T 1

See T-1.

T Carrier

T stands for trunk, meaning that the T-Carrier technology was developed for the "trunk side," or carrier side, of the network. In carrier (telco) parlance, the "line side" of the network is the end user, or local loop, side. T Carrier is a generic name for any of several digitally multiplexed carrier systems. The designators for T (Trunk) carrier in the North American digital hierarchy correspond to the broader, generic designators for the digital signal (DS) level hierarchy. To be more exact, the DS level refers to the signal before it enters the channel bank, while the T level signal refers to the signal after it leaves the channel. The T level refers, more than anything else, to the framing convention which is imposed on the information signal by the channel bank. T carrier systems were originally designed to transmit digitized voice signals over a channelized facility. Current applications also include digital data transmission, which generally is transmitted over an unchannelized facility. The table below lists the designators and rates for current T carrier levels, as well as those for E-Carrier (European) and J-Carrier (Japanese).

See T-1 below. Also see DS-, and Channel Bank.

T Connection

T-shaped three-way conductor for distributing an incoming signal in two outgoing ways. Same shape as a T-connection in the road.

T Connector

A T-shaped device with two female connectors and one male BNC connector used with Ethernet coaxial cable and used on local area networks.

T Interface

4-wire ISDN BRI circuit. Picture this: You order an ISDN circuit from your local phone company. They deliver it on a normal phone line ” one copper pair. At your offices, you plug in a small device called a network termination device. That device converts the two-wire circuit called a U interface, into a four-wire S or T interface which you'll use to plug in your ISDN terminal equipment, which might be a phone, a computer, a PBX, a videoconferencing device, etc. It may be all the above. The S or T interface is designed to allow you hook up to eight terminal devices on one ISDN line. Definitions are changing, especially in ISDN. At one stage, the T Interface (more properly the T-Reference Point) needed an NT1 rather than an NT2. These days, some people believe the T interface refers to an ISDN electrical connection to a PBX. While, the S bus refers to a connection to other devices, like phones and videoconferencing devices. There's no electrical difference between an S and a T interface. But I may be proven wrong by some phone company that changes the specs. One of ISDN's most charming features is its ability to acquire different specs and features from one provider to the next . See S Interface and U Interface and ISDN.

T Reference Point

See T Interface.

T Span

A telephone term for a transmission medium through which a T-carrier system is operated. Also called a Span line. See T Carrier and T-1.

T Span Line

Also called a Span line. An outside plant four-wire, two twisted-pair transmission line. See T Carrier and T-1.

T Tap

A passive line interface used for extracting data from a circuit. Also, for extracting optical signals from a fiber cable or electrical signals from a coaxial cable.

T&A

Test and Accept. After a circuit or system is installed, you should test it before you formally accept it. Once the technician walks out the door, it's billable. (Sorry, guys. I know you were expecting another definition. Shame on you.)

T&E

Technology and Evaluation Lab.

T+T

Telephone and Telegraph. I found T+T engraved on a small metal closet in a hotel in Zurich, Switzerland. When I opened the closet, I found a crude telephone line crossconnect panel. The hotel ran its phone lines up a central shaft, terminated them on a crossconnect panel, then ran the lines to each guest room.

T-1

Also spelled T1, which stands for Trunk Level 1. A digital transmission link with a signaling speed of 1.544 Mbps (1,544,000 bits per second) in both directions (i.e. send and receive). T-1 is a standard for digital transmission in North America, ” the United States and Canada. T-1 is part of a progression of digital transmission pipes ” a hierarchy known generically as the DS (Digital Signal Level) hierarchy. (For the complete hierarchy, see the definition for T Carrier above.) In the olden days, T-1 was delivered to your business on two pairs of unshielded twisted copper wires ” one pair for transmit and one pair for receive ” the combination of these two simplex (unidirectional) circuits yields a full duplex symmetrical (bidirectional) circuit. These days, T-1 often is delivered on fiber optic lines, where fiber is available. If it's not available, try and get it. T-1 delivered on fiber typically works better than on copper. You can lease T-1 as a channelized service (delivered as separate voice or data channels), or as an unchannelized raw bit stream (i.e., 1.536 Mbps of transmission both ways, plus .008 Mbps framing bits) and do with the 1.526 Mbps bits as you wish ” the framing bits are not under your control. North American carriers typically deliver T-1 channelized, i.e., split into 23 or 24 voice-grade channels, with each running at 56/64 Kbps (i.e., 56,000 or 64,000 bits per second), depending on the generation of the channel bank equipment involved. If you have need for a bunch of local phones, it's often cheaper to get them delivered on T-1 channels than as individual phone lines. One expensive circuit (i.e, the multi-channel T-1) is far less expensive than 24 less expensive circuits (e.g., single-channel voice circuits). While channelized T-1 was developed for and is optimized for uncompressed voice communications, it also can be used for channelized data communications. A channelized approach is required for access to the traditional PSTN, which is channelized throughout the traditional carrier networks.

On the other hand, an unchannelized approach is better for most data communications applications, and for compressed voice, video and IP telephony. The unchannelized approach provides you with 1.536 Mbps which you can split up any way you choose. If you lease a raw T-1 pipe, you could, for example, split it (i.e., multiplex it) into 12 voice grade channels to support 12 voice conversations, and use the remaining 768 Kbps for either reasonably high-speed access to the Internet or for videoconferencing with your distant office. You could also compress voice to run at speeds of perhaps 8 Kbps or less by using IP Telephony techniques and, therefore, put many more voice calls over a single T-1 pipe. Unchannelized T-1 also is commonly used for access to a frame relay or ATM network, or for Internet access. In such an application, your router or data switch or data concentrator effectively multiplexes data packets (i.e., packets, frames or cells ) through the "clear" pipe. Channelization would make no sense in such an application.

