The Internet has opened a new world of commerce through electronic transactions. To keep unsavory characters that prowl the alleys and byways of cyberspace from stealing important, sensitive information that is sent across a network, secure socket layer (SSL) is used to provide authentication, encryption, and message integrity services. Secure socket Layer, a transport level technology for authentication and data encryption between a Web server and a Web browser, i.e. sending documents around the Internet and the Web. Developed by Netscape, SSL negotiates point-to-point security between a client and a server. SSL sends data over a "socket," a secure channel at the connection layer existing in most TCP/IP applications. Both Netscape Navigator and Internet Explorer support SSL, and many Web sites use the protocol to obtain confidential user information, such as credit card numbers . By convention, Web pages that require an SSL connection start with https : instead of http:. You can recognize the secure nature by the S. In short, SSL is the dominant security protocol for Internet monetary transactions and communications. Information being transmitted is encrypted, and only the user's Web browser and the computer server at the other end running the Web site have the key, and thus can understand what each other is saying. But no one else can. See also S-HTTP.


Speech Synthesis Markup Language is a VXML (Voice eXtensible Markup Language) language for text-to-speech markup. See also VXML.


Subsystem Number. The address used in the Signaling Connection Control Part (SCCP) layer of the SS7 protocol to designate an application at an end signaling point. For example, an SSN for CNAM (Calling Name ) at the end office designates the CNAM application within the end office. Usually, the SSN is a three digit number. BellSouth happens to use a CNAM SSN of 232.


See Single Sign-On.


Service Switching Point. Also called Signal Switching Point. A PSTN switch(End Office or Tandem) that can recognize IN (Intelligent Network) calls and route and connect them under the direction of an SCP (Service ControlPoint. A computer database that holds information on IN (IntelligentNetwork) services and subscribers. The SCP is separated from the actual SCP switch, making it easier to introduce new services on the network. See SCP. For a full explanation of the Advanced Intelligent Network, see AIN.


Simple Server Redundancy Protocol. The LANE simple server redundancy feature creates fault-tolerance using standard LANE protocols and mechanisms.


Spread Spectrum Technology. See Spread Spectrum.


  1. Switched Services Transport Protocol. See SCTP.

  2. Double-Shielded Twisted Pair, as in Shielded-Shielded Twisted Pair. Also known as PiMF (Pairs in Metal Foil). A cabling system involving multiple twisted pairs contained within the same cable sheath. Each twisted pair is separately shielded by a metallic foil. The entire group of shielded pairs is then surrounded by another shield of metallic braid or foil. See also Category 7.


Session Support Utility. a DEC-proprietary protocol that allows multiple sessions to run simultaneously over a single serial cable. SSU is used to allow terminals to provide two session " windows " that can display session output simultaneously.

SSUTR2 Utilisateur T l phonie RNIS. This French national SSUT standard for the SSUT+ was defined in 1986 by the ETSI. SSUTR2 and Telephone User Part + (TUP+) are closely related . The French TUP is the interface between fixed and mobile, using SS7.


  1. STart signal to indicate end of outpulsing.

  2. Straight Tip. A fiber- optic connector designed by AT&T which uses the bayonet style coupling rather than screw on as the SMA uses. The ST is generally considered the eventual replacement for the SMA type connector.

  3. Signaling terminal.

ST Connection

An optical medium connector plug and socket.

ST Connector

See Straight-Tip Connector.

ST-506/412 Interface

One of several industry standard interfaces between a hard disk and hard disk controller. The "intelligence" is on the controller rather than the drive.


Serial Telecom Bus. Mitel Semiconductor, which makes telecom componentry, has structured its digital component product line around the ST-BUS. The ST-BUS is a high speed, synchronous serial bus for transporting information in a digital format. Whether the digital information is voice, data, or video ” or a mixture of each ” the ST-BUS is designed to accommodate it. The ST-BUS consists of one or several serial data streams with a framing signal and clock signals. The framing signal always has a period of 125 us, resulting in 8,000 frames per second, with the original ST-BUS clock rate of 2.048 Mbit/s (thirty two 64 kbit/s channels). The ST-BUS standard now includes higher speed modes of 4.096 or 8.192 Mbit/s ST-BUS, resulting in 64 or 128 channels of 64kbit/s, respectively. This provides the bandwidth necessary for newer multimedia applications. According to Mitel, the advantages of using the ST-BUS are:

  1. Printed circuit board area devoted to information transfer between functional modules is minimized.

  2. Fewer tracks, backplane connections, and intra-shelf cables are needed compared to systems that use parallel paths.

  3. The ST-BUS is designed to be divided down into individual channels of 64 kbit/s, resulting in improved efficiency and lower cost when several information paths are able to share the same ST-BUS.

  4. Additional glue logic is not required when using ST-BUS compatible components .

  5. From an IC perspective, the ST-BUS results in lower pin counts, improved reliability, and less power consumption.


  1. Spanning Tree Algorithm. A technique based on an IEEE 802.1 standard that detects and eliminates logical loops in a bridged network. When multiple paths exist, STA lets a bridge use only the most efficient one. If that path fails, STA automatically reconfigures the network so that another path becomes active, sustaining network operations.

  2. Special Temporary Authority. A special temporary authority granted by the FCC to operators of Public Mobile Services (e.g., cellular radio and Specialized Mobile Radio, or SMR) "upon a finding that there are extraordinary circumstances requiring operation in the public interest and that delay in the institution of such service would seriously prejudice the public interest." See also IOA and SMR.


A set of data storage locations that are accessed in a fixed sequence. The list of internal instructions being executed by a computer is known as a "stack," just like the one made of trays at the start of a cafeteria line. When you add an instruction, you "push" it onto the stack; you remove an instruction with a "pop," just like you're taking off a tray.


A term referring to devices/system the capacity of which can be increased through connecting (daisy-chaining) the device to additional devices. Thereby, it is not necessary to increase device/system capacity through a complete replacement, often known in the telephone equipment business as a "forklift upgrade." LAN hubs and switches are often stackable. Such devices often can be interconnected ( stacked ) in a wiring closet, See also Daisy Chain, Forklift, and Scalable.

Stackable Hubs

Single protocol units designed to link various hubs, thereby effectively creating one large interconnected local area network (LAN). See Stackable.

Staffing Basis

A call center term. The basis upon which staffing requirements are calculated. Can be either desired service quality for a given day of the week or the number of staff that will product the highest net revenue.

Staffing Requirements Forecast

A call center term. A calculation of the number of employees required in each period of the day to handle the forecast call volume for that period.

Stage & Test

A term used in the secondary telecom equipment business. The installation (stage) and diagnostic testing of a PBX switch, cabinet, part, or peripheral in a reconfiguration center facility ” where a dealer tests the complete system as one entity before shipment.

Stage Phoning

Pretending to talk on a cell phone to impress bystanders. As British researcher Sadie Plant noted, "Some mobile users tend to make a virtue of the lack of privacy of stage phoning." This definition from Wired Magazine.


In facsimile systems, periodic error in the position of the recorded spot along the recorded line.

Stair Stepping

  1. Using a low-level account to gain ever-higher levels of unauthorized access in a network.

  2. Video term. Jagged raster representation of diagonals or curves; correctively called anti-aliasing.

Stalker Site

A Web site created by an obviously obsessed fan. "Have you seen that Gillian Anderson stalker site? The guy's got like 200 pictures of her!" A Wired Magazine definition.


Corporate stakeholders, a termed coined by SAP, include employees, customers, partners and shareholders. As business competition intensifies and planning cycles speed up, corporations will need to keep all these constituents informed and involved, Kevin McKay, CEO of SAP America Inc. said in September, 1998. "We need to communicate with every stakeholder because this will open up new opportunities," McKay said.

Stand Alone

Any device that can perform independently of something else.

Standalone ACDs

These Automatic Call Distribution switching systems are designated specifically for the call center environment. Characteristics include non-blocking capacity, high- powered CPUs, comprehensive real-time and historical management reports , and programmable call routing and treatment routines. They are standalone because they are separate pieces of equipment. Another way of providing ACD service is through a telephone company central office ” in which case it would not be "standalone."


Standard is a Middle English term (from Old French, and with Germanic origins) meaning something such as a specification established as a yardstick, gauge, or criterion by authority, custom, or general consent . A de jure standard is a formal standard, a de facto standard is a standard without formal authority, and a d'jour standard is one enjoying current and temporary popularity. See also D'jour, De Facto, and De Jure.

Standard Industrial Classification

SIC. The classification or segmentation of businesses that are increasingly finite based on 2, 4, 6 or more digit identifiers. Developed by the U.S. Department of Commerce in the early 1960's.

Standard Industry Practice

Terminology used to indicate normal rules used within the secondary telecom equipment business. These rules have developed over time and usage, but lack formal support by industry groups or dealers. In short, there is no clear definition as to what "standard industry practice" means in the secondary business.

Standard Jack

The means of connecting Customer premises equipment to a circuit as specified in the FCC Registration Program.

Standard Metropolitan Statistical Area

SMSA. A metropolitan area consisting of one or more cities as defined by the Office of Management and Budget and used by the FCC to allocate the cellular radio market.

Standard Test Zone

A single-frequency signal with a standardization level generally used for level alignment of single links in tandem.

Standardized Test Tone

A single frequency signal at a standardized power level.


Agreed principles of protocol. Standards are set by committees working under various trade and international organizations. RS standards, such as RS-232-C are set by the EIA, the Electronics Industries Association. ANSI standards for data communications are from the X committee. Standards from ANSI would look like X3.4-1967 which is the standard for the ASCII code. The ITU (now called the ITU-T) does not put out standards, but rather, publishes "recommendations", owing to the international egos involved. "V" series recommendations refer to data transmission over the telephone network, while "X" series recommendations, such as X.25 (properly pronounced "Eks dot twenty five"), refer to data transmission over public data networks. Notice that the ANSI standards have the year they were approved as part of the name of the standard, while ITU recommendations do not. The placement of the "dot" is another clue as to whose confusing standard belongs to whom.

When you're buying a phone system, at minimum it should conform to four standards:

  • Emissions compliance according to the FCC Part 15.

  • Telephone compliance according to the FCC Part 68.

  • Safety standards set by the National Electric Code, OSHA and the Underwriters Laboratories 1459.

  • Bellcore compliance (from the Network Equipment Building System publication and their Generic Physical Design Requirements for Telecommunications Products and Equipment publication. See Standards Bodies. The US Standard railroad gauge (distance between the rails) is 4 feet, 8.5 inches. That's an exceedingly odd number. Why was that gauge used? Because that's the way they built them in England, and the US railroads were built by English expatriates . Why did the English people build them like that? Because the first rail lines were built by the same people who built the pre- railroad tramways, and that's the gauge they used. Why did "they" use that gauge then? Because the people who built the tramways used the same jigs and tools that they used for building wagons, which used that wheel spacing. Okay! Why did the wagons use that odd wheel spacing? Well, if they tried to use any other spacing the wagons would break on some of the old, long distance roads, because that's the spacing of the old wheel ruts. So who built these old rutted roads? The first long distance roads in Europe were built by Imperial Rome for the benefit of their legions. The roads have been used ever since. And the ruts? The initial ruts, which everyone else had to match for fear of destroying their wagons, were first made by Roman war chariots. Since the chariots were made for or by Imperial Rome they were all alike in the matter of wheel spacing. Thus, we have the answer to the original questions. The United State standard railroad gauge of 4 feet, 8.5 inches derives from the original specification for an Imperial Roman army war chariot. Specs and Bureaucracies live forever. So, the next time you are handed a specification and wonder what (expletive deleted) came up with it, you may be exactly right. Because the Imperial Roman chariots were made to be just wide enough to accommodate the back-ends of two war horses.

Standards Bodies

See the Appendix at the back of this dictionary.

Standby Monitor

In a Token Ring network, a network node that serves as a backup to the Active Monitor and can take over in the event that the Active Monitor fails.

Standby Processor

A spare computer exists which can direct PBX operations if the primary one fails. Some standbys are just sitting there, installed but not turned on. They require someone to turn them on. Some standbys are actually running all the time, as the main one is. If the main one crashes, the standby processor is ready to take over.

Standby Time

The amount of time you can leave your fully charged cellular portable or transportable phone turned on to receive incoming calls before the phone will completely discharge the batteries. See Talk Time.

Standing Wave

When you look at it on an oscilloscope the pattern of the wave is perfectly flat, i.e. horizontal. It's caused by two sine waves of the same frequency moving in opposite directions. In transmission line theory the accepted definition is simply the superposition of two waves traveling in opposite directions.

Standing Wave Ratio

SWR. The ratio of the amplitude of a standing wave at an anti-node to the amplitude at a node.


  1. A topology in which all phones or workstations are wired directly to a central service unit or workstation that establishes, maintains and breaks connections between the workstations. Virtually all phone systems are stars configurations. ISDN BRI bus will be the first phone system to operate on a bus. In datacom language, the center of a star is called the hub. The advantage of a star is that it is easy to isolate a problem node. However, if the central node fails, the entire network fails. The star network we're all most familiar with is our local telephone exchange. At the center (the hub) rests the central office. Spanning out in a star are the lines going to the individual workstations (telephones) in peoples' houses and offices.

    click to expand
  2. Advanced telecommunications for the industrially less advanced regions of the European Community.

Star Button

The star button on the touchtone phone is often used to mean "No" in interactive voice response or computer telephony systems.

Star Coupler

A device that couples multiple fibers at a central point and distributes the signal from one fiber into all others simultaneously.

Star Network

A computer network with peripheral nodes all connected to one or more computers at a centrally located facility.

Star Quadded Cable

Spiral-four cable. See Star Network.

Star Topology

A LAN topology in which end points on a network are connected to a common central switch by point-to-point links. See Star.


An obsolete local area network developed by AT&T using twisted pair telephone wires in a star configuration.

Start Bit

In asynchronous data communications, characters are sent at arbitrary intervals, i.e. when the operator hits a key. In order for the computer to make heads or tails of what's coming in, each character starts its transmission with a Start Bit. This way, if the first bit of the character to be transmitted is a 1, the fact of receiving a Start Bit (always a 0) tips off the computer that the next bit is part of a transmitted character and not just part of the inter-character gap. See Stop Bit.

Start Element

  1. The start pulse of a transmission character. It is used for synchronization of the following bits in a serial transmission process.

  2. One of the input or output points in a communications system. This would include a telephone set, a data terminal, a computer communications port.

Start Of Heading

SOH. A control character used in data communications that designates the beginning of the message header.

Start Of Heading Character

SOH. A transmission control character used as the first character of a message heading.

Start Of Message

SOM. A control character used in data communications that designates the beginning of the message.

Start Of Text

STX. A control character used in data communications that designates the beginning of the information being transmitted.

Start Stop Transmission

The technique of asynchronous data transmission wherein each character is comprised of a start element at its beginning and a stop element at its end. Start-stop elements allow the receiving device to determine where the transmitted bits for one character ends and the next begins.

Start Time Interval

A call center term. A scheduling rule that governs the times at which schedules can start; for example, at 15-minute intervals as opposed to 30-minute intervals.


Informal for STATistical MUltipleXor.


  1. The condition of a connection within a telephone call that reflects what the past action on that connection has been and that determines what the next set of actions may be.

  2. The instantaneous properties of an object that characterize that object's current condition. See State Machine Programming.

State Machine Programming

To control multiple telephone lines in a single voice processing program, a new program structure is required. Dialogic calls this technique state machine programming. Computer Science called state machines "Deterministic Finite State Automata."

State Public Service Commission

PSC. The State legislative body responsible for among other things, regulating the operation of telephone companies and other persons involved in the furnishing of telephone service. Some states' PSCs are called Public Utilities Commissions. See the next definition.

State Signal

In MF pulsing , a signal used to indicate that all digits have been transmitted.

