It is, in essence, a cross-platform application interface standard for image capturing. It allows you to bring images into imaging programs (like HiJaak Pro, Hotshot Graphics, DocuWare, Documagic) from your graphics hardware ” for example, desktop scanners, hand-held scanners, slide scanners , frame grabbers and digital cameras. If your hardware is TWAIN compliant and if you have installed the correct driver, you should be able to use that imaging hardware with any TWAIN complaint application. The TWAIN protocol is the most popular protocol for imaging sources and has become an industry standard. Any application that supports TWAIN can communicate with any TWAIN-compliant imaging device. TWAIN is spearheaded by Hewlett-Packard, Logitech, Eastman Kodak, Aldus, Caere and other imaging hardware and software vendors. It was previously known as CLASP and "Direct Connect" during its development stage. Apparently the term TWAIN comes from "Toolkit Without An Interesting Name." Despite its silly name, it is a very serious standard. There are several key elements to TWAIN including:

  • Application Layer

    This is the application that controls and uses the TWAIN resource.

  • Protocol Layer

    This contains the TWAIN Source Manager (the code that communicates between the application and the Source).

  • Acquisition Layer

    This is software that controls the image acquisition device. The application layer is developed by the device manufacturer. It can be thought of as a hardware device driver.

  • Device Layer

    This is the physical device, such as a scanner.

TWAIN Working Group

An industry organization dedicated to developing and advancing software standards for the imaging world. See TWAIN.

Tweak Freak

A computer techie obsessed with finding the root of all tech problems, regardless of the relevance. A tweak freak might spend hours trying to track down something that could instantly be fixed by reinstalling the software.

Twenty-three Skiddoo

The famed New York expression, "Twenty-three skid- doo" came to be because the wind drafts created by the height of the skyscraper raised women petticoats, and constables had to "skiddoo" the men who came to peek! See Flatiron Building.

Twin Cable

A cable composed of two insulated conductors laid parallel and either attached to each other by the insulation or bound together with a common covering.


Twinaxial Cable made up of two central conducting leads of coaxial cable. See Twinaxial Cable.

Twinaxial Cable

Two insulated conductors inside a common insulator, covered by a metallic shield, and enclosed in a cable sheath. Because it carries high frequencies, twinaxial cable is often used for data transmission and video applications, especially for cable television.


(pronounced twin-ning.) The act of paralleling systems to work together. An example is connecting a wireless system to the same CO line as a key system, so the user can use either instrument to access the trunk.


A frequency-shift-keyed, carrier telegraphy system in which four unique tones (two pairs of tones) are transmitted over a single transmission channel (such as one twisted pair). One tone of each tone pair represents a "mark," and the other, a "space."


  1. A change, as a function of temperature, in the response characteristic of a transmission line.

  2. The amplitude ratio of a pair of DTMF tones. Because of transmission and equipment variations, a pair of tones that originated equal in amplitude may arrive with a considerable difference in amplitude. In short, signals at different frequencies are transmitted with differing response by the transmission system. Twist usually refers to distortion of DTMF signals.

Twisted Pair

  1. Two insulated copper wires twisted around each other to reduce induction (thus interference) from one wire to the other. The twists, or lays, are varied in length to reduce the potential for signal interference between pairs. Several sets of twisted pair wires may be enclosed in a single cable. In cables greater than 25 pairs, the twisted pairs are grouped and bound together in a common cable sheath. Twisted pair cable is the most common type of transmission media. It is the normal cabling from a central office to your home or office, or from your PBX to your office phone. Twisted pair wiring comes in various thicknesses. As a general rule, the thicker the cable is, the better the quality of the conversation and the longer cable can be and still get acceptable conversation quality. However, the thicker it is, the more it costs. Here's a historical and technical explanation from Ray Horak's best-selling book, Communications Systems & Networks:

    Metallic wires were used almost exclusively in telecommunications networks for the first 80 years, certainly until the development of microwave and satellite radio communications systems. Initially, uninsulated iron telegraph wires were leased from Western Union for this purpose, although copper was soon found to be a much more appropriate medium. The early metallic electrical circuits were one-wire , supporting two-way communications with each telephone connected to ground in order to complete the circuit. In 1881, John J. Carty, a young American Bell technician and one of the original operators, suggested the use of a second wire to complete the circuit and, thereby, to avoid the emanation of electrical noise from the earth ground. This second conductor also supports common Central Office battery; as a result, your phone stills works when the lights go out. Twisted pair involves two copper conductors, which generally are solid core , although stranded wire is used occasionally in some applications. Each conductor is separately insulated by polyethylene, polyvinyl chloride, flouropolymer resin, Teflon, or some other low-smoke, fire retardant substance. The insulation separates the conductors, thereby avoiding shorting the electrical circuit which is accomplished by virtue of the two conductors, and serves to reduce electromagnetic emissions. Both conductors serve for signal transmission and reception. As each conductor carries a similar electrical signal, twisted pair is considered to be a (electrically) "balanced" medium. The twisting process involves the separately insulated conductors being twisted 90 at routine, specified intervals, hence the term twisted pair. This twisting process serves to improve the performance of the medium by containing the electromagnetic field within the pair. Thereby, the radiation of electromagnetic energy is reduced and the strength of the signal within the wire is improved over a distance. Clearly, this reduction of radiated energy also serves to minimize the impact on adjacent pairs in a multi-pair cable configuration, as the other conductors absorb that radiated electromagnetic energy much as an antenna would absorb a radio signal. This is especially important in high-bandwidth applications, as higher frequency signals tend to attenuate (lose power) more rapidly over distance. Additionally, the radiated electromagnetic field tends to be greater at higher frequencies, thereby impacting adjacent pairs to a greater extent. Generally speaking, the more twists/ft., the better the performance of the wire. Several sets of twisted pair wires may be enclosed in a single cable. In cables greater than 25 pairs, the twisted pairs are grouped into "binder groups," which are contained within a common cable sheath. Twisted pair cable is the most common type of transmission media. It is the normal cabling from a central office to your home or office, or from your PBX to your office phone. Twisted pair wiring comes in various thicknesses, or gauges. As a general rule, the thicker the conductor, the better the quality of the conversation and the longer cable can be and still get acceptable conversation quality. However, the thicker it is, the more it costs. Most twisted pair circuits are Unshielded Twisted Pair (UTP). UTP involves no special shielding-just simple insulation. Shielded Twisted Pair (STP) sometimes is used in high-noise environments, where the cable must be run in proximity to electric motors or other sources of ambient electromagnetic interference which can distort the signal. STP looks much like a coaxial cable, as the central conductors are insulated and then surrounded by an outer conductor (shield) of steel , copper alloy, or some other metal. The STP shield absorbs the ambient noise, and conducts it to ground, thereby protecting the center conductor. See also Attenuation, Cat 1-5, STP, and UTP.

  2. Harry Newton and Gerry Friesen are commonly referred to as the twisted pair because their brains don't quite work the way they should.

Twisted-Pair Physical Media Dependent

TP-PMD. Technology under review by the ANSI X3T9.5 working group that allows 100 Mb/s transmission over twisted-pair cable. Also referred to as CDDI or TPDDI.

Twisted-Pair Distributed Data Interface

TP-DDI. Trademark of 3COM Corporation. See Twisted-pair Physical Media Dependent.

Twists Per Foot

TPF. The number of times per foot that the two conductors are twisted around each other in a twisted pair cable system. The twist length, or lay length, is the distance between the twists. For example, a lay length of 3 inches refers to a pair with 4 twists per foot. The more twists per foot, the better the circuit performs, as the twisting process reduces the strength of the electromagnetic field radiated from the circuit. The less energy radiated from the circuit, the more energy remains within it, and the farther the signal will travel without requiring amplification (analog) or regeneration (digital) in order to remain intelligible.