In addition to use in network access applications, T-1 also can be used for private, leased line networking. In a private network, you might use channelized leased T-1 PBX tie trunks to "tie" together your voice PBXs. You might use unchannelized T-1 tie trunks to directly connect your local area network routers or data switches. Note that T-1 is medium-independent. You can run it over electrical (i.e., twisted pair or coaxial cable), optical (i.e., fiber optics or infrared) or radio (i.e., microwave or satellite) transmission media. Outside of the United States and Canada, DS-1 is called E-1, as it was developed by the CEPT (Conference of European Postal and Telecommunications Administrations) for use in Europe. E-1 runs at a total signaling rate of 2,048,000 bits per second. Only one element remains constant between it and the North American's T-1 ” the DS-0, namely the 64 Kbps channel. Most often it represents a PCM voice signal sampled at 8,000 times per second, or 64,000 bits per second. However, the form of PCM encoding, also known as companding, differs between T-1 (mu-law) and E-1 (A-law). Conversion of E-1 to T-1 involves both the compression law and the signaling format. At the higher rate of 2.048 Mbps, 32 time slots are defined at the CEPT interface, but two time slots (channels) are used for non- intrusive signaling and control purposes. The remaining 30 channels are clear 64 Kbps channels for user information-voice, video, data, etc. T-1 is also called 23B+D. That means it can be channelized to contain 23 B channels and one D channel. 30B+2D is compatible with E-1 ” namely it can be channelized to contain 30 B channels and two D channels. See also CEPT, Channel Bank, Companding, Compression, ISDN PRI, PCM, TDM, and Time Division Multiplexing and the following five definitions.

T-1 Card A modern PBX is basically an empty metal cage with a backplane, power and empty slots into which you slide various cards. One of those cards is called a T-1 card. It's used for connecting the PBX to a T-1 line. Typically the T-1 card has a built-in CSU/DSU.

T-1C

Trunk Level 1 Combined. The total signaling rate is 3.152 Mbps in North America and comprises two T-1s, which are interleaved to support 48 DS-0s at 1.544 Mbps each. The additional 64 Kbps is overhead used to support additional signaling and control requirements. T-1C is seldom used, outside of limited telco applications. See T-1.

T-1 BITS interface

See T-1 and BITS.

T-1 Framing

Digitization and coding of analog voice signals requires 8,000 samples per second (two times the highest voice frequency of 4,000 Hz) and its coding in 8-bit words yields the fundamental T-1 building block of 64 Kbps for voice. This is termed a Level 0 Signal and is represented by DS-0 (Digital Signal at Level 0). Combining 24 such voice channels into a serial bit stream using Time Division Multiplexing (TDM) is performed on a frame-by-frame basis. A frame is a sample of all 24 channels (24 x 8 = 192) plus a synchronization bit called a framing bit, which yields a block of 193 bits. Frames are transmitted at a rate of 8,000 per second (corresponding to the required sampling rate), thus creating a 1.544 Mbps (8,000 x 193 = 1.544 Mbps) transmission rate, the standard North American T-1 rate. This rate is termed DS-1. See also D-4 Framing and Extended Super-Frame Format. See also T Carrier, T2, T3 and T4.

T-1 Span Line

See Span.

T-2

The North American standard for DS-2 (Digital Signal Level 2). T-2 operates at a signaling rate of 6.312 Mbps, and is capable of handling 96 voice conversations, depending on the encoding scheme chosen . T-2 is four times the capacity of T-1. It generally is used only in carrier networks, although end users sometimes gain T-2 access on an ICB (Individual Case Basis). An example carrier application is that of SLC-96 (Subscriber Line Carrier 96), which supports 96 voice-grade channels of 64 Kbps over a specially conditioned four-wire circuit. See SLC-96 and T-1.

T-3

The North American standard for DS-3 (Digital Signal Level 3). T-3 operates at a signaling rate of 44.736 Mbps, equivalent to 28 T-1s. T-3 is commonly referred to as 45 megabits per second. Capable of handling 672 voice conversations each at 64 Kbps, T-3 runs on fiber optic or microwave transmission, as twisted copper pair is not capable of supporting such a high signaling rate over distances of any significance. Running on fiber, it is typically called FT-3. Both Bill Gates and George Lucas allegedly have T-3 lines coming into their houses . Sadly, I don't. See T-1.

T-4

The North American standard for DS-4. T-4 supports a signaling rate of 274.176 Mbps and is capable of handling 4,032 voice conversations. T-4 has 168 times the capacity of T-1. T-4 can run on coaxial cable, microwave radio or fiber optic transmission systems. T-4 generally is used only in carrier backbone networks, and generally is not available for end-user consumption. See also T-1.

T-Berd

See T-Bird.

T-Bird

also T-Berd. Colloquial term for a T-1 carrier analyzer, used by T-1 circuit technicians. Taken from the brand name of a leading device, T Berd 90A.

T-I Channel

Either of the two external ports of a TDI or RDI which provides for transmitting or receiving eight TDM channels. Do not confuse with T-1 (as in T-one).

T-ray

Terahertz ray; electromagnetic radiation produced at terahertz (trillion cycles per second) frequencies that, like an x-ray, can penetrate solids, but that also enables the identification of certain molecules and substances. In the June 2000 issue of Technology Review, Herb Brody wrote "Just as x-ray technology came along in the 1890s ” allowing doctors to peer beneath flesh to see bones and organs ” another promising imaging technology is now emerging from an underused chunk of the electromagnetic spectrum: the terahertz frequencies. These so-called t-rays can, like x-rays, see through most materials. But t-rays are believed to be less harmful than x-rays. And different compounds respond to terahertz radiation differently, meaning a terahertz-based imaging system can discern a hidden object's chemical composition. Potential applications range from detecting tumors to finding plastic explosives. And since t-rays penetrate paper and clothing, a terahertz camera could detect hidden weapons." In the February 2004 issue of MIT Technology Review, the ediors wrote, "With the human eye responsive to only a narrow slice of the electromagnetic spectrum, people have long sought ways to see beyond the limits of visible light. X-rays illuminate the ghostly shadows of bones, ultraviolet light makes certain chemicals shine , and near-infrared radiation provides night vision. Now researchers are working to open a new part of the spectrum: terahertz radiation, or t-rays. Able to easily penetrate many common materials without the medical risks of x-rays, t-rays promise to transform fields like airport security and medical imaging, revealing not only the shape but also the composition of hidden objects, from explosives to cancers."