State Tax

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.

State Transition

The act of moving from one state to another.

State Utility Commissions

Each state has a utility commission responsible for the regulation of telephone service provided wholly within that state. Regulation extends to introduction of new services, their prices, who will provide them, as well as discontinuance of existing services.


Protocols that maintain information about a user's session. FTP is a stateful protocol. Stateless is the opposite.

Stateful Inspection Firewall

A stateful inspection firewall examines the contents of individual packets at all layers of the OSI model, from the network layer to the application layer. To perform this task, this firewall relies on packet-filtering algorithms to examine and compare each packet against known bit patterns of authorized packets.

Stateful Packet Inspection

See SPI and Stateful Inspection Firewell.


Protocols that do not maintain information about a user's session. Each transmission is considered a new session. HTTP is a stateless protocol.


  1. In computer programming languages, a language construct that represents a set of declarations or a step in a sequence of actions.

  2. In computer programming, a meaningful expression or generalized instruction represented in a source language.


  1. Unchanging. Fixed.

  2. Interference caused by natural electric disturbances in the atmosphere, in your office, in your home. Static electricity can play havoc with telephone systems, computers, sound systems, in short anything electronic. Properly grounding your phone system to a true cold water pipe (not one that connects to a PVC plastic pipe) is the most minimal protection. Walk across a nylon carpet in your plastic shoes, touch something. You'll see a blue spark jump between you and what you touched. That blue flash can be thousands of volts . That blue flash can damage sensitive electronics. That's why factory workers always wear static electricity straps. These straps fit around their wrists and attach to a ground somewhere close by. That way any static electricity they generate will go to ground through the strap not through the valuable electronics they are touching.

Static Document

A static document is one that doesn't change. Basically all web site are designed to send you static pages written in a language called HTML. If you want an updated version of that page, you have to ask your browser to refresh the page. Some web sites will feed you dynamic (i.e. changing) information but you typically have to have some software running on your computer. A simple browser won't cut it. Solutions are coming.

Static IP Address

See Dynamic IP Address and IP Address.

Static Object

Information that has been pasted into a document. Unlike embedded or "linked" objects, static objects cannot be changed from within the document. The only way you can change a static object is to delete it from the document, change it in the application used to create it, and paste it into the document again.

Static Positioning

Location determination when the GPS (Global Positioning System) receiver's antenna is presumed to be stationary in the earth. This allows the use of various averaging techniques that improve the accuracy of figuring where you are by factors by over 1000.

Static RAM

Static Random Access Memory chips do not require a refresh cycle like Dynamic RAM chips and thus can be accessed well over twice as quickly. Static RAM chips must have power to maintain the data they are holding. Static RAM chips cost more than Dynamic RAM chips, which are also called D-RAM.

Static Route

A route that is manually entered into a routing table. Static routes take precedence over routes chosen by all dynamic routing protocols. See Static Routing.

Static Routing

Static routing involves the selection of a route for data traffic on the basis of routing options preset by the network administrator. Dynamic routing, on the other hand, adjusts automatically to changes in network topology or traffic. Dynamic routing automatically accomplishes load balancing, therefore optimizing the performance of the network "on the fly." Dynamic routing is more effective, but the routers are more costly and the more complex decision-making process imposes additional delays on the subject packet traffic. In addition to being less costly, static routing offers enhanced security. As there is only a single, pre-programmed route, it is impossible to bypass a security mechanism such as a firewall. See also Link State Routing, Distance Vector Routing, Path Vector Routing Protocol, and Router.

Static Wire

A grounded wire at the very top of a telephone or utility pole intended to protect lower conductors (i.e. telephone, CATV, etc.) from lightning. See Joint Pole.


  1. A semi-dumb word for a telephone. Also called an instrument, or a telephone instrument. An extension station is one connected "behind" a PBX or key system. In other words, the PBX or key system is between the station and the telephone central office. Howard Pena, a reader of my dictionary, wrote me that he had heard a story (several times) that the telegraph system in the US was based on a network of telegraph wires strung between railroad stations . When the telephone system reached the American frontier, the most efficient way to install it was to replace each telegraph with a telephone. So, when you placed a call, you were calling a station. If that's true, Station is not a "dumb word for a telephone." The opposite is true. It's a strong reminder that without the PBX, we'd all be standing in line to use the village telephone.

    Ray Horak did "a good bit of research on this, but can't verify Howard's story." Makes sense, however. I agree with his criticism of the current definition. The dictionary defines "Station" as a stopping place. It's used in many contexts, including railroads, power transmission, and the bible (stations of the cross). Also used to describe a place established to provide a public service, e.g., fire station and police station.

    For my taste, I suspect the word "station" comes from the very old days when regulation of the telephone industry was taken over by the Interstate Commerce Commission, (the ICC), which also at that time regulated the railroad industry.

  2. A shortened word for workstation ” a name for a PC on a LAN.

Station Adapters

Cables and interface assemblies for connecting Dialogic network interface and switching products to telephones or analog telephone lines.

Station Apparatus

The equipment which is installed on the customer's premises, including phones, ancillary electronics and small hardware.

Station Auxiliary Power Supply

This device is used to provide power to an electronic phone that is connected more than 300 meters (or 1,000 feet) or so away from the Key Service Unit.

Station Battery

A separate power source which provides the necessary DC power to drive a telephone system. Individual telephones are usually powered by a central source, i.e. their PBX or central office. The batteries may also power radio and telephone equipment as well as provide emergency lighting and controls for equipment. See Battery.

Station Busy Lamps

Lamps located on a station instrument, providing visual indication of each busy phone in the system. Busy Lamp Fields (BLFs) often come on key systems and sometimes on smaller PBXs. They're very handy.

Station Busy Override

Pre selected phones have the privilege and ability to preempt busy circuits and override a private conversation.

Station Call Transfer

A phone user can transfer incoming and outgoing calls to another phone without attendant assistance.

Station Camp-On

Phones can camp-on to a busy extension. The camped-on phone will be notified of the camp-on by a special beep signal. The person at the other end may or may not hear the signal.

Station Clock

The principal clock or alternative clock located at a particular station providing the timing reference for all major telecommunications functions at that station. A station clock may also be used to provide timing or frequency signals to other equipment.

Station Code

The final four digits of a standard seven or 10 digit telephone number.

Station Conductor

A wire that terminates at the equipment side of the lightning protector.

Station Direct Station Selection

The phone user places a call to an extension within the PBX by pushing a single pushbutton on his phone.

Station Equipment

Telephone instruments and associated equipment furnished to subscribers. We suspect that the word "station" came from early telephone industry which was regulated by the same government agency which regulated the railroad business.

Station Hunting

This feature allows a calling phone which places a call to a busy phone to proceed to the next idle phone in the hunt group. This jump is done automatically. See also Rotary Hunt, which is the same thing for trunks.

Station Keeping

The process on board a satellite for keeping it at its assigned longitude and inclination.

Station Line Cards

Station line cards sit inside telephone systems and drive a bunch of connected phones. These cards translate the software inside the phone system into electrical impulses which tell the phones at the other end what they're capable of and let them do things, like dial, transfer, conference, etc.

Station Line Protector

Circuitry that protects the telephone system from high voltage hits and lightning strikes. Such circuitry is usually on every station line card.

Station Load

The total power requirements of the integrated station facilities.

Station Message Detail Recording

Now refers to the RS-232-C "port" or plug found on the back of most modern PBXs and some larger key systems. See Call Accounting System and Call Detail Recording.

Station Message Registers

Message unit information centrally recorded on a per-station basis for each completed outgoing call.

Station Message Waiting

Special light on a phone to alert hotel/motel guests of messages waiting at the front desk.

Station Monitoring

Selected phones can monitor (i.e. listen in on) any other phones in the system.

Station Override Security

Designated phones can be shielded against executive busy override (presumably other executives).

Station Protector

A station protector protects phones and other phone-like devices ("stations") from lightning. A station protector is typically a gas discharge, carbon block or other device that short circuits harmful voltages to ground in the event of lightning strikes on the phone line. Sometimes it works. Sometimes it doesn't. If a bad thunderstorm is about to erupt over your house or office, it's a good idea to unplug your phones from AC and from phone lines.

Station Rearrangement And Change

Allows a user to move phones, change the features and/or restrictions assigned to phones and administer features associated with telephones.

Station Review

A study of how people in an organization use the telephones and what communications needs are not being satisfied.

Station Ringer Cutoff

Allows the ringer on the telephone to be turned off. Not always a good idea, since calls may still come in for that phone, but no one may pick them up because they don't hear it ring.

Station Set

Another word for a common desk telephone. Station comes from earliest days when the phone industry in the U.S. was regulated by the same agency that regulated the railroads. It made phones stations, thus easier for the government bureaucrats.

Station To Station Call

A directly dialed call. No operator is used. Most calls are now directly dialed . Some long distance companies don't even have operators to help complete calls. AT&T still does.

Station Tone Ringing

Electronic tone ringer that replaces the bell.

Station Transfer Security

If trunk call is transferred from one phone to another, and the second phone does not answer within a predetermined time, the trunk call will automatically go to the attendant.

Station Visual Signaling

Lamp on a phone which indicates flashing incoming, steady busy, and "wink" hold visual conditions associated with that phone.

Station Wire

SW. The twisted-pair copper telephone wire used to connect stations (i.e., terminal equipment) to PBXs. Also, the telephone wire used inside the residence to connect telephone sets and computer modems to the NIU (Network Interface Unit) that provides the interface to the local loop that connects your house to the telephone company's CO (Central Office).

Stationary Orbit

An orbit, any point on which has a period equal to the average rotational period of the Earth, is called a synchronous orbit. If the orbit is also circular and equatorial , it is called a stationary or geostationary orbit.

Statistical Equilibrium

A telephone company definition. A state of traffic in which, over any considerable length of time, the call arrivals and departures are essentially equal. Traffic that is in statistical equilibrium has an average value of some measure of its level (such as the number of attempts arriving in a specified time interval) that does not change with time.

Statistical Multiplexing

A multiplexing technique that differs from simple multiplexing in that the share of the available transmission bandwidth allocated to a given user varies dynamically. In other words, in statistical multiplexing, a channel is assigned only to devices (e.g., telephone, data terminal or fax machine) which are active and seeking to communicate. Static multiplexers, the original multiplexers, dedicated a channel to a device whether it was active or not. This was horribly wasteful , as devices commonly are inactive. As a result, statistical multiplexing is much more powerful than normal static FDM (Frequency Division Multiplexing) or static TDM (Time Division Multiplexing). In other words, Statistical Multiplexers act as contention devices, as well as multiplexers, making intelligent decisions about providing access to expensive bandwidth based on programmable parameters such as first-come-first- served , application priority (e.g., data vs. voice), and bandwidth reservations . See also Fast Packet Multiplexing, FDM and TDM.

Statistical Process Control

The mathematics of quality control in manufacturing.


74.3% of statistics are made up on the spot. People will accept made-up statistics if:

  1. They seem plausible. You couldn't say that 67% of people are women. It's not plausible. But 50.13% is. Simple statistics, like 75% of... are generally not believable. But 75.1% is, and

  2. No one has any better statistics to contradict you.

  3. If they want to believe because it suits their ends, or most importantly, if they can use your statistic to justify something they want to do.

  4. If your statistics are repeated often enough and in many diverse places by many diverse sources.

Some wags also define statistics as numbers looking for an argument. My favorite statistic is that, on average, everyone has one testicle.

Statistics Port

In network management systems, interface for reporting events and status.


A statistical multiplexer. See Statistical Multiplexing.

Status Information

Information about the logical state of a piece of equipment.

Status Signal Unit

Signal unit of CCS used to initiate transmission on a link or to recover from loss of transmission.

Statute Mile

A unit of distance equal to 1.609 km, 0.869 nmi, or 5,280 ft.

Stay or Bail Moment

The precious few seconds that elapse after loading the front page of a Web site, during which one decides to either stay or leave. Defined by David Siegel in his book "Creating Killer Web Sites."


See Set Top Box.


  1. Society of Telecommunications Consultants. A professional society for telecommunications consultants. They endeavor to set standards of behavior for the consulting community, chiefly to avoid having telecom consultants recommend to their clients equipment they receive a secret commission on from the manufacturer.

  2. System Time Clock: The master clock in an MPEG-2 encoder or decoder system.


Subscriber Trunk Dialing. An non-North American term for direct distance dialing, i.e. dialing long distance calls directly without an operator's assistance. Pricing for long distance calls is typically done by billing a standard amount of money, e.g. a German Mark, for a length of speaking time, which shortens the further you call. For example. you might get one minute for a Mark if you're calling 50 miles. If you call 200 miles you might only get 20 seconds.


Statistical Time Division Multiplexer. STDMs are TDMs (Time Division Multiplexers) with an added microprocessor that provides more intelligent data flow control and enhanced functionality, such as error control and more sophisticated user diagnostics. The major difference between TDMs and STDMs is that stat muxes dynamically allocate time slots on the link to inputting devices on an as-needed basis (rather than in round- robin fashion where all devices are polled in preordained order). Therefore, there is no idle time on the link because a device does not have information to send. Unlike TDMs, STDMs have buffers for holding data from attached devices. They can handle a combined input speed (aggregate speed) that exceeds the speed of the communications link.


  1. Station Terminal Equipment.

  2. Section Terminating Equipment. SONET equipment that terminates a section of a link between a transmitter and repeater, repeater and repeater, or repeater and receiver. This is usually implemented in wide area facilities and not implemented by SONET Lite. STE Network elements perform section functions such as facility performance monitoring. The section is the portion of a transmission facility between a lightwave terminal and a line repeater or between two line repeaters.

  3. Spanning Tree Explorer: A Source Route Bridging frame which uses the Spanning Tree algorithm in determining a route through a network. Often used in ATM networks.

Steady-state Condition

  1. In a communication circuit, a condition in which some specified characteristic of a condition, such as value, rate, periodicity, or amplitude, exhibits only negligible change over an arbitrarily long period of time.

  2. In an electrical circuit, a condition, occurring after all initial transients or fluctuating conditions have damped out, in which currents, voltages, or fields remain essentially constant or oscillate uniformly without changes in characteristics such as amplitude, frequency, or wave shape.

  3. In fiber optics, synonym for equilibrium mode power distribution.

Stealth Tower

A wireless communications antenna disguised as part of the natural or urban landscape. The antennae can appear as a flagpole , a group of rocks, a church steeple, a cactus or large tree. According to Wired news there were about 130,000 communications antennae in place across the United States in 2002, of which roughly 75 percent were standard antennae and the rest "surreptitiously stashed in scenic simulations." Many stealth towers give amusement a whole new meaning. Stealth is also a trade name for a company that makes this type of site.

Steel and electricity revolution,

The steel and electricity revolution took place from about 1875 to 1920 in the United States and Germany. It was an age of massive engineering and the electrification of the economy.

Steerable Beam Antenna

An antenna whose main beam can be directed in various directions either by an electrical or mechanical drive system.


Steganography, also known as "stego," translates from Greek as "covered writing," is a method of hiding one piece of information within another. The ancient Greek historian Herodotus described how a countryman sent a secret message warning of an invasion by carving it into the wood underneath a wax tablet. Slaves would sometimes have their heads shaved and secret messages tattooed on their scalps. After their hair grew back, they would be sent on missions. When they ultimately reached their destinations, their heads would be shaved and the messages read. Contemporary stego is the practice of encoding hidden messages into the least significant bit of other files, such as graphic, audio and HTML files, which have lots of unused space. Inexpensive, commercially available software programs are available which allow you and me to create stego files and include our very own messages. Some even allow messages to be hidden in the whitespace at the end of a line of a text file or e-mail message. Once the data is encoded, it can be decoded only with the proper password. The terrorist Osama bin Laden allegedly uses stego files to transmit maps, photos and instructions outlining future targets via pornographic bulletin boards and sports chat rooms. If the stego message is encrypted, it may be virtually impossible to decode it, assuming that it can be found. Steganography is used to watermark copyrighted digital material. See also Encryption and Watermark.