A pregnant goldfish is called a twit. Stupid people are often called twits. I don't know why.

Twitch Game

A computer or arcade game that's all hand-eye coordination and little brain. Similar to "thumb candy ."


Twitchers are birdwatchers in England. In the U.S., they are called birders.

Two Dimensional Coding

A data compression scheme in facsimile transmission that uses the previous scan line as a reference when scanning a subsequent line. Because an image has a high degree of correlation vertically as well as horizontally, two- dimensional coding schemes work only with variable increments between one line and the next, permitting higher data compression. See One Dimensional Coding.

Two Electrode Vacuum Tube

A vacuum tube having a hot cathode and a relatively cold anode, i.e., one with filament and plate only.

Two Hots In Outlets

In AC electrical power, more than one HOT conductor has been incorrectly connected to the terminals in the outlet being tested. Dangers include extreme fire hazard and/or major damage to equipment plugged into the outlet.

Two Out Of Five Code

A decimal code system in which each decimal digit is represented by five binary bits, two of which are ones and three are zeroes.

Two Out Of Three Rule

When determining state tax jurisdiction for the purpose of figuring phone bills, there are three locations to consider: originating station, destination station, and the location that the bill is sent to. If two out of three are the same, then that state receives the tax.

Two Party Hold On Console

Allows an attendant to hold a call with both a calling and a called phone (or trunk) connected. Such a feature is required for activation of Attendant Lockout, Serial Call and Trunk-to-Trunk connections features.

Two Party Station Service

PBX system with two internal phones, each with selective ringing. Resembles rural two party service of old.

Two Pilot Regulation

In FDM systems, the use of two pilot frequencies within a band so that the change in attenuation due to twist can be detected and compensated for by a regulator .

Two Pronged Vampire

Black transformer boxes plugged into AC outlets and attached to things like radios, and laptops are often called two pronged vampires because they often continuously draw power, remaining warm to the touch even when their device ” the radio and the laptop ” are turned off. According to the New York Times, such devices waste about 5% of the power in the U.S., and as much as 10% to 12% in Japan.

Two Stage Shutter Release

A term used in digital photography. A 2-stage shutter release is commonly employed on current electronic cameras. When pressed halfway, the release activates the autofocus and the light meter of the camera, setting them so as to achieve correct focus and exposure. Holding the release at mid-course maintains the focusing point and the exposure parameters (AE Lock) and allows for re-composition if desired. A further press on the shutter release takes the picture.

Two Tier Pricing

A complex and now largely obsolete AT&T pricing plan which imposed two monthly "rate elements" on every hardware piece of an AT&T (now Lucent) telephone system. Tier A was a fixed rate, not subject to rate increases. It was fixed for a certain number of months, say 60. It was, allegedly, to pay for the system. At the end of the 60 months, Tier A disappeared, as though it were a full- payout lease and you now owned the equipment (which you didn't.) Tier B is the second element in this pricing scheme. It covers maintenance, and it is subject to rate increases. Neither AT&T nor Lucent offer two-tier pricing any longer. Many two-tier contracts are now finding their Tier A payments ceasing. Once Tier A payments cease , the equipment still belongs to Lucent.

Two Tone Key

Same as frequency shift keying.

Two Tone Keying

In telegraphy systems, a system employing a transmission path composed of two channels in the same direction, one for transmitting the "space" binary modulation, the other for transmitting the "mark" of the same modulation; or that form of keying in which the modulating wave causes the carrier to be modulated with a single tone for the "marking" condition and modulated with a different single tone for the "spacing" condition.

Two Way Alternate Operation

Transmission in one direction or the other but not in both simultaneously. Most often referred to as half-duplex transmission.

Two Way Simultaneous Operation

Transmission and reception at the same time. More often referred to as full-duplex transmission.