T-SM

An ADSL term for the functional interface between the ATU-R (Asymmetric Transmission Unit-Remote) and the PDN (Premises Distribution Network). The ATU-R may contain one or more T-SMs (Service Modules) for terminal adaption. The T-SM may be the same as the "T" interface where the PDN is a point-to-point, passive cable and wire system. The T-SM may be a separate physical device, or may be embedded in an integrated ATU-R/SM. See also ADSL, ATU-R, PDN, SM and T.

T.120

The most important transmission protocol standard for document conferencing (viewing, changing and moving files) over transmission media ranging from analog phone lines to the Internet. T.120 is the International Telecommunications Union (ITU-T) standards suite for document conferencing via FTP (File Transfer Protocol). Virtually all major players in the document conferencing industry have announced support for this standard. Document conferencing adds a visual dimension to voice-only conference calls by allowing groups of people to share computer documents in real-time while participating in a standard voice conference call. Whatever materials would normally be distributed in a face-to- face meeting ” graphs, spreadsheets, diagrams, or documents ” can be shared on-line, in real-time. Participants can easily connect to a conference anywhere in the world, with the only requirements being a Windows PC, a modem and a document conferencing software program. T.120 series standards provide a framework to enable multi-point data conferencing across LANs, WANs and the Internet. The T.120 architecture relies on a multilayered approach with defined protocols and service definitions between layers. Each layer presumes the existence of all layers below. The lower level layers (T.122, T.123, T.124 and T.125) specify an application-independent mechanism for providing multi-point data communications services to any application that can use these facilities. The upper level layers (T.126 and T.127) define protocols for specific conferencing applications, such as shared whiteboarding and binary file transfer. See also H.320, standards which extend data conferencing into video conferencing.

T.121.

ITU standard for generic T.120 Application Template.

T.122

Multipoint Communications Service for Audiographics and Audiovisual Conferencing - Service Definition. (ITU approved 1993.) See T.120 and T.125.

T.123

Protocol Stacks for Audiographics and Audiovisual Teleconference Applications. (ITU approved 1993/1994.) See T.120.

T.124

Generic Conference Control for Audiovisual Services (GCC) (ITU voted approval in 3/95.) T.125: Multipoint Communication Service - Protocol Specification (MCS). (ITU approved 1994.) See T.120 and T.122.

T.125

Multipoint Communication Service - Protocol Specification (MCS). (ITU approved 1994.) See T.120.

T.126

Provides shared whiteboard and document conferencing protocols. See T.120.

T.127

Provides multipoint binary file transfer. See T.120.

T.128

ITU standard for Audio Visual Control for Multipoint Multimedia Systems.

T.134

See T.140.

T.140

In early February, 1998, the ITU-T reported that it had just completed work on three recommendations aimed at enhancing the capability of the deaf or speech-impaired to use telecommunications. The first recommendation, V.18, describes a multi-function text telephone that bridges the gap that has, according to the ITU, between several incompatible text telephones in use today. The second (T.140) adds new facilities to enable the use of different alphabets and character sets in text communications. These include Arabic, Cyrillic and Kanjii, as well as Latin-based characters . Finally, T.134 describes how these facilities can be integrated in the multimedia communications systems defined by the ITUT.

T.30

ITU-T standard. Fax handshake protocol. This standard describes the overall procedure for establishing and managing communication between two fax machines. There are five phases of operation covered: call set up, pre message procedure (selecting the communication mode), message transmission (including phasing and synchronization), post message procedure (end-of-message and confirmation) and call release (disconnection).

T.35

ITU-T recommendation proposing a procedure for the allocation of ITU-T members ' country or area codes for non-standard facilities in telematic services.

T.37

An ITU-T Recommendation for store-and-forward fax via e-mail through the incorporation of SMTP (Simple Mail Transfer Protocol) and MIME (Multipurpose Internet Mail Extension). SMTP is an application-layer extension of TCP/IP which governs electronic mail transmissions and receptions. MIME is a SMTP extension which supports compound mail. In this context, MIME provides for the attachment of a compressed fax image to an e-mail. Fax image documents are attached to e-mail headers and are encoded in the TIFF-F (Tagged Image File Format-Fax) compressed data format. In simple-mode, T.37 restricts fax transmission to the most popular fax machine formats (e.g., standard or fine resolution, and standard page size ). This restriction is done through limitation of TIFF-F encoding to the S-profile. Simple mode provides no confirmation of delivery. Full-mode extensions include mechanisms for ensuring call completion through negotiation of capabilities between the transmit and receive devices. Full-mode also provides for delivery confirmation. This definition is from "Communications Systems & Networks," Ray Horak's best-selling book. Ray is Contributing Editor of this dictionary. See also MIME, SMTP, T.30, T.38, and TIFF.

T.38

An ITU-T Recommendation for store-and-forward fax via e-mail. Derived from X.25 packet standards, T.38 addresses IP fax transmissions for IP-enabled fax devices and fax gateways, defining the translation of T.30 fax signals and Internet Fax Protocol (IFP) packets. The specific methods for various T.38 implementations include fax relay and fax spoofing. Fax relay, also known as demod/remod, addresses the demodulation of standard analog fax transmissions from originating machines equipped with modems, and their remodulation for presentation to a matching destination device. Fax relay depends on a low latency IP network (i.e., one second or less) in order that the session between the fax machines does not time out. Fax spoofing is used for fax transmissions over IP networks characterized by longer and less predictable levels of packet latency that could cause the session with the conventional fax machines to time out. Packet transmission over such a network can result in variable levels of delay of packet receipt, packet-by-packet, which timing phenomenon is known as jitter. Compensation for both the longer level of delay and the jitter are accomplished by padding the line with occasional keep- alive packets to keep the session active, rather than allowing it to time out. The receiving device is spoofed, or fooled, into thinking that the incoming transmission is over a realtime, carefully timed voice network. Delays up to five seconds can be tolerated in this manner. T.38 provides for two transport protocols, User Datagram Protocol (UDP) and Transmission Control Protocol (TCP). UDP is the faster of the two, but the less reliable, as no error detection and correction is included at the network level. T.38 overcomes this shortcoming either through redundant transmission of the image data packets, which is inherently inefficient at the network level, or through a Forward Error Correction (FEC) technique, which is inherently inefficient at the device level. TCP includes an error correction mechanism employed at the router level, with the routers typically being positioned only at the edges of the network- switches typically are positioned in the core of the network. Although T.38 strips this process from consideration for the IP fax packets, the level of delay nonetheless is increased; thereby, spoofing techniques are required to maintain fax sessions. This definition is from "Communications Systems & Networks," Ray Horak's best-selling book. Ray is Contributing Editor to this dictionary. See also Fax Relay, Fax Spoofing, FEC, T.30, T.37, TCP/IP, UDP, and X.25.