See Steganopraphy.

Stella Awards

The Stella Awards are named after 81-year-old Stella Liebeck who spilled coffee on herself and successfully sued McDonalds. That case inspired the Stella awards for the most frivolous successful lawsuits in the United States. Among recent candidates:

  • Kathleen Robertson of Austin, Texas, was awarded $780,000 by a jury of her peers after breaking her ankle tripping over a toddler who was running inside a furniture store. The owners of the store were understandably surprised at the verdict, considering the misbehaving little toddler was Ms.Robertson's son.

  • Terrence Dickson of Bristol, PA, was leaving a house he had just finished robbing by way of the garage. He was not able to get the garage door to go up since the automatic door opener was malfunctioning. He couldn't re-enter the house because the door connecting the house and garage locked when he pulled it shut. The family was on vacation and Mr.Dickson found himself locked in the garage for eight days. He subsisted on a case of Pepsi he found and a large bag of dry dog food. He sued the homeowner 's insurance claiming the situation caused him undue mental anguish. The jury agreed to the tune of $500,000.

  • Mr. Merv Grazinski of Oklahoma bought a brand new 32- foot Winnebago motor home. On his first trip home, having driven onto the freeway, he set the cruise control at 70 mph and calmly left the drivers seat to go into the back and make himself a cup of coffee. Not surprisingly, the RV left the freeway , crashed and overturned. Mr. Grazinski sued Winnebago for not advising him in the owner's manual that he couldn't actually do this. The jury awarded him $1,750,000 plus a new motor home. The company actually changed their manuals on the basis of this suit, just in case there were any other complete morons buying recreation vehicles.


Stentor was formed in 1992 as the long distance network of nine regional Canadian phone companies. Inspiration for the name came from the Greek poet Homer. He had immortalized Stentor, a warrior in the Trojan war, "whose voice was as powerful as the voices of 50 other men." And so the adjective "stentorian" survived to be applied to someone with a powerful voice, often a politician. The nine original members of Stentor are Bell Canada, British Columbia Telephone (BC Tel), AGT Limited, Manitoba Telephone Systems, SaskTel, Maritime Telephone, New Brunswick Telephone, Island Telephone and Newfoundland Telephone. On January 1, 1999, Stentor got changed. The members said they would concentrate their co- operative efforts in an enhanced Stentor Canadian Network Management (SCNM). to ensure continuity and seamless service for customers. Members of the alliance are now Bell Canada, British Columbia Telephone (also called BC TEL), Island Tel, Manitoba Telecom Services Inc., Maritime Tel & Tel, New Brunswick Telephone (also called NBTel), NewTel Communications, NorthwesTel, Qu bec T l phone, SaskTel and TELUS.


  1. One movement of an electromechanical switch which typically corresponds to one impulse from a rotary dial or one impulse from a touch tone phone which has been converted to a rotary dial. See also SxS.

  2. An abrupt change in the refractive index between the core and the cladding in a optical fiber. See also Refractive Index and Step-Index Fiber.

Step By Step

SXS. An automatic dial-telephone system in which calls go through the switching equipment by a succession of electromechanical switches that move a step at a time, from stage to stage, each step being made in response to the dialing of a number. SXS is electromechanical switching. It was invented in the 1920s. See SxS.

Step Call

The phone user can, upon finding that the called phone is busy, call an idle nearby phone by merely dialing an additional digit.

Step Down

  1. To reduce the voltage. Such reduction in voltage will increase the current.

  2. A feature of fax machines that makes them drop their transmission speed when the quality of the phone lines they are transmitting over begins to deteriorate. Dropping the transmission speed is the major way of getting the faxes through on "dirty" lines. All Group III fax machines have "step-down" as a built in feature, or should have.

Step Down Transformer

A transformer wound to give a lower voltage on the secondary side than that impressed on (i.e. put into) the primary. The current, however, will be stepped up. A step down (often spelled step-down or stepdown) transformer has more primary than secondary turns. See also Stepdown Transformer and Joint Pole.

Step Index Fiber

A type of MultiMode Fiber (MMF) marked by an abrupt change, or step, in the refractive index between the core and the cladding. Errant portions of light- waves that enter the cladding pick up speed due to the difference in the refractive index of the cladding, which is due to its much clearer (fewer impurities) nature. This allows those errant portions of the lightwaves to catch up with those portions that traveled more or less through the center, or core, of the fiber, and which, thereby, traveled more slowly. Step- index fiber overcomes the effects of modal dispersion. See also Graded-Index Fiber, Modal Dispersion, Multimode Fiber and Refractive Index.

Step Index Profile

For an optical fiber, a refractive index profile characterized by a uniform refractive index within the core and a sharp decrease in refractive index at the core-cladding interface. See also Step Index Fiber.

Step Up Transformer

A transformer wound to give a higher voltage on the secondary side than that impressed on the primary. The current, however, will be stepped down. It has fewer primary than secondary turns.


See Step by Step.

Stepdown transformer

An oil-cooled transformer often mounted a telephone pole. Such transformer converts the primary voltage to the secondary voltage. Most step- down transformers are designed for single-phase operation; if a three-phase secondary circuit is required, three physical transformers are sometimes mounted on the same pole. See Joint Pole.

Stepped Index

Referring to a type of optical fiber which exhibits a uniform refractive index at the core and a sharp decrease in the refractive index at the core-cladding interface.

Stereophonic Crosstalk

An undesired signal occurring in the main channel from modulation of the stereophonic channel or that occurring in the stereophonic channel from modulation of the main channel.

Stereophonic Sound Subcarrier

A subcarrier within the FM broadcast baseband used for transmitting signals for stereophonic sound reception of the main broadcast program service.

Stereophonic Sound Subchannel

The band of frequencies from 23 kHz to 99 kHz containing sound subcarriers and their associated sidebands.


In German, he means to tailor and that he does with great attention to detail and fine craftsmanship. A more talented man you couldn't hope to meet.


An entity that is responsible for maintaining the authoritative copy of a set of corporate data, as well as ensuring the semantic integrity of that set of data.


An imaging term. Scale To Gray. STG uses gray pixels to fill in jagged edges of document images. STG improves readability. According to a study commissioner by Cornerstone and done by Dr. Jim Sheedy, the ability to read STG images was improved between 4% and 19%, depending on the resolution, and symptoms such as headaches , tired back, blurred vision were cut way down.


Standard Time and Frequency Signal.


Pronounced sticky. It stands for Self Teaching Interpretive Communicating Interface. It's being touted as the "next wave of user interface" (the next wave after GUI). According to BIS Strategic Decisions, features of STICI include:

Self-Teaching: The operating system (OS) and interface use agents (special background processes) to study how the user makes use of the device. For example, agents will track exactly how a user use the OS and applications.

Interpretive: The system is able to make inferences based on the information it has collected about the user. The system does some interpretation, moving from the traditional interface approach of "Do what I say" to "Do what I mean." Unlike the static menus and dialog boxes of GUI systems, STICI systems will dynamically adapt their operation, thereby better anticipating user needs. Agents will automate common tasks , based on observed usage patterns.

Communicating: The system will be able to manage all the different communications functions offered , such as store and forward, cellular, logging on and off wireless LANs and linking to the user's desktop PC. These communications will be transparent to the user, leaving him or her free to concentrate on the task at hand.

Interface: The interface will be oriented around documents. Traditionally, interfaces have centered on applications, such as a word processor or a spreadsheet. With the STICI, the interface is centered on documents. The user creates a document, writing or drawing freely , and the various applications needed are simply tools accessed to create a chart, to write or to show numbers within that document. Users will be able to seamlessly link applications from multiple vendors , as descendent technologies evolve from OLE and Publish & Subscribe. Both Microsoft and Apple are developing document-oriented interfaces for the next generations of their respective desktop operating systems.


The New York Times calls it "the marketing buzzword of the moment." A sticky Web site keeps users glued to it, according to the Times, "either through sheer intrinsic niftiness or by piling layer upon layer of more or less related offerings, like stock quotes, weather updates or interactive whiz-bangs like sports trivia."


  1. A sticky shift key lets you access the shifted functions (such as capital A) by pressing the shift key first and then pressing the second key. Sticky keys may stay down for a second or two. Or you may have to hit them again to unstick them ” somewhat like the CapsLock key.

  2. An adjective applied to a web site or a service where visitors hang around. For instance, a banking site that offers a financial calculator is stickier than one that does not because visitors do not have to leave to find a resource they need. When AT&T Wireless introduced voice portals to its customers one of its executives said, "When you provide a service like this it makes your relationship with customers more sticky." In other words, customers are more likely to stick with companies that offer services they like. You restrain your chuckle. See also Stickiness.

Sticky Note

See Post-it Note.


Service Termination Identifier. An ISDN Service Profile term.

Stimulated Emission

Radiation emitted when the internal energy of a quantum mechanical system drops from an excited level to a lower level when induced by the presence of radiant energy at the same frequency. An example is the radiation from an injection laser diode above lasing threshold.


  1. Standard Telegraph Level.

  2. Studio-To-Transmitter link ” typically through the air microwave.


Synchronous Transfer Mode. A transport and switching method that depends on information occurring in regular and fixed patterns with respect to a reference such as a frame pattern. A time division multiplex -and-switching technique to be used across the user's network interface for a broadband ISDN. It gives each user up to 50 million bits per second simultaneously ” regardless of the number of users. See also ATM.


Synchronous Transport Module 1: SDH standard for transmission over OC-3 optical fiber at 155.52 Mbps.


Synchronous Transport Module "n": (where n is an integer) SDH standards for transmission over optical fiber (OC-'n x 3) by multiplexing "n" STM-1 frames, (e.g., STM- 4 at 622.08 Mbps and STM-16 at 2.488 Gbps). The SONET version is known as STS (Synchronous Transport Signal), beginning at 51.84 Mbps.


Synchronous Transport Module "n" concatenated : (where n is an integer) SDH standards for transmission over optical fiber (OC-'n x 3) by multiplexing "n" STM-1 frames, (e.g., STM-4 at 622.08 Mbps and STM-16 at 2.488 Gbps, but treating the information fields as a single concatenated payload).


  1. Statens Telenamd (Swedish National Telecommunications Council).

  2. Super Twist Nematic is the least expensive and most basic form of passive-matrix LCD display. It is used in low cost laptop computers. In a passive matrix color screen, like STN, the current travels along transparent electrodes printed on the glass screen. These electrodes are driven by transistors placed around the edges of the display. Horizontal and vertical electrodes form a grid-like matrix, with a pixel at every intersection. A major problem with passive technology arises when current is lost in crosstalk as the electrodes crisscross each other. This crossing over effect greatly diminishes overall display quality. See Active Matrix, LCD and TFT.


Someone whose services make you broker. See also Small Fortune.

Stop Band

A spectrum of frequencies blocked by an electronic (filter) device and usually defined by upper and lower -3 dB points.

Stop Bit

The Stop Bit is an interval at the end of each Asynchronous Character that allows the receiving computer to pause before the start of the next character. The Stop Bit is always a 1. See Start Bit.

Stop Element

The last element of a character in asynchronous serial transmission, used to ensure recognition of the next start element.

Stop Order

An order that becomes a market order to buy (buy stop) or a market order to sell (sell stop) only when the security trades at a specific price, known as the stop price. A buy stop order is placed above a stock's current market price and is executed if the market rises to, or through, that price. A sell stop order is placed below a stock's current market price, and is executed if the market falls to, or through, that price.

Stop Record Signal

In facsimile systems, a signal used for stopping the process of converting the electrical signal to an image on the record sheet.

Stop/Start Transmission

A method of transmission in which a group of bits are preceded by a start bit and followed by a stop bit. Also called asynchronous transmission. See Asynchronous.

Storage Area Network

See SAN.

Storage Blade

See Blade Server.

Storage Bytes

I made this term up because of the need to explain that one million bytes can be different to one million bytes. OK. Normally, one million means 1,000,000. And it does, except inside a computer, where they measure storage in bytes. Your hard disk contains this many bytes, let's say eight gigabytes. That's fine. But they're not bytes the way we think of them in internal or external computer transmission terms. They're different and they have to do with a way computer stores material ” on hard disks or in RAM. They're what I call "storage bytes." When we talk 1 Kb of storage bytes, we really mean 1,024 bytes. Which comes from the way storage is actually handled inside a computer, and calculated thus: two raised to the power of ten, thus 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 = 1,024. Ditto for one million, two raised to the power of twenty, thus 1,048,576 bytes. See also the introduction to this dictionary and BPs.

Storage Unit

A device in which information can be recorded and retained for later retrieval and use.

Storage Virtualization

In its purest form, according to InfoWorld, virtualization allows users to add storage capacity using inexpensive commodity disk and tape drives to dynamically manage those storage resources as virtual storage pools with little regard for what physically resides on the back end. InfoWorld lists the advantages of storage virtualization as follows :

  1. Virtual pools of storage. Replacing the direct links between host servers and physical disks with logical volumes makes storage a plastic container that can be shared among hosts and applications.

  2. Speedy Recovery. The use of logical volumes simplifies the creation of backups for quick recovery from failures or disasters and snapshots of disk images that can be used with offline applications such as data warehousing tools.

  3. Huge Containers. Combining the capacities of multiple physical drives into one large logical volume simplifies the allocation of storage for very large databases.

  4. Power in numbers. Data can be distributed across multiple physical devices not only to create redundant copies and reduce the impact of media failure, but also to boost the speed of data storage and retrieval.

  5. Unwasted space. Because data in the storage pool can be distributed to physical devices throughout the storage network, storage is used more efficiently - and available space isn't wasted .

Store And Forward

S/F. In communications systems, when a message is transmitted to some intermediate relay point and stored temporarily. Later the message is sent the rest of the way. Not very convenient for voice conversations, but useful for telex type, and other one-way transmission of messages. Telephone answering machines, as well as voice mailboxes are considered forms of Store and Forward message switching.

Store Locator Service

See Single Number Dialing.

Stored Procedures

Compiled code on a database server that reduces the processing burden on clients.

Stored Program

A telephone company definition. The instructions which are placed in the memory of common controlled switching unit and to which it refers while processing a call. Stored programs commonly use alterable magnetic marks to record the program instruction. See also Stored Program Computer and Stored Program Control.

Stored Program Computer

A computer controlled by internally stored instructions, that can synthesize and store instructions, and that can subsequently execute those instructions. See also Stored Program Control.

Stored Program Control

SPC. The routing of a phone call through a switching matrix is handled by a program stored in a computer-like device, which may well be a special-purpose computer. Before SPC switches came along, the rotary dialing of the phone caused the elements of the switch to directly "step" through their dialing path. This was slow and cumbersome, since dialing can be slow. Also subscribers can abort half way (they made a mistake) and this can mess up the switch's efficiency. Thus the move to stored program control switches was very significant. These days virtually all switches as stored program control. Nothing happens in the switching matrix until the stored program control receives all the dialing digits and decides what to do with them.


A word made up by guru George Gilder. He


His mother should have thrown him away and kept the stork ” Mae West.


In a call center, agents typically need access to many databases. In the past they've used dumb terminals. They log into one computer, get into one database, go further into it. When they need information out of another database, they've typically had to climb out of the previous database, the previous computer, log into another and climb down into it. This is called stovepiping, because it follows the contours of a stovepipe. These days, agents have intelligent computers as terminals. They can access several databases at once, by simply having different windows open on their screen or having a front end program that populates a screen with information from several databases, most likely using a GUI interface.