Two Way Splitting

PBX feature. Allows a telephone user to jump back and forth between two calls. Try this: Someone calls you. You both decide you want to speak to a third person. You call that person and conference the three of you together. Then you decide you want to consult with one of the people confidentially. So you "split" one from the other and you speak to one. Then you swap back and forth between the two, speaking to one and then the other in complete privacy. It's easier to do this sort of complicated phone transaction on a phone with a LCD screen. Fortunately, these are becoming more common these days.

Two Way Trade

A call center term. A schedule trade in which both employees are working each other's schedules.

Two Way Traffic

A type of circuit operation that provides for both originating and terminating traffic.

Two Way Trunk

A trunk which can be seized from either end. Can be used to carry conversations into or out of a telephone system, i.e. most trunks. Some trunks are set up as one-way only. A classic one-way trunk is a IN-WATS line. It is designed to only receive calls.

Two Wire Circuit

A transmission circuit composed of two wires ” signal and ground ” used to both send and receive information. In contrast, a four wire circuit consists of two pairs. One pair is used to send. One pair is used to receive. All trunk circuits ” long distance circuits ” are four wire. A four wire circuit costs more but delivers better reception. All local loop circuits ” those coming from a Class 5 central office to the subscriber's phone system ” are two wire, unless you ask for a four-wire circuit and pay a little more.

Two-phase Commit

A method used in transaction processing to ensure data is posted to shared databases correctly by dividing the writing of data into two steps. Each of the steps must receive a verification of completeness from the shared databases; otherwise, the transaction-processing system rolls back the transaction and tries again.


X.3 User ID Conversion Table.


Traveling Wave Tube.


Traveling Wave Tube Amplifier.


(Pronounced TWIX.) Teletype Writer eXchange Service. An automatic teletypewriter (i.e. telex-like) switching service where subscribers may dial any other subscriber and send and receive a message. Formerly owned by AT&T and sold to Western Union in 1972. It differed from Telex in that TWX used AT&T's normal long distance phone network, was thus more ubiquitous, was faster than Telex and was incompatible with Telex, which Western Union owned. However, Western Union, in a major accomplishment, got them to talk to each other.


  1. The designation of a copper RJ-45 connection for Fast Ethernet.

  2. Transmit. See TX/RX for detail.


Transmit/Receive. TX/RX is used to indicate the direction of traffic from the perspective of a device such as a microwave antenna or a router. As an example, a network accounting tool can provide you with traffic statistics over a dial-up modem connection between a network-based router and your client workstation. TX data would be downstream data transmitted from the network-based router to your client, and RX data would be upstream data received by the network-based router from your client. Specific TX/RX traffic measurements might include transmission rates as measured in bps (bits per second), total frame/packet counts, and data (as opposed to signaling and control) frame/packet counts. TX/RX information might also include levels of signal loss, as measured in dB (deciBels), in each direction.


Tycoon comes from the Japanese for "Great Lord."

TYM2 Gateway Interface

The gateway interface between two networks.

TYM2 Protocol

The proprietary protocol used by the TYMNET network.


Tymnet has been billed as one of the first public X.25 packet switched networks. Actually, it is not a true X.25 network but rather an X.25 compliant network using a proprietary OS (operating system). Protocol conversion between the Tymnet OS and X.25 is done at the edge of the network. The name "Tymnet" comes from the fact that this network, like all X.25 packet networks, was established to support timeshare applications. Tymnet was created by Tymshare, spun off as a separate company, then purchased by McDonnell Douglas in 1984. BT (British Telecom) acquired the network in November, 1989; MCI subsequently acquired BT North America, including the North American portion of Tymnet. And MCI was later acquired by Worldcom, which changed its name to MCI Worldcom, which then changed its name back to Worldcom. The X.25 services are still sold by WorldCom domestically in the United States as a bundled service named "Xstream" and sold internationally by Concert Communications (which was a combination of British Telecom and MCI, but then became BT and AT&T) as "Concert Packet Services." If any employee stayed through the various changes over the years, they deserve a major bravery medal. See also Time Sharing.