T.4

ITU-T standard for Group 3 fax machines, using T.30 and various V series standards. It also describes the data compression methods MH and MR.

T.434

The concept is simple: use a fax machine equipped with a disk drive to send and receive binary files as easily as you send a fax. The system would benefit from the fax's technical sophistication and ease of use, such as calling tone and the called unit's identification of capabilities. T.434 is an evolving ITU-T recommendation which defines a format used to encode a binary file and its attributes into a set of octets. This encoded binary file can then by sent over phone lines using error-corrected T.30 fax pages. The union of these two elements (file format and T.30 ECM) is known as "Binary File Transfer." The T.434 file attribute encoding is independent of ECM's block and page segmentation. T.434 defines 27 attributes which are used to describe a file. These attributes include protocol version, filename, permitted actions, contents type, storage account, date and time of creation, date and time of last modification, date and time of last read access, identity of creator, identity of last modifier, identity of last readers, filesize, future filesize, access control, legal qualifications, private use, structure, application reference, machine, operating system, recipient, character set, compression, environment, pathname, user visible string and data file content. Fisk Communications of San Diego, CA has done extensive work in the area of T.434 and has granted an irrevocable royalty-free and compensation free license to the Telecommunications Industry Association for basically all Fisk's work on T.434. Fisk hopes to make T.434 an extensive standard so that its equipment, which sends binary file transfers, can communicate with and receive from other machines.

Microsoft also has defined a binary file transfer in the fax portion of its Microsoft At Work architecture. Some observers believe the At Work binary file transfer architecture is richer and more robust than T.434, supporting password and public/private-key encryption as well as digital signature verification. As of writing, it is not clear which standard will win.

T.568A

T.568A Is a wiring scheme used for terminating four pair, all category 5e cable. There are three main choices when deciding which wiring scheme to use. The T.568A can accommodate two pair voice (2 pair USOC Voice Wiring)) and also 10Base-T networks, while the T.568B can only handle one pair voice. The other wiring scheme would be USOC wiring, used only when wiring for voice (Not recommended).

T.568B

See T.568A.

T.6

ITU-T recommendation for Group 3 fax machines using T.30 and various V series standards. It also describes compression methods (Modified Huffman and Modified READ).

T.611

Also known as Appli/Com. A messaging standard proposed by France and Germany defining a Programmable Communication Interface (PCI) for Group 3 fax, Group 4 fax, teletex and telex service.

T1

See T-1.

T1.5

Same as T1. Se T1.

T1.601

The ANSI specification for ISDN BRI outside wire, known as the U interface. T1.601 uses the 2B1Q line code operating at 160 Kb/s (144 Kb/s of 2B+D plus Layer 1 overhead bits). The electrical signal can tolerate a maximum loss of 42 dB at 40 KHz, which usually limits the local loop length to 18 Kft or less.

T11

A technical committee of the National Committee for Information Technology Standards , titled T11 I/O Interfaces. It is tasked with developing standards for moving data in and out of central computers.

T1

1. A committee accredited by ANSI and sponsored by the Alliance For Telecommunication Industry Solutions (ATIS). The committee's role is to establish U.S. standards for digital telephony, particularly T1. ATIS provides all the administrative and logistical support. See Alliance for Telecommunications Industry Solutions.

2. See T-1 above (as in T-ONE).

T1 Multiplexer

A statistical multiplexer that divides the 1.544MbpsT1 bandwidth into 24 separate 64Kbps channels of digitized data or voice.

T1 Small Aperture Terminal

TSAT. A small satellite terminal used for digital communications that can handle T1 data rates of up to 1.544Mbps.

T1 Y1 (J1) E1

Voice channels, digitized and combined into a single digital stream. T1s are 1.544 Mbps. Y1 and E1 are similar in bandwidth and are used in Japan and Europe respectively.

T1-606/T1-6ac/T1-gfr

ANSI's frame relay service specifications.

T-120

See T.120

T1C

3.152 million bits per second. Capable of handling 48 voice conversations. T1C is further up the North American digital carrier hierarchy. See T CARRIER and T-1.

T1D1

This is the specific technical subcommittee within CCITT responsible for ISDN standards.

T1E1.4

An ANSI committee studying emerging the creation of a new high bit-rate digital subscriber line standard. The technology promises to deliver symmetric 1.544 Mbps data rates (i.e. T-1 speeds) to distances of up to 12,000 feet using the American National Standards Institute's T1E1.4/99-006 draft standard for a single pair T-1 transport. With single pair transmission (T-1 over copper wires has always been transported over two pairs, one pair for receive and one pair for transmit), the cost of provisioning and maintaining a T-1 line will drop dramatically. The big push to develop T1E1.4 have been North American telephone companies, who see a huge demand for high speed data. But they see their future in delivering it on fiber. Meantime, they have a huge investment in copper pairs. So let's figure a technology to use those copper wires. Bingo the big interest in T1E1.4. See HDSL and HDSL2.

T1E1

An ANSI standards sub-committee dealing with Network Interfaces.

T1M1

An ANSI standards sub-committee dealing with T-1 Inter-Network Operations, Administration and Maintenance.

T1Q1

An ANSI standards sub-committee dealing with performance.

T1S1

T1S1 is a technical subcommittee to T-1 responsible for standards related to services,architectures, and signaling.

T1X1

T1X1 is a technical subcommittee to T-1 responsible for standards pertaining to synchronous interfaces and hierarchical structures relevant to interconnection of network transport signals.

T2

6.312 million bits per second. Capable of handling at least 96 voice conversations depending on the encoding scheme chosen. T-2 is four times the capacity of T-1. T-2 is further up the North American digital carrier hierarchy. In this dictionary we have adopted the style of writing T2 as T-2. See T-1.