  1. Shielded Twisted Pair. Twisted pair (TP) wiring with a metallic shield surrounding the signal-carrying conductors in order to protect them from ambient noise in the form of EMI (ElectroMagnetic Interference). The outer shield may be in the form of a thin metallic mesh in the case of ScTP (Screened Twisted Pair). Alternatively, it may be in the form of a very thin metallic foil in the case of FTP (Foil Twisted Pair), which also is known as SSTP (Double-Shielded Twisted Pair, as in Shielded-Shielded Twisted Pair). In either case, the shield effectively serves to ensure noise-free information transfer. The shield, however, acts as an antenna, converting received noise into current flowing in the shield; it must be properly electrically grounded with a drain wire, or the shield current actually will intensify the noise problem. Any discontinuity in the shield also will result in increased noise. To function effectively, every component of a shielded cabling system must be fully shielded, and the continuity of the shield must be maintained across cable splices. See also Attenuation and STP-A.

  2. Signal Transfer Point. The packet switch in the nation's emerging Common Channel Interoffice Signaling (CCIS) system. The CCIS is a packet switched network operating at 4800 bits per second. CCIS replaces both SF (Single Frequency) and MF (Multi-frequency) by converting dialed digits to data messages. It will run at 56,000 bps with the introduction of Signaling System 7. See Signaling System 7. For a full explanation of the Advanced Intelligent Network, see AIN.

  3. Spanning Tree Protocol. See Bridge.


Shielded Twisted Pair-A. A modification of the original STP standard, STP-A supports increased carrier frequencies and, therefore, increased transmission speeds. STP-A makes use of the same cable, although the improved connector includes a metal shield between the two conductors as a crosstalk barrier . The new connector mates with the old. STP-A originally was tested up to 100 MHz, and now up to 300 MHz, in support of high- speed Token Ring. See also STP.


When wiring up phone and some data extensions, there are basically two ways of doing it ” straight-through and crossover. Straight-through occurs when you wire both ends identically so the signals pass directly straight through. Crossover wiring has a reverse order of wiring. As an example, let's take a four conductor, RJ-11. In a crossover wiring (e.g. an RJ-11 two wire phone extension cord), conductor 1 on one plug would be connected to position 1 on one plug and position 4 on the other end. Conductor 2 would be connected to 3. And 3 would be connected to hole 2.

Straight-Tip Connector

ST Connector. An optical fiber connector used to join single fibers together at interconnects or to connect them to optical cross connects. See also FC Connector, SC Connector, and SFF Connector.

Straightforward Outward Completion

Operator can place an outgoing call for phone user. Also called "Through Supervision."

Strain Relief

The connection between the cable and the termination, usually a modular plug, that bonds the cable jacket to the connector so that the individual conductors don't have to absorb tension when the cable is pulled or moved. There are two types of strain relief. The primary strain relief crimps onto the cable's outer jacket where the modular plug meets the cable, and the secondary strain relief crimps onto the rubbery insulation around each conductor inside the business end of the plug. Not all crimp dies crimp the secondary strain relief, and some crimps have a different secondary strain relief location. If the cable jacket and conductors' insulation isn't crimped, the strain of moving or pulling the cable (this is especially important at the desktop, where cables get unplugged and plugged, jostled and pulled) is all borne by your copper connection. Make sure the modular connectors (cable plugs) your technician is crimping have primary and secondary strain relief. Some dies for crimping tools don't support secondary strain relief, which anchors the insulation around the cable conductors to the plug. Strain relief is important because otherwise the fragile copper wire carrying your connection takes all of the tugging and pulling when the cable is plugged in and unplugged or moved. If the sheath of the cable is not attached to the modular plug at, (this is called primary strain relief), your connections has no strain relief at all. The cable sheath should be anchored at the end of the plug away from the connectors. Bye-bye connection.

Strained Silicon

Strained silicon is the method developed by IBM of stretching silicon over a silicon germanium substrate layer to improve the speed of semiconductor processing.


  1. A single uninsulated wire.

  2. Strand (as the term applies to telephone companies) is an uninsulated and unpowered stranded steel cable, installed on telephone and utility poles and similar structures to support telephone cable. Cable is lashed to the strand; other devices are fitted with clamps which attach to the strand. On joint poles, the CATV strand is usually installed below electric power facilities and above the telephone facilities.

  3. Strand (as the term applies to cable television) is an uninsulated and unpowered stranded steel cable, typically 1/4" or 3/8" diameter, installed on telephone and utility poles and similar structures to support cable television distribution devices such as hard cable, amplifiers and taps. Cable is lashed to the strand; other devices are fitted with clamps which attach to the strand. On joint poles, the CATV strand is usually installed below electric power facilities and above telephone facilities. See Hard Cable, Joint Pole, and Lashing.

Strand Lay

The distance of advance of one strand of a spirally stranded conductor, in one turn, measured axially.

Stranded Conductor

A conductor composed of groups of wires twisted together.

Stranded Copper

A type of electrical wire conductor comprised of multiple copper wires twisted together forming a single conductor and then covered with an insulating jacket. Stranded conductors perform less well than do solid-core conductors in terms of transmission quality, and are more distance-limited. Stranded conductors have greater flex strength, however; therefore, they are commonly used in applications where the cable is flexed frequently and aggressively.

Stranded Fiber Cable

A fiber optic cable in which multiple individual optical fibers contained within the same cable sheath are twisted around each other in a helix . Also twisted with the fibers are strength members, generally constructed of aramid (commonly known as Kevlar). The twisting process improves the flex strength of the cable, much as is the case with stranded copper. If the fibers were not helically stranded, each fiber essentially would stand on its own, and would be more susceptible to fatigue, which would result in the growth of surface imperfections or microcracks, and eventually fiber breakage . See also Aramid, Helix and Stranded Copper.


A permanent, wired connection between two more points. Older style data modems did some of the feature selection using DIP switches. They called that "straps." Even today, some software option commands have become called "software straps."


The act of installing a permanent connection between a Point of Termination (POT) Bay and a collocated party's physical collocation node.

Strategic Alliance

When a company does something with another company, both companies will announce they now have a "strategic alliance." Such strategic alliance may be anything from one company agreeing to include the other company's products in its lineup (often without a commitment to actually sell anything). Or it may simply be that each have agreed to include a hyperlink to each other on each other's web sites. In short, I've never figured what a strategic alliance really is or what its benefits are ” other than an attempt to boost each other's stock by issuing more press releases to the financial community.

On August 10, 2000, the Wall Street Journal reported : SEATTLE ” Inc. announced a strategic alliance with Inc. to create a co-branded toy and video- games store. The deal could create a toy giant., combining the online unit of Toys "R" Us Inc., Montvale, N.J., with the Internet's largest retailer. Both Amazon and are already leading sellers of toys online, but face a raft of competitors including eToys Inc. Under the terms of the 10-year agreement, Amazon will receive a combination of periodic fixed payments, per-unit payments and single-digit percentage of revenue. The level of the payments weren't disclosed. Amazon will also receive warrants entitling it to acquire 5% of You can figure what "strategic alliance" really means. See also Strategic Partnership.

Strategic Investor

One who can deliver customers, managements contacts, and other help in addition to money.

Strategic Partnership

A fancier term for strategic alliance. See Strategic Alliance for just how vague a definition can get.

Stratum Level

In any digital network, you need a clock ” a source of timing to let transmissions know where they begin and where they end. But in any network, there are "levels" of clocks. Think of the clocks you have at home. (This analogy is stretching it. But it's a good beginning.) Somewhere at home you have your "main clock" ” the one you consider to be most accurate. For me it's my digital wristwatch. When I compared my wristwatch against my computer, my wristwatch said it was two minutes later. So I called an operator at the local phone company. She gave me a different time, but she assured me that her timing was accurate, since it was on her console and derived from a distant , accurate network clock. So let's say that that's my main source of timing. That would be my level 1 timing. From there, I transfer it to my PC, my watch, etc. which would be my level two timing.

Now let's move to the digital network. An American National Standards Institute (ANSI) standard entitled "Synchronization Interface Standards for Digital Networks" (ANSI/T1.101-1987) was released in 1987. This document defines the stratum levels and minimum performance requirements. Stratum 1 is defined as a completely autonomous source of timing which has no other input, other than perhaps a yearly calibration. The usual source of Stratum 1 timing is an atomic standard or reference oscillator. The minimum adjustable range and maximum drift is defined as a fractional frequency offset delta f/f of 1 x ten raised to the minus eleven or less. At this minimum accuracy, a properly calibrated source will provide bit-stream timing that will not slip relative to an absolute or perfect standard more than once every four to five months. Atomic standards, such as cesium clocks, have far better performance. A Stratum 1 clock is an example of a Primary Reference Source (PRS) as defined in ANSI/T1.101. A PRS source can be a clock system employing direct control from Coordinated Universal Time (UTC) frequency and time services, such as Global Positioning System (GPS) navigational systems. The GPS System may be used to provide high accuracy, low cost timing of Stratum 1 quality.

A Stratum 2 clock system tracks an input under normal operating conditions, and holds to the last best estimate of the input reference frequency during impaired operating conditions. A Stratum 2 clock system requires a minimum adjustment (tracking) range of 1.6 x 10 raised to the minus eight. The drift of a Stratum 2 with no input reference is less than 1.6 x 10 raised to the minus eight in one year. Stratum 3 is defined as a clock system which tracks an input as in Stratum 2, but over a wider range. A Stratum 3 clock system requires a minimum adjustment (tracking) range of 4.6 x 10 raised to the minus six. The short term drift of the system is less than 3.7 x 10 raised to the minus even in 24 hours. This is about 255 frame slips in 24 hours while the system is holding. Some Stratum 3 clock equipment is not adequate to time SONET network elements.

Stratum 3E is a new standard created as a result of SONET equipment requirements. Stratum 3E tracks input signals within 7.1 Hz of 1.544 MHz from a Stratum 3 or better source. The drift with no input reference is less than 1 x 10 raised to the minus eight in 24 hours.

Stratum 4 is defined as a clock system which tracks an input as in Stratum 2 or 3, except that the adjustment and drift range is 3.2 x 10 raised to the minus five. Also, a Stratum 4 clock has no holdover capability and, in the absence of a reference, free runs within the adjustment range limits.

Stratum 4E is a proposed new customer premises clock standard which allows a holdover characteristic that is not free running. This new level, intended for use by customer provided equipment in extending their networks, is not yet standardized. See Network Slip and Timing.

Stray Current

Current through a path other than the intended path. See also Spurious Emission.


This concept is widely used in selling. The simple idea is to set up a Buyer's Checklist and tell your prospective customer that this Checklist is objective. Any product that meets all the criteria is worth buying. Of course, there's only one product that meets all the criteria. It's yours.


  1. A flow of digital information, such as a video stream.

  2. An SCSA term. One of 16 physical data lines making up the SCbus or SCxbus Data Bus. See S.100.


Streaming tape drive.


This is a collective term for people who view or listen to streaming video or audio over the Internet - sources such as online radio stations, webcast films and the like.


An Internet term. A Web page typically consists of text and graphics (still and moving) images. The text is typically fewer bytes than the graphics which are heavy on bytes. Thus, to receive the text to your PC from their Web page typically takes much less time than receiving the graphics images. So Netscape had an idea, which they first pioneered in their browser. Let's get the text up on the user's screen fast, and paint the user's screen with the images as they came in. This allowed the user to look at a new page of text on screen as the graphics came in over the phone lines. Netscape called this streaming. That was the first use of streaming. But then a company called Real Networks came along. It had an idea. Wouldn't it be nice if we could put audio recordings and video (clips, movies, etc.) on a Web site and have people click on them and start hearing or seeing them immediately ” as against (in the pre-Real Networks' days) waiting to download the entire file, then playing it. See Home Page, Internet and Streaming Audio and Streaming Media.

Streaming Audio

see also Internet Radio.

Streaming Content

Let's say you're a very big company with a very big website, for example Microsoft or General Motors. You have people coming to your website from all over the world at all times of the day and night. Clearly if they all home in on your one solitary web site, all sorts of horrible problems are likely to occur. You'll overload the phone lines. You'll overload the computers. You'll overload the routers. You'll overload everything. There's a solution: You go to a company who has made it its business to have servers all over the world connected to the Internet. You copy the content of your web servers to this company's geographically distributed web servers. This way when a customer of Microsoft in Australia wants content from Microsoft in Seattle, that customer does- n't have to contact Seattle, he contacts the local server in Australia. By the way, he does- n't know he's contacting the local server in Australia. He thinks he's contacting Seattle. And he really shouldn't care, since each time, Microsoft's Seattle servers are updated, the geographically distributed servers are also updated. The advantages for the customer are obvious: faster and reliable response. The advantage for Microsoft (or General Motors) is that it gives better service to its customers. The business of providing content from geographically distributed servers is called "streaming content." It is very different to streaming media. See the next definition. And it is very different to plain streaming. See the previous definition.

Streaming Media

Streaming media is basically audio and video (i.e. a movie or a video clip) coming at you in packets over the Internet. The idea of the "stream" and the streaming software necessary to play it is that your audio and your video start playing on your screen before the entire file is downloaded to your machine. Until streaming media came along, you needed the entire audio or video file on your computer intact and in toto before you could play it ” as with today's attachments to email messages. (You need those on your hard disk before you can "play" them back.) If you company starts streaming media to people ” .e.g. for training ” be aware that streaming video can adversely impact the performance of a network. See Streaming.

Streaming Tape Backup

A device to backup files, programs and entire hard disks. A streaming tape backup looks very much like a large audio cassette. It records data sequentially, which means if you want to find specific data, it can take a long time while the tape physically moves backwards and forwards to find the data. Streaming tape backup is best used as backup for an entire computer and best used to restore a computer if all else fails. The problem with streaming tape backup, based on my limited experience, is that it's not very reliable ” largely as a result of it being so mechanical. The tape mechanism breaks down more than it should.

Streaming Tape Drive

A magnetic tape unit especially designed to make a nonstop dump or restore magnetic disks without stopping at interblock gaps.

Streaming Video

See Streaming Media.


An architecture introduced with Unix System V, Release 3.2 that provides for flexible and layered communication path between processes (programs) and device drivers. Many companies market applications and devices that can integrate through Streams protocols.


The StreamWorks Player brings the power of networked audio and video to the desktop. You can play "live" and "on-demand" audio and video from StreamWorks Servers across the globe. The StreamWorks Transmitter allows for LIVE network encoding of digital audio and video over today's networks. Taking inputs from analog audio and video connections, like the ones on the back of a VCR, StreamWorks Transmitter is capable of enabling live, real-time MPEG audio and video over industry standard TCP/IP networks.

Street Price

The real selling price of computers, hardware, and software. Most laptop and desktop computers sell for 25 percent below list price. Software may be discounted even more.

Street Talk

The Banyan-developed protocol for discovering and maintaining resource information distributed among the servers connected to Banyan's VINES network operating system. Also known as a global naming service.


A heavy duty shotgun with a revolving round magazine typically holding 18 12-gauge or 20-gauge shotgun shells . This word crept into a story the Wall Street Journal ran on cellular fraud. When the Feds rang a cellular phone store as a sting operation, one customer offered to trade his streetsweeper in on a phone. That's how dependent Detroit's drug-traffickers had become on cellular phones and beepers.

Strength Member

The part of a fiber optic cable composed of aramid yarn, steel strands, or fiberglass filaments that increase the tensile strength of the cable.

Stress Puppy

A person who thrives on being stressed out.


A sequence of elements of the same type, such as characters, considered as a unit (a whole) by a computer. A data structure composed of a sequence of characters, usually in human-readable text.

Stripe Pitch

The equivalent of dot pitch on aperture grille CRTs; the distance between one stripe and the next one of the same color, expressed in millimeters. See also Resolution.