Type 1 Cable

The IBM Cabling System specification for two-pair, 22 gauge, solid conductor cable protected with a braided wire shield. Tested to 16 Mbps, Type 1 is used between Token Ring MAUs and from the MAU to the wallplate.

Type 1 CLEC

When CLECs have their own network in place, it is referred to as Type 1 Service. In areas where CLECs don't have their own network in place, they lease facilities from the ILEC in order to provide service; this is referred to as Type 2 Service. See CLEC.

Type 2 Cable

The IBM Cabling System specification for a six-pair, 22 gauge shielded cable for voice transmission application. The six-pair version of Type 1 Cable, Type 2 also is tested to 16 Mbps. Typical application is for the two shielded pairs to be used for Token Ring or 10Base-T LANs, with the remaining four pairs being outside the shield and being used for voice transmission. Type 2 is a six-pair equivalent of Category 3 (Cat 3) cable.

Type 3 Cable

IBM's term for telephone wire, Type 3 is single-pair UTP (Unshielded Twisted Pair) wire of 22 or 24 gauge, and involving a minimum of 2 twists per foot. It is used in applications such as 4 Mbps Token-Ring networks.

Type 5 Cable

The IBM Cabling System specification for 62.5/125 micron multi- mode fiber optic cable in a two-pair configuration, which is the de facto standard for FDDI (Fiber Distributed Data Interface).

Type 6 Cable

The IBM Cabling System specification for two-pair, stranded 26 gauge wire used in patch cable applications, as well for connecting LAN station adapters to wall plates. Type 6 is limited to a distance of 30 meters.

Type 8 Cable

The IBM Cabling System specification for untwisted, shielded two-pair, 26 gauge wire. This flat, ribbon cable commonly is used under carpets.

Type 9 Cable

The IBM Cabling System specification for two-pair, shielded, 26 gauge wire, which can be either stranded or solid core. Type 9 Cable accepts RJ-45 termination, and typically is used in connecting from the wall plate to the LAN station adapter.

Type 66 Punchdown Block

A standard, solderless, punchdown terminal wiring block used today. Invented by Western Electric, now Lucent.

Type A

Intelligent Network term describing IN (Intelligent Network) services invoked by, and affecting, a single user. Most of them can only be invoked during call setup or tear- down.

Type Ahead

Imagine a voice processing service. It says "punch in your zip code at the beep." If you are able to punch in your zip code before you hear the beep or before the talking stops, you have "type ahead." If you are unable to punch in your zip code before you hear the beep, you don't have "type ahead." Better interactive voice response systems have "type ahead."

Type Approval

A concept in which a design is approved by an agency and all devices subsequently manufactured according to that design are automatically approved.

Type B

Intelligent Network term describing IN (Intelligent Network) services invoked at any point by, and affecting directly, several users.

Type I PC Card

The thinnest PCMCIA Card from factor at 3.3 mm thick. The Type I format is typically used for various memory enhancements, including RAM, Flash, OTP, SRAM, and EEPROM.

Type II PC Card

A PCMCIA Card which is 5 mm thick. This card is typically used for I/O such as modem, LAN, and host communications.

Type III PC Card

The thickest PCMCIA Card type at 10.5 mm thick, the Type III Format is primarily used for memory enhancements or I/O capabilities that require more space, such as rotating media and wireless communication devices.

Type of Service

TOS. The header of an IPv4 (Internet Protocol version 4), the version currently deployed most widely, contains an eight-bit TOS field. That field can be used to identify to the various packet switches and routers in an IP-based network those packets which would like preferential treatment on a Class of Service (COS) basis. Unfortunately, most switches and routers, and consequently most IP-based networks, currently are unable to support differential levels of service.


Linear type element in a printer containing the printable symbols.

Typing Reperforator

Same as receive only typing reperforator.

Newton[ap]s Telecom Dictionary
Newton[ap]s Telecom Dictionary
ISBN: 979387345
Year: 2004
Pages: 133 © 2008-2017.
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