T3

Twenty eight (28) T-1 lines or 44.736 million bits per second. Commonly referred to as 45 megabits per second. Capable of handling 672 voice conversations. T-3 typically runs on fiber optic and is then called FT3. T-3 is further up the North American digital carrier hierarchy. In this dictionary we have adopted the style of writing T3 as T-3. Some people believe that FT3 also means fractional T3. See T-1.

T3POS

Transaction Processing Protocol for Point of Sale. T3POS is a transaction switching and transport protocol designed to provide existing Point-Of-Sale (POS) equipment and future POS terminals with efficient and economical switching and transport service over an X.25 based packet network.

T4

274.176 million bits per second. Capable of handling 4032 voice conversations. T-4 has 168 times the capacity of T-1. T-4 can run on coaxial cable, waveguide , millimeter radio or fiber optic. T-4 is further up the North American digital carrier hierarchy. In this dictionary we have adopted the style of writing T4 as T-4. See also T-1.

TA

1. Terminal Adapter. A Terminal Adapter allows existing non-ISDN terminals to operate on ISDN lines. It provides conversion between a non-ISDN terminal device and the ISDN user/network interface. See Terminal Adapter.

2. Technical Advisory. These publications are documents describing Bellcore's preliminary view of proposed generic requirements for products, new technologies, services, or interfaces.

3. Termination Attempt.

4. Telecommunication Administration.

TAB

Technical Application Bulletin.

Table

1. A collection of data in which each item is arranged in relation to the other items. Many telephony functions use "look up tables" to determine the routing of calls. These tables solve the problem, "If the call is going to this exchange in this area code, then use this trunk and this routing pattern." See Table Driven.

2. The major design tool of most web pages. Let's say you want to design a web page with two photos next to each other, separated by words talking about the photos. The only way to design this into a web page is to set it up with a table with three columns ” two for the photos and one for your text.

Table Driven

Describing a logical computer process, widespread in the operation of communications devices and networks, in which a user-entered variable is matched against an array of pre defined values. Frequently used in network routing, access security and modem operation. It involves a table look up that is a reference to a collection of pre defined values.

Table Hook-Up Method

An information retrieval system in which the input information and the related output information are stored as a pair. When a particular input is given, the table is accessed and the output data which coincides with the input is taken out.

Table Stable

A large one-room office that's filled with worktables but has no partitions. In short, it's a cube farm with the cubes, i.e. the cubicles.

Tablet PC

Imagine the screen of your laptop being your portable PC. You'd have a screen larger than your PDA that would weigh less than your laptop. You'd touch icons or handwrite on the screen ” just like you do on your PDA. But you wouldn't have a builtin keyboard, though you might be able to plug one in. Personally I don't see the tablet PC's advantages, but then I don't carry either a PDA or a wireless pager.

TABS

AT&T's Telemetry Asynchronous Block Serial protocol. A polled point-to-point or multi point " master-slave " (remote-monitored equipment) communication protocol that supports moderate data transfer rates over intra office wire pairs. The remotes send " requests " or " polls " to monitored equipment. The monitored equipment answers the request with "responses." Defines two physical interfaces for direct connection between the telemetry remote and the monitored equipment:

• R5422 Point-to-Point

• RS485 Point-to-Point or Multi-Point. Four wire, two Tx (remote to monitored) and two to Tx (monitored to remote), 22 or 21 gauge twisted pair, max 4 kft remote-to-monitored.

TAC

Test Access Controller.

TACACS

Terminal Access Controller Access Control System. An IETF (RFC 1492) standard security protocol which runs between client devices on a network and against a TACACS server. TACACS is an authentication mechanism which is used to authenticate the identity of a device seeking remote access to a privileged database. Variations on the theme include TACACS+, which provides services of authentication, authorization and accounting independently. TACSAS+ supports a challenge/response system and password encryption, as well as the standard TACACS user authentication. See also Authentication.

TACS

Total Access Communications Systems. The original analog cell phone system system launched in 1985 by Vodafone. Used in the U.K., China, Asia, Japan, and Italy, TACS is also called ETACS, ITACS, IETACS, NTACS, and JTACS. It operates using FDMA. TACS was short-lived. TACS is a derivative of AMPS (Advanced Mobile Phone System), the analog cellular standard developed by Motorola and widely deployed in the U.S. and other parts of the world. TACS operated in the 900 MHz band , supporting 1,000 voice grade channels. TACS gave way to GSM, which is a much better digital technology. JTAC (Japanese TACS), which operated in the 800 and 900 MHz ranges, suffered a similar fate. See also AMPS and GSM.

TACT

Trend Analysis for Circuit Troubles.

Tactical Automatic Digital Switching System

TADSS. A transportable store-and-forward, message-switching system designed for rapid deployment in support of tactical forces. A military definition.

Tactical Command And Control (C2) Systems

The equipment, communication, procedures, and personnel essential to a commander for planning, directing, coordinating, and controlling tactical operations of assigned forces pursuant to the missions assigned. A military definition.

Tactical Communication

A military term. A method or means of conveying information of any kind, especially orders and decisions from one command, person, or place to another within the tactical forces, normally by means of electronic equipment (including communications security equipment). Excluded from this definition are communications provided to tactical forces by DCS, to non tactical forces by DCS, to tactical forces by non tactical military commands, and to tactical forces by civil organizations.

Tactical Communication System

A system configured by various types of fixed-size , self-contained assemblages, such as radio terminals and repeaters; switching, transmission, and terminal equipment; and interconnect and control facilities, that are used within or in support of tactical military forces. The system provides securable voice and data communications and among mobile users to facilitate command and control within, and in support of, tactical forces.

Tactical Data Information Link

TADIL. A military term. A Joint-Chiefs-of- Staff-approved standardized communication link suitable for transmission of digital information. A TADIL is characterized by its standardized message formats and transmission characteristics.

Tactical Data Information Link ” A

TADIL ”A. A military term. A netted link in which one unit acts as a net control station and interrogates each unit by roll call. Once interrogated, that unit transmits its data to the net. This means that each unit receives all the information transmitted. This is a direct transfer of data and no relaying is involved.

Tactical Data Information Link ” B

TADIL ”B. A military term. A point-to-point data link between two units which provides for simultaneous transmission and reception of full duplex data.

Tactical Load

A military term. That part of the operational load required by the host service consisting of weapons, detection, command control systems, and related functions.