  1. A term used in data storage technology, such as RAID (Redundant Array of Inexpensive Disks), data striping is the process of dividing a large logical block of data into multiple physical blocks for storage on multiple disk drives. The resulting data partitions residing on multiple disk drives can be combined into a single logical "volume" that the operating system views as a single drive. Data striping offers the advantage of enhanced performance by enabling multiple I/O (Input/Output) operations in the volume to take place in parallel (i.e., simultaneously). Striping is used in the context of Network-Attached Storage (NAS), the most complex implementation of which is a Storage Area Network (SAN). See also NAS, RAID, and SAN.

  2. A Fibre Channel definition. Striping is a way of achieving higher bandwidth using multiple N_ports in parallel to transmit a single information unit across multiple levels.


A signal that triggers a data reading, transfer of information or sampling. Such a sampling might be to figure if a circuit is active and, if so, what level of activity is taking place. The sampling process might allow a carrier to bill the user correctly for circuit usage.


A straight line or arc that is used as a segment of a graphic character.

Stroke Edge

An imaging and OCR term. In character recognition, the line of discontinuity between a side of a stroke and the background, obtained by averaging, over the length of the stroke, the irregularities resulting from the printing and detecting processes.

Stroke Speed

In facsimile systems, the number of times per minute that a fixed line perpendicular to the direction of scanning is crossed in one direction by a scanning or recording spot. In most conventional mechanical systems, this is equivalent to drum speed. In systems in which the picture signal is used while scanning in both directions, the stroke speed is twice the above figure.

Stroke Width

In character recognition, the distance measured perpendicularly to the stroke centerline between the two stroke edges.

Strong text

The HTML character style used for strong emphasis. Certain browsers display this style as bold.

Strowger, Armond

The man who invented the telephone dial and the earliest automatic telephone switch as a method of allowing the user to complete calls without using the Operator. In Kansas City in the late 1800's, Ol' Armond was an undertaker who wasn't getting much business. That's because the girlfriend of a rival undertaker was a telephone operator, and when she got a call asking for the local undertaker, she forwarded the calls to her boyfriend. This story may or may not be apocryphal. But it's a great story.


A system for organizing procedures or equipment. See all the definitions that follow.

Structured Query Language

SQL. A relational database language (ANSI Standard) that consists of a set of facilities for defining, manipulating and controlling data. See SQL.

Structured Programming

A technique for organizing and coding (computer) programs in which a hierarchy of modules is used, each having a single entry and a single exit point, and in which control is passed downward through the structure without unconditional branches to higher levels of the structure. Three types of control flow are used: sequential, test, and iteration.

Structured Wiring

As data flows have sped up in recent years and as moves, adds and changes have proliferated, so the erstwhile idea of wiring up a building with plain old analog voice telephone wire has become no longer intelligent. The idea then came up of defining wiring standards and flexible schemes so that a user could feel comfortable about choosing a complete solution for wiring phones, workstations, PCs, LANS and other communicating devices throughout the building, the campus, the network, the company and throughout his life in the place. Consistency of design, flexible layout and logic are the keys to structured wiring systems. Typically a structured wiring system consists of two elements:

  1. Manufacturer-originated standard components that link wires together in a systematic, intelligent way.

  2. A set of rules for building smart wiring. The ANSI/TIA/EIA-568-A and ISO/IEC 11801 standards specify the minimum requirements for telecommunications cabling within a commercial building. The Commercial Building Telecommunications Wiring Standard is available from Global Engineering Documents, Englewood CO 314-726-0444 / 800-854- 7179.

A structured cabling system will improve performance in five ways, according to Anixter, a leading supplier of structured wiring systems:

  1. It eases network segmentation, the job of dividing the network into pieces to isolate and minimize traffic, and thus congestion.

  2. It ensures that proper physical requirements, such as distance, capacitance , and attenuation are met.

  3. It means adds, moves, and changes are easy to make without expensive and cumbersome rewiring .

  4. It radically eases problem detection and isolation.

  5. It allows for intelligent, easy and computerized tracking and documentation. "Structure" brings order to what has often been an afterthought ” wiring. The main pieces of a structured wiring system are:

  1. Drop cable. The cable that runs from the computer to a network outlet.

  2. Cable run. The cable that runs from the outlet to the wiring closet.

  3. Patch panel. A board that collects all the cable runs in one place and "patches" them to different parts of the wiring concentrator. Network managers (users or their secretaries, it's that simple) change the LAN layout by plugging and unplugging "patch cables" between the patch panel and the wiring concentrators . No rewiring is necessary to move one user from one network segment to another.

  4. Wiring concentrator. It makes the network connections. Some wiring concentrators are dumb, making only physical connections between network segments. Others are intelligent, making networking decisions and providing network diagnostics. A wiring concentrator can have bridges and routers that divide the network into segments. It can have the hardware necessary to change from one media, say twisted pair, to another, say fiber optic. And it can contain the hardware to change from one network type to another, say from Ethernet to Token Ring.

Here is a glossary of structured wiring words, with thanks to Anixter. Access Method The method of "communicating" on the wire. Examples include Ethernet, Token Ring, AppleTalk, AS400 and 3270.

Cable Type (Media) The type of cable used in the system. Examples are coaxial, UTP, STP and fiber. Factors including cost, connectivity and bandwidth are important in determining cable type.

Data Speeds Different interconnect products (cables and connectors) are capable of supporting different data rates. For instance, Level 3 cable supports data rates up to 10 Mbps. (See LEVEL).

Environment Where the structured wiring system is found. The large majority of systems are located in office environments as opposed to factory or industrial environments.

Life Cycle How long the cable is physically anticipated to be in place. For example, if a customer intends to be in a large office for 10 years, fiber installation may be considered.

Methodology The physical means of getting the wiring system to the user (its distribution path). Examples include modular furniture, surface mounts, fixed wall, recessed wall, raised floor and undercarpet wiring.

Topology The way the cable is physically laid out or configured. Examples include star, ring, daisy chain and backbone.

See Smart Home.

Structured Wiring System

See Structured Wiring.


Synchronous Transport Signal. The electrical equivalent of SONET OC-level. The signal begins as electrical and is converted into optical prior to presentation to the fiber optic medium. The STS frame consists of the Synchronous Payload Envelope (SPE), Section Overhead (SOH), Line Overhead (LOH), Path Overhead (POH), and Payload. SOH and LOH comprise what is known as Transport Overhead (TOH). See also STM.


Synchronous Transport Signal level 1. An electrical signal that is converted to or from Sonet's optically based signal; equivalent to the OC-1 signal of 51.84 Mbps.


Synchronous Transport Signal level 2. (yes, that's right. It's STS-3, though it's level 2.) ATM Physical Layer implementation supporting 155 Mbps.


Synchronous Transport Signal "n" : (where n is an integer) SONET standards for transmission over OC-n optical fiber by multiplexing "n" STS-1 frames, (e.g., STS-3 at 155.52 Mbps STS-12 at 622.08 Mbps and STS-48 at 2.488 Gbps).


Synchronous Transport Signal "n" concatenated: (where n is an integer) SONET standards for transmission over OC-n optical fiber by multiplexing "n" STS-1 frames, (e.g., STS-3 at 155.52 Mbps STS-12 at 622.08 Mbps and STS-48 at 2.488 Gbps but treating the information fields as a single concatenated payload).


Secure Telephone Unit.


The third generation of secure telephone units used by the military and its suppliers.

Stub Area

A stub area is an OSPF-defined area of routers which only includes intra- area and inter-area routes in its tables. The ABR (area border router) for that area prevents any externally-originated routes (e.g., RIP, BGP, EIGRP, etc.) that have been redistributed into OSPF from entering the area. The ABR instead sends the area routers a default route so that they may still reach the E1/E2 destinations. A totally stubby area extends this concept further. In addition to blocking external (E1/E2) routes from entering the stub area the ABR also blocks all inter-area routes. In other words the area routers only contain intra- area routes in their tables. Again the ABR provides a default route into the area so that inter-area and external destinations can be reached.

Stub Domain

A local domain in the context of IP networks. A stub domain commonly is a Local Area Network (LAN) which uses IP addressing for local packet data routing. Most of that IP traffic never leaves the local domain for the Internet domain, so it's just a stub, i.e., it goes nowhere. It's analogous to the stub of a finger that you got cut off in a bandsaw. It doesn't go anywhere . It isn't of any use outside of the domain of your hand. You can't even press an elevator button with it. See NAT.

Studio-To-Transmitter Link

STL. Any communication link used for transmission of broadcast material from a studio to the transmitter. It's typically microwave radio but it may also be a conventional landline link.

Study Group 15

The ITU, a United Nations agency, coordinates the development of global communications standards. Study Group 15 of the ITU Telecommunication Standardization Sector (ITU-T) is where the work on communications specifications is carried out. It is responsible for the standards development in the area of transport networks, systems and equipment. See also G.990.

Study Group 16

The ITU, a United Nations agency, coordinates the development of global communications standards. Study Group 16 of the ITU Telecommunication Standardization Sector (ITU-T) is where the work on multimedia communications specifications over the Internet is carried out. See also G.990.

Stunt Box

A device to 1. control the nonprinting functions of a teletypewriter terminal, such as a carriage return and line feed and 2. a device to recognize line control characters.

Stupid Network

See Dumb Network.

Stutter Dial Tone

Stutter Dial Tone is the broken-up tone a user hears on a phone when they pick up their phone to make a call and they have a message waiting in voice mail. This is used to notify users that they have a voice mail message when the phones don't or can't have a message-waiting light. They are given stutter dial tone instead of regular dial tone. See also MWI.


Subscriber (or Subscription) Television.


Start of Text. See Packet.


A pen-shaped instrument (usually made out of plastic) that is used to enter text, draw images, or point to choices on a computer ” desktop or PDA. The pen is designed to make writing on the screen feel just like writing on paper. Yes!


  1. Subscriber Unit. A radio frequency modem used to acquire the airlink. A wireless term.

  2. Service User. The end user at the customer premises.

  3. Signal Unit, a group of bits forming a separately transferable entity used to convey information.


Substitute Character. A control character used in the place of a character that has been found to be invalid or in error.


The band of frequencies between 5 MHz and 45 MHz frequently used as a return path in CATV.


A name for an ISDN service which enables many different types of terminals ” phones, fax machines, PCs, etc. ” to be connected to the ISDN user interface and uniquely identified during a call request. See ISDN.


  1. A carrier which modulates a main carrier so that two different modulating signals can be transmitted simultaneously, one on the main carrier and one on the subcarrier. See Sub Carrier Modulation.

  2. In NTSC or PAL video, a continuous sine wave of extremely accurate frequency which constitutes a portion of the video signal. The subcarrier is phase modulated to carry picture hue information and amplitude modulated to carry color saturation information. The NTSC subcarrier frequency is 3.579545 MHz, and the PAL-I frequency is 4.43361875 MHz. A sample of the subcarrier, called color burst, is included in the video signal during horizontal blanking. Color burst serves as a phase reference against which the modulated subcarrier is compared in order to decode the color information.

Subcarrier Modulation

Subcarrier modulation combines a signal with a single low frequency sine wave. The low frequency signal is called a sub-carrier. This combined signal is then added to a higher frequency radio signal. The resulting high frequency radio signal is very complex and the original signal is not detectable by ordinary means. To detect a signal that has been modulated by a subcarrier, it must be passed through two detector circuits, one to separate the subcarrier from the high frequency radio transmission, and a second to separate the sub-carrier from the desired information.


A teleconferencing term. During the course of a large teleconference, the moderator can hold an off-line subconference (i.e., a caucus, or closed meeting) with a number of participants. During the subconference, the other participants remain connected to the main conference. Once the subconference is completed, that group rejoins the main conference.


Also called a child domain. Normal domains, such as, are called parent domains.


A logical sub-division of a layer.


As defined by the Telecommunications Act of 1996, a subloop is a portion of a local loop that is accessible to terminals at any point in the Incumbent Local Exchange Carrier's (ILEC's) outside plant, including inside wire. An accessible terminal is any point on the loop where technicians can access the wire or fiber within the cable without removing a splice case. Such points can include a telephone pole or pedestal, the minimum point of entry (MPOE), the single point of interconnection, the main distribution frame (MDF), and the feeder/distribution cable interface. Subloops are one of the categories of Unbundled Network Elements (UNEs), which the ILECs must make available to the Competitive LECs (CLECs). See also Local Loop, Telecommunications Act of 1996, and UNE.

Submarine Cable

A cable designed to be laid underwater.


Same as cursor submarining. When you drag your cursor across a screen and the cursor disappears as you move it. That's called cursor submarining. It happens most on monochrome LCD screens because they change slowly ” much slower than active matrix screens or CRTs or VDTs (glass screens).


In X.400 terms, the transmission of a message or probe from an originator's UA (User Agent), MS (Message Store), o AU( Access Unit) to an MTA (Message Transfer Agent).


A small circuit board that mounts on a larger module. Also called a daughterboard.


A subnet is a portion of a network, which may be a physically independent network, which shares a network address with other portions of the network and is distinguished by a subnet number. A subnet is to a network what a network is to the Internet. Here's an explanation. A TCP/IP network can have a lot of traffic flowing across it at any given time. In large networks the flow of information can be too much, causing bottlenecks and congestion that essentially bogs the network down to the point it is ineffective . To alleviate this, a network will be divided into smaller networks called subnets. Subnets are created by configuring the IP addresses for all the computers in the subnet to be similar to each other, but different from other subnets. The different subnets are kept separate by using a subnet mask. A subnet mask filters IP addresses allowing computers with specific IP addresses to talk to each other directly yet other computers will not hear their broadcast traffic. By using subnets, backbones, and routers it is possible for a large network to operate efficiently without any bottlenecks or congestion. See also Subnet Mask.

Subnet Mask

A mechanism that is used to split a network into a number of smaller subnetworks. A subnet mask can be used to reduce the traffic on each subnetwork by confining traffic to only the subnetwork(s) for which it is intended, thereby eliminating issues of associated congestion on other subnetwork(s) and reducing congestion in the network as a whole. A subnet mask also makes the entire network more manageable. In effect, each subnetwork functions as though it were an independent network, keeping local traffic local and forwarding traffic to another subnetwork only if the address of the data is external to the subnetwork. Such decisions are made on the basis of routing tables contained within the various routers, with each routing table comprising an IP (Internet Protocol) address table. (Note that the IP address may be an internal address rather than a registered IP address, with the latter being used only for access to the public Internet. For example, private IP addresses would be used for routing within a LAN, with translation to registered IP addresses taking place if the traffic is intended for the public Internet.) As a data packet is received by a router, an address lookup is accomplished, and the original IP address is translated into a subnet mask address, which also follows the IP address format. The resulting subnet mask address is divided into two parts, a subnetwork address and a host address. The IP address and subnet mask address are compared, and the router decides how to forward the data packet. See Ethernet and Local Area Network.

Subnet Number

A part of the internet address which designates a subnet. It is ignored for the purposes internet routing.


  1. A collection of OSI end systems and intermediate systems under the control of a single administrative domain and utilizing a single network access protocol. Examples: private X.25 networks, collection of bridged LANs.

  2. A token ring LAN that is used to serve the communication needs of a department. Subnetworks are normally connected to token ring backbones via token ring bridges or routers so that they can communicate with other subnetworks via the backbone or with computers directly connected to the backbone.

  3. An ATM term. A collection of managed entities grouped together from a connectivity perspective, according to their ability to transport ATM cells .

Subnetwork Access Protocol

SNAP. A version of the IEEE local area network logical link control frame similar to the more traditional data link level transmission frame that lets you use nonstandard higher-level protocols.


An ATM term. Subnetwork Management System: A Network Management System that is managing one or more subnetworks and that is managed by one or more Network Management Systems.