TAD

Telephone Answering Device.

TADIL

Tactical Data Information Link.

TADSS

Tactical Automatic Digital Switching System.

TAF

Targeted Accessibility Fund. In the late Spring of 1998, the New York State Public Service Commission ordered the establishment of a Targeted Accessibility Fund (TAF), which, according to the NYPSC, "will fund the costs incurred by all local exchange carriers, including competitive carriers, for E-911, lifeline and telecommunications relay service. All telecommunications carriers will be required to contribute to the fund based upon their intrastate gross revenues net of payments made to underlying carriers...Under PSC guidelines, the TAF is to be administered by a ten person board."

TAFAS

Trunk Answer From Any Station. The ability to answer an incoming phone call from any telephone attached to the system.

TAFKAP

The Artist Formerly Known As Prince. In 1993, Prince Rogers Nelson, the rock artist known as "Prince" was engaged in a contract dispute with Warner-Chappel, his former record label. To spite them and thereby hopefully affect their sales of his records, he changed his name to an unpronounceable symbol. Therefore, he became known as "The Artist Formerly Known As Prince," i.e. TAFKAP. On December 31, 1999, his contract with Warner-Chappel formally expired . On May 16, 2000, TAFKAP announced to an anxiously- awaiting world that he was changing his name back to "Prince."

Tag

1. A field in a cache that contains information that allows determination whether a word in the cache corresponds to a requested word.

2. Tags are codes used for formatting HTML documents for the World Wide Web. There are both single and compound tags. For example, the single code for a line break is <br>. Bold text requires compound tags. For example, if you want to bold the word help, you would mark it <b>help</b>, where <b> means to turn on bolding and </b> means to shut it off.

3. See RFID Tag.

Tag and Locate

I first heard about this "definition" from BellSouth. Apparently a technician goes to a business and locates where multiple lines come in and tags them for identification purposes.

Tag Image File Format

TIFF provides a way of storing and exchanging digital image data. Aldus Corp., Microsoft Corp., and major scanner vendors developed TIFF to help link scanned images with the popular desktop publishing applications. It is now used for many different types of software applications ranging from medical imagery to fax modem data transfers, CAD programs, and 3D graphic packages. The current TIFF specification supports three main types of image data: Black and white data, halftones or dithered data, and grayscale data. Some wags think TIFF stands for "Took It From a Fotograf." It doesn't.

Tag Switching

A technique developed by Cisco Systems for high-performance packet forwarding through a router. A label or "tag" is assigned to destination networks or hosts . As a packet stream is presented to the tag edge switch, it analyzes the network- layer header prepended to each packet, selects a route for the packet from its internal routing tables, prepends the PDU with a tag from its Tag Information Base (TIB), and forwards the packet to the next-hop tag switch, which typically is a core tag switch. That core switch then forwards the packet solely on the basis of the tag, eliminating the need to re-analyze the header. As the packet reaches the tag edge router at the egress point of the network, the tag is stripped off and the packet is delivered to the target device. While this approach adds a small amount of overhead to each packet, the speed of packet processing is improved considerably, particularly in a complex network in which multiple routers or switches must act on each packet. Tag switching can be applied to IPX and other network protocols, as well as IP. Tag switching also allows Layer 2 switches to participate in Layer 3 routing, reducing the number of routing peers with which each edge router must deal, and, thereby, enhancing the scalability of the network. Tag switching was submitted to the IETF (Internet Engineering Task Force), where it became the basis for MPLS (MultiProtocol Label Switching). See also MPLS.

Tagged Traffic

ATM cells that have their CLP bit set to 1. If the network is congested , tagged traffic can be dropped to ensure the delivery of higher-priority traffic. Sometimes called DE traffic. See also CLP.

TAI

inTernational Atomic tIme. See International Atomic Time.

Tail

An echo cancellation term. The tail, measured in milliseconds, is the amount of your conversation which returns to you in the echo, as measured in milliseconds. A tail of zero milliseconds clearly means there's no echo.

Tail Circuit

1. A feeder circuit or an access line to a network. Typically, a connection from a satellite, microwave receiver to a user's equipment location.

2. A point-to-point circuit connecting a remote terminal to a local terminal via two modems at an intermediate site. A crossover cable connects the two modems at the intermediate site.

3. A communications line from the end of a major transmission link, such as a microwave link, satellite link, or LAN, to the end-user location. A tail circuit is a part of a user-to-user connection.

Tail-End-Hop-Off

TEHO. In a private network with several nodes (locations), TEHO occurs when a call placed from one location on the network to a location not on the network leaves the network at the node closest to its destination.

Tailgating

See Employee Tailgating.

Tailing

In facsimile systems, the excessive prolongation of the decay of the signal. Also called Hangover.

Take Back and Transfer

See Callback.

Take Ownership

A new term for the old expression, to take charge. In this case, there's a project that needs to be done, let's say building a new factory. Someone has to be in charge. Someone has to "take ownership." In normal business, to take ownership usually involves being in charge of something smaller ” for example making sure that the hot dogs are delivered to the company picnic.

TALI

Tekelec Adaptation Layer Interface. Official Tekelec words: Tekelec developed the Transport Adapter Layer Interface (TALI) to fulfill an industrywide need for an open interface to ensure interoperability of convergence solutions from multiple vendors. In December 1999, Tekelec released the TALI interface source code to the telecommunications and Internet industries in an effort to promote an open network architecture for signaling over IP. With the support of Level 3, U S WEST Wireless, Lucent, Cisco, Orange PCS, and other carriers and equipment suppliers that are currently using the interface, Tekelec has submitted TALI to the Internet Engineering Task Force (IETF) for consideration as a standard.

Talk

A service on Internet whereby you hold conversations with others by typing into your computer. And they reply by typing into their computer.

Talk Battery

The DC voltage supplied by the central office to the subscriber's loop so as to allow you to have a voice conversation. Also known as A BATTERY. Typically somewhere between 5 and 25 volts . See B Battery.

Talk Off

In voice processing, in response to questions such as "Press one for Harry," the user touchtones buttons on his phone. Those buttons generate DTMF (Dual Tone Multi- Frequency) tones. The system has to figure out what the person "said" with his touch- tones. The tricky part of DTMF detection is distinguishing between tones generated from an actual "key press" and "tones" caused by speech. Mistaking a person's speech (as in leaving a message) for DTMF is called "talk-off." Mistaking a person's recorded speech (as in playing back a message) for DTMF is called "play-off."