Subordination of Debt

A debt subordination agreement is a contract in which a junior creditor agrees that its claims against a debtor will not be paid until all senior indebtedness of the debtor is repaid. Under a general subordination agreement, a junior creditor agrees to subordinate its claim to all presently existing and future claims against the debtor. In a specific subordination agreement, a junior creditor subordinates its claim to a particular obligation of the debtor. In recent years, lenders and borrowers have used subordinated debt, such as high yield bonds, institutional subordinated mezzanine financing, participation certificates, and subordinate trust certificates, in an ever-widening variety of transactions, including leveraged buy-outs, securitizations, and real estate financings. Businesses now commonly utilize tiered capital structures consisting of layers of common and preferred stock, management or shareholder debt, mezzanine financing, high yield bonds, and senior bank or asset-based debt. While equity has lost some of its appeal as a currency for acquisition transactions, subordinated debt has gained ground as a cost-efficient financing too.


Less than the standard rate of transmission, which is defined at the voicegrade rate of 64 Kbps. The voice-grade transmission rate is defined at 64 Kbps, as that is the basic building block of the digital transmission hierarchy, based on the original, and most commonly used, PCM (Pulse Code Modulation) standard method for converting analog voice into a digital signal. Therefore, 64 Kbps is the lowest common denominator for digital transmission, across the entire PDH (Pleisiochronous Digital Hierarchy), which includes T-Carrier (North American), E-Carrier (European), and J-Carrier (Japanese). Transmissions at a rate less than 64 Kbps, therefore, are referred to as subrate.

Subrate Switching

Through special equipment and arrangement with the public carrier(s), subrate switching (i.e., switching at less than the standard rate of 64 Kbps) can be accomplished. For example, ISDN can support subrate switching, allowing two or more transmissions to share a 64-Kbps channel over an ISDN local loop. In the carrier network, each of the transmissions is identified, and is switched separately. See also Subrate.


A functionally isolated program or sequence of instructions for a specific function that is often called by a program. A piece of software that performs a useful function that will be needed often. The code for the subroutine is stored on disk (like a letter, etc.) and dropped into a larger program as needed. A nicely -written subroutine saves you "re-inventing the wheel" and allows you to re-use your code in many programs.


A person or company who has telephone service provided by a phone company. In other industries, subscribers are called customers. Some telephone companies are beginning to call their subscribers customers. About time.

Subscriber Access Terminal

SAT. A SMDS term for DTE in the context of a SMDS network. The SAT gains access to the network through either a SNI or DXI interface.

Subscriber Converter

See Set Top Box.

Subscriber Line

The telephone line connecting the local telco central office to the subscriber's telephone instrument or telephone system.

Subscriber Line Charge

SLC. A monthly charge on subscribers created by the Federal Communications Commission and paid to the local telephone company. The logic for this charge has something to do with reimbursing the local phone companies for some costs which they are allegedly not recovering elsewhere. In reality, it's just another rate increase. The SLC also is known variously as the Access Charge, CALC, and EUCL. See also Access Charge.

Subscriber Loop

The circuit that connects the telephone company's central office to the demarcation point on the customer's premises. The circuit is most likely a pair of wires. But it could be three wires if some external signaling is being used. It could also be four wires if the circuit was a four-wire full duplex leased line.

Subscriber Loop Carrier

See SLC-96.

Subscriber Network Interface


Subscriber Number

The number that permits a user to reach a subscriber in the same local network or numbering area (same as Directory Number or DN).

Subscriber Plant Factor

A planning factor used by common carriers to allocate investment in phone equipment, subscriber lines and the non traffic sensitive portion of the central office equipment.

Subscriber Premises Equipment

Cable-related equipment located on the subscriber premises, whether owned by the subscriber or the cable system. This term includes:

  • Subscriber-owned consumer-electronics equipment (TV sets, VCRs, FM tuners, closed-caption decoders).

  • Subscriber-owned terminal devices (generic converters, digital audio tuners).

  • System-owned terminal devices (generic converters, converter/descramblers, digital audio tuners, special equipment to enable simultaneous reception of multiple signals). Compare with Subscriber Terminal.

Subscriber Self Provisioning

Subscriber self provisioning enables the subscriber self-service access to configure his or her own features and services using their PC and a web-based GUI (graphical user interface), e.g. a standard browser. The subscriber would be able to enable new features or modify how the existing ones work. Such features might include caller ID, call forwarding, call transfer, etc.

Subscriber Tap

A device used to take a small portion of signal off a cable and feed it to a subscriber.

Subscriber Television

STV. Also called subscription television. Television in which the subscribers pay a fee for programming as compared with commercial television where they do not.

Subscriber Terminal

The point at which the subscriber-owned cable television equipment is connected to the cable system; typically, a 75-ohm "F"-connector or a 300- ohm balanced line. Compare to Subscriber Premises Equipment.

Subscriber Trunk Dialing

STD. The European version of direct-distance dialing. Pricing for long distance calls is typically done by billing a standard amount of money, e.g. a German Mark, for a length of speaking time, which shortens the further you call. For example. you might get one minute for a Mark if you're calling 50 miles. If you call 200 miles you might only get 20 seconds.

Subscriber Unit

SU. The Radio Frequency (RF) modem used to acquire the airlink; can be an integral part of the Mobile End System (M-ES) or a separate component.

Subscriber Drop

Wire which runs from a cable terminal or distribution point to the subscriber's premises.

Subscription Fraud

Subscription fraud occurs when a cellular subscriber uses false information or a false identity to secure legitimate service, causing the carrier to incur soft- and hard-dollar losses. This type of fraud can be prevented by better credit checks and billing systems as well as through prepay offerings.


A contraction for Subscriber Set, or telephone set.


A method of allocating frequencies in a broadband transmission system. Transmit frequencies are in the range of 5 to 32 megahertz, and receive frequencies are in the range of 54 to 300 megahertz .


An additional phone which has been established as an extension to the main phone or primary line.

Substitute Character

A transmission control character used in place of a character found to be in error.


A word used in voice recognition to mean a type of error that occurs when a word within the active vocabulary is spoken correctly but classified as another word within the vocabulary. This error is usually dealt with during a verification stage in an application, i.e. " you said, 1,2,3...correct?"


The position of a central office in the network hierarchy as it relates to another central office, normally referred to as an access tandem. A central (end) office provides the dial tone point of connection for end users and has its trunking facilities directed to the access tandem (switching point), which allows end users access to a variety of IXCs. The end office is referred to as subtending the access tandem.


A network element (NE) that underlies, or has a lower position than, another network element. For example, a tandem switching system serves to interconnect subtending end offices, or central offices (COs). Similarly, a high-speed carrier-class core router or ATM switch interconnects subtending routers or switches. A long-haul backbone OC-192 SONET fiber optic ring running at 10 Gbps may serve to interconnect subtending OC-48 metropolitan rings running at 2.5 Gbps.

Subtending Tandem

LEC tandem that would be used by a CLEC to connect to an IXC that is not directly interconnected to that CLEC.

Subviral Marketing

Short, email-friendly video clips that appear to spoof a well- known commercial ” a subversive twist on viral marketing. The clips are thought to be commissioned by the companies whose ads are parodied, such as Budweiser, Ford, Levi Strauss, and MasterCard. This definition from Wired Magazine.

Subvoice-Grade Channel

A communications channel of bandwidth narrower than a standard 3Hz voice line. A subvoice-grade channel is usually used for slow data transmission such as teletype or telemetry.

Sucker Trap

A feature of a security firewall. Sucker traps log access attempts, separate legitimate from illegitimate users, and maintain an audit log of the illegitimate.

Suckers Rally

In a bear market, stock prices fall over a long-term. But prices do not fall in a straight line. They occasionally bounce upwards for a few days. As prices rise, some people come to believe that the bear market is over and we're about to end a major bull- market. But then, a week or two later, prices begin to fall again and quickly fall further than the bounce took them up. The bounce becomes known as a suckers rally, also known as a head fake.

Sudden Reputation Death Syndrome

This wonderful definition from Wired Magazine: "The complete and instantaneous loss of all credibility, support and near- term job prospects after being caught up on a high-profile scandal (e.g. Enron's Kenneth Lay and Clinton adviser, Dick Morris)."


Sufism is a mystic tradition in Islam that dates back to the eighth century and the Ottoman Empire. It is best known for its dervishes' dancing , done to achieve a higher state of awareness.


A pejorative term for a professional manager. The term is used by bright, hardworking folks who work for a startup company. Such people, also called ponytails, tend to believe themselves to be very creative. As a mark of their "creativity," they tend to dress casually. When the startup becomes successful, it often goes public or is bought by a large, well-established firm. In come the "suits" ” professional managers who dress in fancy, expensive suits and sport arrogance to match. These professional managers then proceed to mess up the company because they try and install ponderous, "big company" practices - lots of budgeting, procedures and policies ” on a company that succeeded because it was light of foot. The worst of the "suits" are known as "empty suits." See Empty Suit.


A collection. A suite of software tools is a collection of software tools.

Summary Address

An ATM term. An address prefix that tells a node how to summarize reachability information.

Summary Billing

Some telecom carriers will give you one monthly consolidated phone bill ” no matter how many number accounts you have in your billing area. Ask.

Summation Check

A check based on the formation of the sum of the digits of a numeral. The sum of the individual digits is usually compared with a previously computed value.

Sun Microsystems

Sun Microsystems is a Californian computer manufacturer. SUN stands for Stanford University Network. See Java.

Sun outage

A complete blockage of the receiving ability of an earth station whenever the sun passes through the axis of the main beam of its antenna. Because the antenna then "sees" the noise temperature of the sun, the station's G/T is depressed below the minimum required for reception. However, in "looking" at the entire earth, the satellite "sees" only one small shiny point, of the antenna reflecting the sun, so the station may still transmit.

Sun Synchronous

A term describing the fact that the orbits of LEOs (Low Earth Orbiting) and MEOs (Middle Earth Orbiting) satellite systems can be adjusted such that the greatest number of satellites in the constellation are positioned over geographic areas which are in the light of day. At such times, the greatest amount of traffic originates and terminates. See LEO and MEO.

Sun Transit Outage

Satellite circuit outage caused by direct radiation of the sun's rays on an earth station receiving antenna.

Sundown Rule

A rule in voice mail which says that all messages should be returned that day, before the sun goes down.


When telecommuters take on outside projects while working at home for their own employer.


SunOS is Sun Microsystems' implementation of UNIX.


Hardware/software solutions from Sun Microsystems for MS-DOS on SPARC platforms.


SunView is Sun Microsystems' kernel-based window system.

SunXTL Server

Part of Sun Microsystems' XTL Teleservices architecture. Provides multi-client and multi-device support. The server is the central point of contact for all tele- services services. Resource management and security are provided by the server. Communicates with the Sun XTL provider to place and receive telephone calls. An application may access the data associated with a call by acquiring a data stream from the API.

Super DSL

A slang name for a second generation DSL line ” one offering speeds as fast as eight megabits per second downstream (i.e. coming from the central office to the customer).

Super G3

Super G3 is a new unofficial "standard" for higher speed fax machines, which contain a 33.6 Kbps V.34 modem, V8 handshaking and the new ITU-T T.85 JBIG image compression. On most phone lines such a machine should get close to double the speed of the highest speed Group 3 fax machines, namely 14.4 Kbps. But, the JBIG image compression will speed faxing of gray scale images by as much as five to six times. In short, these machines will send faxes much faster ” if they send to a Super G3 machine at the other end. Super G3 is compatible with and can communicate with older fax machines, Group 1, 2, 3 and 3 Enhanced.

Super Server

A file server with more than one CPU (Central Processing Unit). At time of writing this dictionary, a high-end super server might contain four Intel Pentium chips. To take advantage of these super servers, you need an operating system capable of asymmetrical multi-processing, such as Unix and Windows NT Advanced Server.


The latest phase in the development of JANET, the UK educational and research network run by UKERNA. It uses SMDS and ATM to provide multi-service network facilities for many new applications including Multimedia Conferencing.


A term applied to a class of high-speed computers employing advanced technologies such as simplified instruction sets, wide data paths and pipelining.


Superconductors are materials which have no resistance to the flow of electricity. They are widely believed to have great potential for dramatically faster telecommunications switches and computers. In the past, the superconducting state ” zero resistance to the flow of electricity ” could be achieved only by cooling certain metal alloys to temperatures of near absolute zero, or about 460 degrees below zero. Starting in 1986, researchers discovered that ceramic materials could reach superconductivity at temperatures as high as 235 degrees below zero.


The name for Apple's 1.44 Mb floppy that can read and write MS-DOS formatted floppies and Mac formatted disks. DOS floppies require Apple File Exchange or a third party product to read the DOS format.

Superframe Format

  1. The T-Carrier superframe transmission structure consists of 12 DS-1 frames (2316 bits). The DS-1 frame comprises 193 bit positions, the first of which is the frame overhead-bit position. Frame overhead bit positions are used for the frame and signaling phase alignment only. See also DS-1 and T-Carrier.

  2. In digital cellular networks defined in IS-136, a superframe comprises 16 frames. Two superframes comprise a hyperframe. See also IS-136.


Sixty voice channels. In more technical terms: the assembly of five 12- channel groups occupying adjacent bands in the spectrum for the purpose of simultaneous modulation or demodulation.


A type of radio receiver operating on the heterodyne or beat principle. See Heterodyne.


The National Society of Home Builders has registered SmartHouse. BellSouth has trademarked SuperHouse. And GTE has registered SmartPark. One day, fiber optic will snake to everyone's house, bringing the potential of immense information services. Until that day comes they'll be lots of interesting demonstrations at distant trade shows.

Superimposed Ringing

A way of stopping party line phone users from hearing each other's ring by superimposing a DC (direct current) voltage over the ringing signal and using it to alert a vacuum tube or semiconductor device in only the phone instrument that we want to ring. See also Superposed Ringing.


SMG. Six mastergroups each comprised of 10 supergroups each comprised of five groups of 12 circuits totaling 3600 circuits carried as a unit in an analog FDM carrier system; first used in Bell's L4 coaxial cable carrier systems.




An IP (Internet Protocol) term. Supernetting is the linking of multiple IP network address blocks into a "supernet." In the early 1990s, the IETF (Internet Engineering Task Force) approved RFCs ( Requests For Comment) 1518 and 1519, which detail the CIDR (Classless InterDomain Routing) protocol to allow the grouping of multiple Class C subnet address blocks into a single "supernet." BGP-4 (Border Gateway Protocol version 4) supports supernetting. See also BGP, CIDR, IETF, and RFC.

Superposed Circuit

An additional channel obtained from one or more circuits, normally provided for other channels, in such a manner that all the channels can be used simultaneously without mutual interference.

Superposed Ringing

Party-line telephone ringing in which a combination of alternating and direct currents is used, the objective being to only ring the bell in the phone of the one whose call is coming in. See also Superimposed Ringing for a better explanation.


IBM's new name for a mainframe. The name is clearly an attempt to position the mainframe more competitively against the new extremely powerful PCs which are taking over the mainframe's role.


Toby Corey, president of USWeb Corp., defines supersite as an Internet site combining a public Internet site, an extranet for business partners and an administrative intranet. He says a supersite has a common architecture across intranet, Internet, extranet and Web sites. He says it serves multiple audiences and it implements various levels of access control.


A commercial television broadcast station which is transmitted to a cable television headend by a communications satellite and then retransmitted by the cable system to its subscribers. FCC rules provide that a cable television system may carry a superstation under the same conditions that it may carry any other television broadcast station. Examples: WGN-TV and WWOR are superstations (TBS is not a superstation, in spite of its self-proclaimed status as "Superstation TBS."). Compare Origination Cablecasting.


A cable that carries several video channels between facilities of a cable television company. A trunk between the master and the hub headends in a hub CATV system.

Supervised Transfer

In telephony, supervised transfer is a way to transfer the first "leg" of a call to the "second leg" or third party while keeping the first party (typically the originator of the call) "in the loop". In most cases, this is achieved by doing a conference call and then idling the transmit and receive signals to the first party. This keeps the first party in a supervising position, so the second leg can be dropped in order to establish subsequent connections with the first leg of the call. In computer telephony, supervised call transfers are necessary when the application is designed to retain supervision of the call. This means that a caller can be transferred to another system or telephone extension with the VRU (Voice Response Unit) dropping out of the call. This is especially important with some messaging systems that have automated attendant capability. In this case, the VRU will momentarily put the caller on "hold" while determining if the called party is available. This takes into account the call progress tones that are encountered when calling the destination phone. For example, if the VRU detects a busy tone, it will take the caller off of hold and indicate that the extension is busy. The caller is typically offered a chance to try again in a few moments, or to leave a message for the called party.


Supervision of a phone call is detecting when a called party has picked up his phone and when that party has hung up. Supervision is used primarily for billing purposes. Not all long distance carriers have supervision capability. It depends on how "equal accessed" they have chosen to be. See Answer Supervision, Software Supervision and Signaling System 7.


The person responsible for day to day maintenance and operation of a phone system. Typically used in conjunction with an ACD ” automatic call distributor.

Supervisory Call

This service feature allows the attendant, after connecting an incoming CO line or tie line call to the wanted phone, to continuously supervise the call in progress.

Supervisory Control

Characters or signals which automatically actuate equipment or indicators at a remote terminal.

Supervisory Lamp

A lamp which shows the operator whether the person is speaking (off-hook) or is not speaking (on-hook). These days such lamps are called BUSY LAMP FIELDS. In some smaller key systems, all phones have them. Busy lamp fields are an operator's best friend.

Supervisory Program

  1. A program, usually part of an operating system, that controls the execution of other computer programs and regulates the flow of work in a data processing system.

  2. A computer program that allocates computer component space and schedules computer events by task queuing and system interrupts. Control of the system is returned to the supervisory program frequently enough to ensure that demands on the system are met.

Supervisory Relay

A relay which, during a call, is controlled by the transmitter current supplied to a subscriber line to receive from the associated phone signals that control the actions of operators or switching mechanisms.

Supervisory Routine

A routine that allocates computer component space and schedules computer events by task queuing and system interrupts. Control of the system is returned to the supervisory program frequently enough to ensure that demands on the system are met.

Supervisory Signal

  1. Supervisory signals are the means by which a telephone user initiates a request for service; or holds or releases a connection; or flashes to recall an operator or to initiate additional features, for example, 3-way calling. Supervisory signals are also used to initiate and terminate charging on a call. A signal also indicates whether a circuit is in use, or not in use.

  2. A signal used to indicate the various operating states of circuit combinations.


Service Order Supplement. A term that grew out of the Telecommunications Act of 1996, which formally opened the local exchange to competition. A "supplement" is a revision to a service order or ASR (Access Service Request) of sufficient magnitude to require the creation of a new version, which is known as a supplemented service order. See also ASR.

Supplementary Services

Telephone company talk for services above basic ability to make a phone call. Supplementary services include fast dialing, calling line ID, call waiting, call forwarding, and videoconferencing features. Here's a definitions of supplementary services as applied to ISDN service: Additional services, such as hold, conference, and call forwarding, offered to an ISDN customer. Supplementary services are always present if activated at the switch. Although the specific features and call appearances may differ between service providers, supplementary service generally provides users with the ability to connect and disconnect new calls when one (or more) call exists.

Supplementary Telephone Service

The lowest level of service in Windows Telephony Services is called Basic Telephony and provides a guaranteed set of functions that corresponds to "Plain Old Telephone Service" (POTS - only make calls and receive calls). The next service level is Supplementary Telephone Service providing advanced switch features such as hold, transfer, etc. All supplementary services are optional. Finally, there is the Extended Telephony level. This API level provides numerous and well-defined API extension mechanisms that enable application developers to access service provider-specific functions not directly defined by the Telephony API. See Windows Telephony Services.


As specified in IEEE 802.1X for port-based network access control, a supplicant makes requests to an authenticator for access to system resources. The authenticator either grants or denies those requests, depending on whether or not it can authenticate (i.e., validate) the identification of the supplicant, along with its access privileges. A supplicant generally is in the form of client software. An authenticator generally is in the form of software on an authentication server, which is consulted by a router or wireless access point. The term "supplicant" is from middle French (1597) and means one who humbly and earnestly implores or begs.

Supply Chain

All the business activities needed to satisfy the demand for products or services from the initial requirement for raw material or data to the final deliveries to the end user. See Supply Chain Management for a better explanation.

Supply Chain Management

The supply chain is the electronic link between a company and its suppliers and distributors/customers. Supply chain management seeks to apply software, hardware, networking and telecommunications links in order to get the right product to the right customer at the right time. Supply chain management software lets managers study their companies' relationships with suppliers, distributors or retailers so they can better forecast and schedule production and sales. The main objectives of supply chain management are to get the product from the supplier to the customer as cheaply and as fast as possible. Much of supply chain management is done on the Internet or private corporate Intranet.

Supply Chain Software

See Supply Chain Management.

Supply Side Economics

Supply side economics is that branch of economics which believes that tax cuts are the primary engine of economic growth.


A really stupid word. Support is a verb that in the tech world means "This hardware, software has the following feature." An example: "This software supports 32- bit file sharing."

Support Hardware

The racks, clamps, cabinets , brackets, trays, and other equipment that provide the physical means to hold the transmission media and connecting hardware. An AT&T definition.

Support Strand

Called a messenger. A strength element used to carry the weight of the telecommunications cable.

Suppressed Carrier Single-Sideband Emission

A single-sideband emission in which the carrier is virtually suppressed and not intended to be used for demodulation.

Suppressed Carrier Transmission

A transmission technique in which only the sidebands (one or both) are transmitted and the main carrier is not transmitted and thus not used.

Suppressed Voltage Ratings

Several ranges are assigned by UL for grading transient suppression voltages. For instance, a 400 volt rating indicates a maximum peak voltage between 330 and 400 volts, These ratings appear between 300 volts and 6000 volts peak.


First, there were 800 toll-free numbers in North America. Then, in the fall of 1995, the FCC introduced 888 numbers ” another toll-free dialing code, since the 800 code was filling up. The FCC allowed bona fide holders of 800 numbers to request '888' replicas of their 800 numbers. 1-800-FLOWERS could request 1-888-FLOWERS, etc...for all the obvious reasons. Prior to 12/1/95, then current holders of 800 numbers could submit their request that the 888 version be suppressed, i.e. not permitted to be made available for general assignment. Many 800 owners asked for suppression of their numbers. Many asked for their use. In some cases this was successful. In others, some suppressed numbers were installed by other companies later on ” i.e. a screw-up. In short, you have to be ultra -careful with suppression.

Suppressors, Echo

Echo is controlled in long distance circuits with devices called echo suppressors. These devices automatically insert loss in the return path of a four-wire circuit. All long distance circuits are four-wire ” two wires for each of the two paths (receiving and transmitting). The echo suppressor jumps back and forth between the two transmission paths. Properly adjusted, an echo suppressor puts only sufficient loss in a circuit so a listener can interrupt the talker. With very long circuits ” 22,300 miles ” in satellites, a better way is needed. They're called echo cancellers.


A charge imposed in accordance with the Commission's Access Reconsideration decision in CC Docket 78-72, Phase 1, FCC 83-356. released August 22, 1983 and updated too many times since. The monthly charge is about $2.00 and is going up to $3.50. This charge is said to compensate the local phone company for long distance commissions (called settlements and separations) lost and now replaced with per minute access charges.


The word "surf" in its classic sense means to ride the crest of a wave, skimming quickly across the water underneath. The electronic world has adopted that definition of skimming quickly and included it in several definitions. For example, shoulder surfing is gazing quickly over someone's shoulder while they're making a call at a payphone and writing down the user's credit card numbers. Channel surfing is moving from one TV channel to another quickly. Surfing the Web means moving from one Web site to another, jumping around in search of knowledge or amusement, but certainly in a non-linear way. See also Internet and Web Browser.

Surface Acoustical Wave Filter

SAW Filter. Specific type of filter made of piezoelectric material.

Surface Emitting Diode

An LED that emits light from its flat surface rather than its side. Simple and inexpensive, with emission spread over a wide angle.

Surface Mount

With surface mount technology, Components sit on the surface of printed circuit boards and are soldered to conductive pads. In the "thru-the-hole" process, component leads are placed through holes in the boards and are sent through wave soldering for attachment. Surface mount technology is more cost-effective , as it allows for denser packaging on the board and components can be mounted on both sides of the surface.

Surface Outlet

A Communications Outlet (modular jack) that is installed on the surface of the mounting location. The premises wire serving such an outlet may or may not be concealed behind the mounting surface.

Surface Wave

A wave that is guided along the interface between two different media or by a refractive index gradient. The field components of the wave diminish with distance from the interface. Optical energy is not converted from the surface wave field to another form of energy and the wave does not have a component directed normal to the interface surface. In optical fiber transmission, evanescent waves are surface waves. In radio transmission, ground waves are surface waves that propagate close to the surface of the Earth, the Earth having one refractive index and the atmosphere another, thus constituting an interface surface.


See Shoulder Surfing and Channel Surfing.

Surfing the Web

A phrase first used by Jean Armour Polly, a former public librarian working on an article about the Internet in 1992. She wrote "At that time I was using a mouse pad from the Apple Library. The one I had pictured a surfer on a big wave. 'Information Surfer' it said. "Eureka, I said and had my metaphor."


An increase in line voltage that lasts longer than one cycle of the line frequency of 60Hz, the North American frequency or 50Hz in many other countries , especially those running at 240 volts.

Surge Protector

A device which plugs between the phone system and the commercial AC power outlet. It is designed to protect the phone system from high voltage spikes (also called surges) which might damage the phone system. When a surge occurs on the power line, the surge protector sends the overload to ground. How fast it sends it to ground is a subject that could fill a book. The type of surge protector that you buy will be determined mostly by the speed you need to protect your equipment.

Surge Suppressor

See Surge Protector.


The increased flow of current through an electrical device brought about by an instantaneous change in its resistance or impedance.


A property of a system, subsystem, equipment, process, or procedure that provides a defined degree of assurance that the device or system will continue to work during and after a natural or man-made disturbance; e.g. nuclear attack. This term must be qualified by specifying the range of conditions over which the entity will survive, the minimum acceptable level or post-disturbance functionality, and the maximum acceptable outage duration.

Survivable Adaptable Fiber Network

SAFENET. A U.S. Navy experimental fiber-based local area network designed to survive conventional and limited nuclear battle conditions.


We'll all survive. We have no choice. ” Ray Horak, December, 2001, after a horrible year.


A nice name for a wife. Everyone should have such an incredible wife. We got married in 1976. And our relationship has only gotten better since. When friends ask us how we manage such a wonderful marriage, I explain that early on in our marriage we split our responsibilities. Susan handles all the lesser decisions, while I handle all the important decisions. Friends ask "What are examples of the lesser decisions which Susan makes?" I answer: "Decisions such as to how we bring up the kids, where the kids go to school, where we live, what we spend our money on, where and when we will vacation..." Friends then ask what are the sort of decisions I get to make? I answer that it's decisions like whether China should be admitted to the World Trade Organization, whether we should bomb Afghanistan, etc. Susan is the mother of our two children, Claire and Michael, and clearly the boss of us all. After 18 editions, she is almost used to seeing more of my gargantuan monitor than me. On the other hand, if she saw more of me, it's doubtful (in fact, almost certain) that our marriage would not have lasted so long. Most of our friends' marriages haven't. She's a great wife. Everyone should be so lucky. See definitions for Claire and Michael for the rest of the family.


In telephone systems, the tendency of circuits to pick up noise and low frequency induction from power systems. It depends on telephone circuit balance, transpositions, wiring spacing, and isolation from ground.


See Hibernation.

Suspended Ceiling

A ceiling that creates an area or space between the ceiling material and the structure above. See also Plenum.

Suspended Customer

An Worldcom definition. A customer who has requested service but has not yet been installed due to insufficient network capacity or some other operational/administrative constraint.

Suspended On-Demand Connection

The mode of an on-demand connection where the communications line is dropped and the connection sites are actively spoofing.

Suspension Bridge

When a suspension bridge was being built over the gorge near Niagara Falls, New York, there was no way a boat could carry the necessary suspension wires across the violent waters. The bridge's builders were inspired to offer $5.00 to the first boy to fly a kite from the American to the Canadian side. It worked. Once the kite string made the crossing, a succession of heavier cords and ropes tied to the kite string and each other were pulled over until the first length of cable finally spanned the river .

Sustaining Engineering

An endeavor in which a company devotes a bunch of people to maintain the quality of engineering on existing products. Such group does not focus on new product.


  1. An ATM term. System Under Test: The real open system in which the Implementation Under Test (IUT) resides.

  2. Stupid User Tricks. Also called ESO, or Equipment Superior to Operator. When closing help desk tickets, it describes situations where the problem was user stupidity, such as the power cord not plugged in, the monitor unplugged, the keyboard not attached, etc.


Silicon Valley, California. See Silicon Valley.


  1. Switched Virtual Circuit. A virtual circuit connection established across a network on an as-needed basis and lasting only for the duration of the transfer. The datacom equivalent of a dialed phone call, the specific path provided in support of the SVC is determined on a call-by-call basis and in consideration of both the end points and the level of congestion in the network. SVCs are used extensively in X.25 networks, and increasingly in Frame Relay networks. SVCs are much more complex to provision than are PVCs (Permanent Virtual Circuits), but perform much better as they effectively provide automatic and dynamic network load-balancing. In other words, SVCs are set up in consideration of the load on the network, and its subnetworks, in order that the least congested path be established and, therefore, that the data transmission receive the lowest possible level of delay. See also PVC, VC and VCC.

  2. Switched Virtual Call. Basically another way of saying switched virtual circuit. See above


Switched Virtual Channel Connection: A Switched VCC is one which is established and taken down dynamically through control signaling. A Virtual Channel Connection (VCC) is an ATM connection where switching is performed on the VPI/VCI fields of each cell.


Simultaneous Voice Data. In the fall of 1994, the term began to apply to several techniques for putting voice conversations and data transfers on the same analog phone line. Some of these techniques involve interrupting the voice conversation while data is transferred. Others involve transferring the data and voice simultaneously on different bandwidths.


Super Video Graphics Array. An extension of the VGA video standard. SVGA enables video adapters to support resolutions of up to 800 x 600 pixels with up to 16.7 million simultaneous colors, which is known as true color because it's the number of colors someone once figured is in a Kodachrome slide. See also VGA. UGVA stands for Ultra Video Graphics Array and refers to 1024 x 768.


Subscriber Verification Number. Number issued by the long-distance carrier to confirm the order for long distance service.


Switched Virtual Path Connection: A Switched Virtual Path Connection is one which is established and taken down dynamically through control signaling. A Virtual Path Connection (VPC) is an ATM connection where switching is performed on the VPI field only of each cell.


A new holding company that will control much of Russia's telecommunications industry. Svyazinvest was originally conceived both as a holding company for the state's interests in 86 local telephone firms across Russia as a competitor for Rostelcom, a state-run near-monopoly in long distance and international telephony. But, later in the planning, the state's 38% shareholding in Rostelcom was dumped into Svyazinvest. According to the Economist Magazine, Svyazinvest's bosses will therefore have power over almost all of Russia's communications systems (in many regions, the local phone companies also hold the first cellular telephone licenses.)


Station Wire.


Switch of Activity.


Scientific Wild Ass Guess. A means of coming up with some figures without all the facts or engineering spec being in place based on known information and past history. SWAG is more accurate than a guess and more valuable than an opinion.