You can imagine the havoc poor DTMF detection can cause a voice processing system. For example, if touchtoning three means "delete this message" and while playing the message, the system incorrectly detects a portion of the message playback as the touchtones for a key press three, I'll delete the message when I had intended to listen to it. On the other hand, if I'm listening to a message and want to delete it prior to finishing the message, I want the system to detect my key press three as the real thing and go ahead and delete the message.

Talk Path

The tip and ring conductors of a telephone circuit.

Talk Set, Optical

An instrument for talking over fibers ” used when installing and testing the cable.

Talk Time

1. The amount of time agents spend on the phone, as opposed to the time between calls spent updating records, sending out literature or going to the bathroom.

2. The length of time you can talk on your portable or transportable cellular phone from a fully charged battery without standby time. The battery capacity of a cellular portable or transportable is usually expressed in terms of so many minutes of talk time or so many hours of standby time. When you are talking, the phone draws more power from the battery.

Talk-Off

See Talk Off.

Talkdown

Missed signals in the presence of speech. Commonly used to describe the performance of a DTMF receiver when it fails to recognize a valid DTMF tone due to cancellation of that tone by speech.

Talker

Provides interaction with a Dialogic board, allowing for Voice Mail functionality.

Talk Battery

DC current supplied from the central office to power the transmitter of the subscriber's telephone set. See Battery.

Talking Battery

See Battery and Talk Battery.

Talking Channel Capacity

TC. The network access line capacity of talking channel equipment of an entity is the maximum number of network access lines that can be served without exceeding the percent incoming matching loss objective for that entity .

Talking Head

That part of the person seen in the typical business videoconference; the head and shoulders. This type of image is fairly easy to capture with compressed video because there is very little motion in a talking head image.

Talkoff

See Talk Off.

TAM

1. Telephone Answering Machine.

2. Telecommunications Access Method.

3. Total Available Market. A cable TV word that refers to all the houses in the neighborhood of the cable.

Tamper Detection

In encrypted messaging, tamper detection allows the recipient of information to verify that it has not been modified in transit. Any attempt to modify data or substitute a false message for a legitimate one will be detected . See Public Key Encryption.

Tandem

In a telecommunications context, the term refers to switches, circuits, or other Network Elements (NEs) that serve to allow other NEs to work together. For example, tandem switches, or tandem offices, serve to interconnect other, lesser switches, i.e., Central Offices (COs) or lesser tandems. Tandem switches, in the purest sense of the term, serve no end users directly, as that is the responsibility of the COs. Rather, they strictly serve to interconnect the COs, which are at the lowest level of the switching hierarchy in the PSTN (Public Switched Telephone Network). Tandem tie trunks serve to interconnect tandem switches. See the following definitions.

Tandem Access Trunk Groups

A category of trunk groups that originates at EOs (End Offices) and terminates at tandems.

Tandem Architecture

A physical network topology where connectivity between locations is achieved by linking several locations together in a chain using private line circuits. In a tandem architecture, a packet may have to pass through several intermediate locations before reaching its final destination. A single network failure can affect connectivity between several locations, a primary weakness of the topology.

Tandem Call

A call processed by two or more switches. Also used to designate this type of call at a switch where a connection is established from one trunk to another (tandem trunking). See Tandem Switch.

Tandem Center

In a communication system, an installation in which switching equipment connects trunks to trunks, but not any customer loops .

Tandem Completing Trunk Groups

A category of trunk groups that originates at tandems and terminates at EOs.

Tandem Connecting Trunk

TC Trunk. A 1- or 2-way trunk between an end office switching system and an LATA tandem switching system.

Tandem Data Circuit

A data channel passing through more than two data circuit-terminating equipment (DCE) devices in series. At the relay point, transmitted and received data, clock and other control signals must be transposed; if not accomplished in a switching system, a cable between the two must do so, often called a "rollover cable," or "null modem." See Null Modem Cable.

Tandem InterLATA Connecting Trunk

TIC Trunk. The trunk used for switched LATA access that interconnects an long distance company's Point of Presence (POP) with an local phone company's switching system. See Direct InterLATA Connecting Trunk Group.

Tandem Office

A major phone company switching center for the switched telephone network. It serves to connect central offices when direct interoffice trunks are not available.

Tandem PBX

A main PBX is one which has a Directory Number (DN) and can connect PBX stations to the public network for both incoming and outgoing calls. A main PBX can have an associated satellite PBX, and can be part of a Tandem Tie Trunk Network (TTTN). If the main PBX provides tandem switching for tie trunks, it is called a tandem PBX.

Tandem Point

An intermediate location in a tandem architecture.

Tandem Queuing

A telephone company term. When for example: A shortage of receivers in a terminating office will be reflected in originating offices trunking traffic into the terminating switch. The obvious effect will be a slowing down of the originating office transmitters, i.e., Tandem Queuing.

Tandem Switch

Tandem is a telephony term meaning to "connect in series." Thus a tandem switch connects one trunk to another. A tandem switch is an intermediate switch or connection between an originating telephone call location and the final destination of the call. The tandem point passes the call along. A PBX can often handle tandem calls from other/to other locations as well as process calls to, from and within its own location.

Tandem Switching System

Synonym of Tandem Tie Trunk Network.

Tandem Tie Trunk Network

TTTN. A serving arrangement that permits sequential connection of tie trunks between PBX/CENTREX locations by utilizing tandem operation. TTTNs are large, private switched networks, generally used by the federal government, state and county governments , and the military to interconnect sites (e.g., government buildings , and military posts and bases). The tandem switches can be either totally dedicated switches, or partitions of switches also used for the PSTN (Public Switched Telephone Network). See also AUTOVON.

Tandem Tie Trunk Switching

The PBX permits tie lines to "tandem" through the switch. This means an incoming tie line call from a distant PBX receives a dial tone instead of automatically connecting with the operator. The caller can then dial a connection with either a phone on the PBX or an outgoing line. The outgoing line can be a local trunk in which case the distant PBX has access to a form of foreign exchange service, or another tie line which links a third system. This system of tie lines is widely used to form a corporate communications system, allowing economical connections between distant offices. To provide tie line tandeming ability, the PBX must be able to detect when either tie line goes on-hook at the distant end so that it can break its tandem connection and allow the tie lines to be used for other calls.

Tandem Trunks

Trunks between an end office and a tandem switching machine or between tandem switching machines. Tandem trunks can provide direct routing or alternate routing capability when direct trunks are occupied.

Tangerine

A stock that is trading for less than the sum of its parts. Its value can be found (perhaps) by breaking it into juicy segments.

TANDM

Traffic Analysis Data Management.

Tank Test

A voltage dielectric test in which the wire or cable test sample is submerged in water and voltage is applied between the conductor and water as ground.

TANSTAAFL

There Ain't No Such Thing As A Free Lunch.

Tantalum

See Coltan and Tantalum Capacitor.

Tantalum Capacitor

A Tantalum Capacitor is a device circuit switched equipment that processes voice calls from central offices. See Trunk Exchange.

TAO

1. The creative principle that orders the universe, according to Taoists, who follow the mystical Chinese philosophy founded by Lao-tzu (also spelled Lao-tse) in the 6th century B.C. Tao also is the path of virtuous conduct conceived by Confucians. In our context, "Tao" is both a set of principles which guide standards processes, and a set of rules of order or conduct which guide the participants in the processes. The Internet Engineering Task Force (IETF) and other standards bodies use "Tao" in order to avoid using terms like "rules," which its participants might find offensive. If you are a "Nethead" or if you know any "Netheads," you can relate to this. The IETF actually writes "Pronounced 'dow,' Tao is the basic principle behind the teachings of Lao-tse, a Chinese master. Its familiar symbol is the black and white Yin-Yang circle. Taoism conceives the universe as a single organism, and human beings as interdependent parts of a cosmic whole. Tao is sometimes translated 'the way,' but according to Taoist philosophy the true meaning of the word cannot be expressed in words." In August, 2001 the IETF published "The Tao of IETF: A Novice's Guide to the Internet Engineering Task Force." You can read this long document at http://www.ietf.org/tao.html#8.2

2. Telephony Application Object. Part of the SCSA programming framework. See S.100 and SCSA Telephony Application Objects Framework.

Tap

1. An electrical connection permitting signals to be transmitted onto or off a bus. The link between the bus and the drop cable that connects the workstation to the bus. Also a device used on CATV cables for matching impedance or connecting subscriber drops .

2. Telocator Alphanumeric Protocol, also known as IXO. A 7-bit messaging protocol which allows someone sitting at a terminal or computer to send a one-way message to a pager (also known as a beeper ). TAP is ACSII-based and half-duplex. TAP provides an error detecting link from the sender to the paging service provider. See also IXO and SNPP.

3. A term in video compression referring to the number of pixels or lines considered in the process of averaging values through the filtering process. MPEG uses a 7-tap filter.

4. To draw energy from a circuit.

Tap Button

A button found on single line phones behind a PBX or Centrex. The tap button gives a precisely measured Hookswitch flash. The purpose of this button is to signal the PBX that it is about to receive a command ” typically a transfer. To transfer a call on a single line phone, you typically depress the hookswitch, then punch out the extension you want to transfer the call to, announce the call when someone answers, then hang up and the PBX or Centrex transfers the call. The problem with using a hookswitch to make this transfer is that if you depress the hookswitch for too long you will cut the call off. As a result, some manufacturers put a tap button on their single line phones. This button gives the precise hookswitch signal for the precise length of time necessary ” no more, no less. The Tap Button is also called a Flash button or a Tap Key.

Tap Key

Also called Tap Button or Flash Key. A button on a phone that accomplishes the same function as a switch hook but is not a switch hook. See Tap Button.

Tap Loss

In a fiber optic coupler, the ratio of power at the tap port to the power at the input port.

Tap Port

In a coupler where the splitting ratio between output ports is not equal, the output port containing the lesser power.

TAPAC

Terminal Attachment Program Advisory Committee. Body which recommends telecom standards to the Canadian Federal Government.

Tape Bomb

Troubling news that scrolls across the bottom of CNBC, Bloomberg TV and CNNfn, catching investors off guard and without time to sell (or buy).

Tape Drive

The physical unit that holds, reads and writes magnetic tape.

Tape Reader

A device which reads information recorded on punched paper tape or magnetic tape.

Tape Relay

A method of retransmitting TTY traffic from one channel to another, in which messages arriving on an incoming channel are recorded in the form of perforated tape, this tape then being either fed directly and automatically into an outgoing channel, or manually transferred to an automatic transmitter for transmission on an outgoing channel.

Tapeout

Tapeout is a term used in the semiconductor business. When a processor or other silicon product is "taped out," all the various components that are necessary for it to function are complete. It marks the end of development of the product and the beginning of manufacturing. The term "tape out" itself is an anachronism, recalling the era when a design was actually transferred to magnetic tape in data form. The tape, in turn, was given to mask design to produce a "mask" or blueprint that was then used to manufacture the product. Today, tapeout means generating the final files for silicon masks. These masks are then shipped (or electronically transferred) to a mask making unit.

Tapered Fiber

An optical fiber in which the cross section, i.e., cross-sectional diameter or area, varies, i.e., increases or decreases, monotonically with length.

TAPI

Telephone Application Programming Interface. Also called Microsoft/Intel Telephony API. A term that refers to the Windows Telephony API. TAPI is a changing (i.e. improving) set of functions supported by Windows that allow Windows applications (Windows 3.xx, 95 and NT) to program telephone- line-based devices such as single and multi-line phones (both digital and analog), modems and fax machines in a device-independent manner. TAPI essentially does to telephony devices what Windows printer system did to printers ” make them easy to install and allow many application programs to work with many telephony devices, irrespective of who made the devices. TAPI is one of numerous high-level device interfaces that Windows offers as part of the Windows Open Services Architecture (WOSA). TAPI simplifies the process of writing a telephony application that works with a wide variety of modems and other devices supported by TAPI drivers. See also Dial String, Microsoft Fax, TAPI 2.0, TAPI 3.0, Windows 95 and Windows Telephony for fuller explanations .