  1. This came from an issue of Internet Week in the Winter of 1998. Seeking to further leverage the ability of the Web to link business partners, a group of vendors led by Netscape, Sun Microsystems and Hewlett-Packard earlier this week proposed a standard to tie together disparate workflow systems on an intranet or over the Internet. The trio, along with 20 other vendors, said they would support the Simple Workflow Access Protocol (SWAP), a proposed Internet standard that would allow disparate workflow engines to manage, monitor, initiate and control the execution of workflow processes between one another within an intranet or over the Internet.

  2. Shared Wireless Access Protocol. A specification from the Home RF (Radio Frequency) Working Group intended to enable interoperability of electronic devices from a large number of manufacturers, while providing the flexibility and mobility of a wireless solution. SWAP is expected to yield a wireless home network to share voice and data communications between devices such as PCs, peripherals, PC-enhanced cordless phones, headsets, and other devices yet to be developed. SWAP also is intended to allow the sharing of a single Internet connection amongst multiple such devices. SWAP is an extension of DECT (Digital Enhanced Cordless Telephone) and WLAN (Wireless Local Area Network) technologies, and supports both TDMA (Time Division Multiple Access) for interactive voice and other real-time applications, and CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) service for high-speed packet data delivery. SWAP runs in the unlicensed ISM (Industrial Scientific and Medical) band in the 2.4 GHz range, and employs FHSS (Frequency Hopping Spread Spectrum) at 50 hops per second. Data rates are at 1 Mbps using 2FSK (Frequency Shift Keying), 2 Mbps using 4FSK, and 10 Mbps using an undefined modulation technique. SWAP will support up to 127 devices per network, and up to six full-duplex voice conversations. Data security is through the Blowfish encryption algorithm, and data compression through the LZRW3-A algorithm. See also HomeRF and HomeRF Working Group.

Swap File

Some operating systems and applications let you use more memory than what you have in RAM. They do this by pretending that part of your hard disk is RAM memory. They do this by creating a swap file on your hard disk and swapping memory back and forth. Some computer systems call this virtual memory. You need to be careful with swap files. Never turn your machine off when you have applications running. If you do you're likely to leave a huge swap on your hard disk, which you may not find (it's hidden) and which your system may not dispose of. To get back the space on your hard disk, you'll need to erase it separately.


Standard Wireless AT Command Set. An extension to the Hayes AT command set to support wireless modems, such as those used in standard AMPS analog cellular phones.


Serving Wire Center. The service provider's (usually telephone company) wire center (i.e., Central Office) to which you are connected.


Swedish Board for Technical Accreditation. They have established two standards, which effectively limit radiation emissions, MPR1 and MPR2. These standards specify maximum values for both alternating electric fields and magnetic fields and provide monitor manufacturers with guidelines in creating low emission monitors. There is, as yet, no definite proof of harm from normal computer monitors . But the argument goes that they weren't so sure about nicotine in cigarettes 30 years ago. And look at us 30 years later.

Sweep Acquisition

A technique whereby the frequency of the local oscillator is slowly swept past the reference to assure that the pull-in range is reached.

Sweep Test

Manufacturers use a sweep test to test the frequency response of a metallic cable as a quality control mechanism. The sweep test involves the checking of frequency response through generating an RF (Radio Frequency) voltage that is varied back and forth in a frequency range at a constant rate.


An increase from nominal voltage lasting one or more line cycles.


Abbreviation for SWITCH HOOK. Originally referred to an actual hook on older phones that held the receiver, and sprang upward to close a switch and activate the phone when the receiver was picked up. Today the term refers to any of various buttons and plungers that are pressed down and released when the handset is put down (physically "hung up" in the old days) and picked up.


Society for Worldwide Interbank Financial Telecommunications.


Special Working Interest Groups. see


Slow, graceful , undesired movements of display elements, groups, or images about their mean position on a display surface, such as that of a monitor. Swim can be followed by the human eye, whereas jitters usually appears as a blur.


SWIP Shared Whois Project. When ARIN allocates a block of IP addresses to an ISP, they create a record of who has been assigned those addresses. If the ISP reassigns some of the IP addresses to a customer, then ARIN's records must be updated to show the new assignee. The e-mail based interface to ARIN that allows an ISP to make these changes is called SWIP. The act of making this changes is called "SWIPPing." SWIP rhymes with hip not hype.

Swiped Out

An ATM or credit card that has been rendered useless because the magnetic strip is worn away from extensive (and expensive) use.

Swiss Army Knife

The one tool to have when you can't have more than one. Be sure it has a normal screwdriver, a phillips head screwdriver and a pair of scissors. A corkscrew also is useful.


A mechanical, electrical or electronic device which opens or closes circuits, completes or breaks an electrical path, or selects paths or circuits. Switches work at Layers 1 (Physical) and 2 (Data Link) of the OSI Reference Model, with emphasis on Layer 2. A switch looks at incoming data (voice data, or data data) to determine the destination address. Based on that address, a transmission path is set up through the switching matrix between the incoming and outgoing physical communications ports and links. Data switches (e.g., LAN switches and packet switches) also typically contain buffers, which can hold data packets in temporary memory until the necessary resources are available to allow the data packets to be forwarded. Voice switches, of course, don't, because you can't delay voice. Switches work link-by-link, with multiple switches typically being involved in complex networks; each switch forwards the data on a link-by-link ( hop-by-hop ) basis. Routers are highly intelligent data switches which are capable of setting up paths from end-to-end, perhaps in consideration of the level of privilege of the user and application. Routers commonly are used at the edges of complex data networks, where intelligence is required to set up appropriate network paths. Although such intelligent decisions impose some delay on the packet traffic, they are made only at the ingress and egress edges of the network. The routers often instruct switches in the core of the network, where speed is of the essence ” switches aren't as intelligent as routers, but they are faster and less expensive. See also Ethernet Switch, OSI Reference Model and Router.

Switch Based Resellers

Switch-based resellers lease facilities from national carriers or large private line networks. They resell services provided over those facilities under their own name and provide sales, customer service, billing and technical support. Switch-based resellers own or lease their own switching equipment and, in some cases, own their transmission facilities. they typically provide originating service on a regional basis. See also Switchless Resellers.

Switch Busy Hour

The busy hour for a single switch.

Switch Control

The technique by which a switching system responds to signals and directs the switching network.

Switch Domain

An SCSA definition. A single instance of a particular technology-specific connection type. See S.100.

Switch Driver

Protocol Mapper Code running on a Telephony Server that translates between a particular switches proprietary switch-server protocol and one of the specified computer telephony integration (CTI) protocols. See Protocol Mapper.

Switch Fabric

An SCSA definition. The facility for connecting any two (or more) transmitting or receiving Service Providers.

Switch Fabric Controller

An SCSA definition. A technology-specific, replaceable ASP within the SCSA server. The SFC is designed to support both the internal connectivity within the group and the complex, multiparty call processing applications not directly addressed by the functionality of the Group.

Switch Feature

A service provided by the switch that can be invoked by a computing domain or by manual telephone activity. "Do not disturb" is an example of a switch feature.

Switch Hook

It is also called the Hook Switch. A switch hook or hook switch was originally an electrical "switch" connected to the "hook" on which the handset (or receiver) was placed when the telephone was not in use. The switch hook is now the little plunger at the top of most telephones which is pushed down when the handset is resting in its cradle (on-hook). When the handset is raised, the plunger pops up (the phone goes off-hook). Momentarily depressing the switch hook (under 0.8 of a second) can signal various services such as calling the attendant, conferencing or transferring calls. See also Switchhook Flash.

In ISDN, the AT&T ISDN sets have several switch hooks; one for the handset, one for the speakerphone, a "virtual" switch hook, and if an adjunct is attached, an adjunct switch hook. If all switch hooks are "on-hook" or hung up, the ISDN set is on-hook. If any switch hook is "off-hook," then the ISDN set is off-hook. If more than one switch hook is off-hook, the ISDN set uses a complex algorithm to determine whether the handset, the speakerphone, or the adjunct has precedence (only one can be used at a time).

Switch Hook Flash

A signaling technique whereby the signal is originated by momentarily depressing the switch hook. See Switch Hook.

Switch Interface

The Ethernet MAC controller interface. In general, a switch interface on a switch is the same as a port. However, the number of interfaces does not necessarily correspond to the number of ports. For example, a MAB port on a switch may be a 4-port repeater.

Switch Message

Information that originates in a switch. A Call-Progress Event Message is one category of switch messages. Delivered is an example of a call-progress event message.

Switch Network

The portion of a switch that provides the connection between lines and trunks terminated in the system.

Switch Over

When a failure occurs in the equipment, a switch may occur to an alternative piece of equipment.

Switch Port

An SCSA definition. A resource that allows a Group to communicate with another Group. All Groups implicitly possess a Switch Port as a secondary resource, but in order to use it, the application must explicitly connect the Switch Ports of two Groups.

Switch Redirect

A central office service which instantly, on command, redirects thousands of phone numbers to different phone numbers. Such a service has great use in a disaster.

Switch Room

The room in which you put phone equipment. Also called the Phone Room. (What else?) The Phone Room should be large, clean and should stay at roughly seventy degrees and 50% humidity. You, the customer, are responsible for the quality and condition of your phone room. The messier it is, the hotter it is, the dirtier it is, the poorer your phone system (and its technicians) will function.

Switch Tag

A switch tag is a series of numbers and or letters either at the beginning or end of a recording that identifies who originated the recording. A switch tag is be often used by a local or long distance phone company, wired or wireless.

Switch Tender

In the old, old days, the switch tender was the person who took care of the switch that moved trains from one track to another. That person often stayed for many hours a day in a small hut next to the track. Based on timetables and telegraph and phone communications with central train dispatch, he would change the switch and thus move incoming trains to the right track. The job of being a switch tender is now obsolete as switches are now changed remotely by signals over phone lines. The expression "sleeping at the switch" came from the switch tender profession. Sleeping at the switch could cause train derailments and dead passengers. Sleeping was not a career-enhancing strategy. See Switch Train.

Switch Train

In a telecom circuit (typically a step-by-step central office), the series of switching devices which a call moves through in sequence.

Switchable Hubs

Feature ports that permit additional stackable hubs to be connected for expanded capacity. Special software is used to reassign the ports or switch the ports off and on.


The attendant position of a PBX. Most of them don't actually have "boards" (they were big), they have consoles (they're much smaller and they fit on desks). Switchboards are desks.

Switchboard Cable

A cable used within and between the central office main frames and the switchboard.

Switched 56

A switched data service which lets you dial someone else and transmit at 56 Kbps over the PSTN (Public Switched Telephone Network). Actually Switched 56/64, Switched 56 also is available at 64 Kbps, where the carrier supports non- intrusive signaling and control. It is a circuit-switched service, letting the user transmit data at 56/64 Kbps over a four-wire, digital, synchronous network. The cost of a Switched 56/64 call is calculated based on duration and time of day, with discounts for non-prime time calls; discounts also apply according to day of week, holidays, and so on.

Provided by LECs, Switched 56/64 was the first VPN (Virtual Private Network) service offered. The term "VPN" currently is applied to IXC services, with bandwidth available at 56/64 Kbps, increments of 56/64 Kbps, 384 Kbps, and 1.544 Mbps (T1). Switched 56/64 offers a high degree of redundancy, flexibility and scalability. It often is used as an alternative to private, leased-line networks ” or as a backup for them.

Applications for Switched 56 include videoconferencing, high speed data transfer, digital audio broadcasting, Group IV fax and remote LAN access for telecommuters. It also is used as an access technology for IXC-provided VPNs. While it is widely deployed, Switched 56/64 faces a great deal of pressure from ISDN BRI, which offers as much as 144 Kbps, where available. Over time, Switched 56/64 will disappear for good in North America. See also VPN.

Switched Access

A method of obtaining test access to telecommunications circuits by using electromechanical circuitry to switch test apparatus to the circuit.

Switched Access Line Service

All residential and most businesses use this type of telephone access. It refers to the connection between your phone and the long distance companies' switch (POP) when you make a regular local or long distance telephone call over standard phone lines.

Switched Carrier

In data terms, physical line specification selection indicating a half duplex line in a bisync network.

Switched Circuit Automatic Network

SCAN. A service arrangement at certain Telco premises to interconnect private line telephone service channels of a switched service network provided to certain agencies of the federal Government.

Switched Circuit Ordering And Tracking System

SCOTS. MCI's automated tracking and order processing system for Dial up products, IMTs, and the MCI switched network.

Switched DAL

Switched Dedicated Access (Egress) Line. Dedicated trunk group (T-1, etc.) circuit(s) used to access (1+, etc.) or egress (800, etc.) through normal network switching facilities. The Switched DAL is dedicated to a particular inbound or outbound call type.

Switched Digital Services Applications Forum


Switched Ethernet

Ethernet is the most common local area network. It is a shared network in which each piece of information being transmitted passes by each computer (or workstation) on the network. Information is sent in packets. Each packet contains an address representing which computer (or workstation) the packet is destined for. All other computers on the Ethernet network ignore the packets. If there's a lot of traffic, the time to transmit and receive slows down dramatically. Instead of getting the full 10 megabits per second, transmission speeds might get as slow as 100,000 bits per second. One way of solving this problem is switched Ethernet. Here's how it works. Imagine you have an Ethernet network with 100 users. Fifty of them are on the tenth floor. Fifty of them are on the eleventh floor. We break the cable between the two floors and insert a device known as an Ethernet Switch. Essentially we now have two separate, but joined networks. All the traffic from the tenth floor to the tenth floor stays on the tenth floor. Ditto for the eleventh floor. The duty of the Ethernet switch is to twofold: First to keep traffic from the two floors separate, i.e. no traffic from the tenth to the eleventh. Second, to send traffic from the tenth floor, which is destined for the eleventh, to the eleventh and vice versa. Thus an Ethernet switch's function is to split an Ethernet network so each piece of the network can use the full data transmission capacity. When you set up a an Ethernet switch, you want to make sure that "communities of interest" are on the same "floor" (i.e. Ethernet segment). Let's say 90% of the email, which your marketing department sends, is destined for members of your marketing department. Then it makes sense to have your marketing department on one Ethernet segment. An Ethernet switch is far more expensive than an Ethernet hub, which simply joins computers and/or workstations to an Ethernet network and makes sure that all the packets transmitted bypass all the computers and/or workstations on the Ethernet network.

Switched LATA Access

An LEC service offering under tariff that provides for a switched communications path between an long distance company POP (Point of Presence) and the premises of its end users. It includes all LATA access services that use an LEC switching system (EO or AT).

Switched Line

A circuit which is routed through a circuit switched network, such as the telephone or telex network.

Switched Local Service

You pick up the phone. You dial a local number. Bingo, you have switched local phone service. The reason this trivial definition is even in this dictionary is because many states in the U.S. now ” finally ” allow companies to offer local switched telephone service in competition with the established company, e.g. Nynex or Southern Bell. Previously, they had only allowed competition in leased lines. And then previous to that they had not allowed any competition in any area of local phone service. So things are changing, albeit very very slowly.

Switched Loop

In telephony, a circuit that automatically releases connection from a console or switchboard, once connection has been made, to the appropriate terminal. Loop buttons or jacks are used to answer incoming listed directory number calls, dial "O" internal calls, transfer requests , and intercepted calls. The attendant can handle only one call at a time.

Switched Loop Operation

Each call requiring attendant assistance is automatically switched to one of several switched loops on an attendant position.

Switched Message Network

A network service, such as Telex or TWX, providing interconnection of message devices such as teletypewriters.

Switched Multibeam

A type of "smart" antenna used in Wireless Local Loop (WLL) systems. Switched multibeam antenna detect signal strength in a given connection, and select a beam between an end device and one of perhaps many WLL antennas, locking in on the strongest signal. Also in the general category of smart antenna systems is the phased array approach. See also Phased Array and WLL.

Switched Multimegabit Data Service

SMDS. A 1.544 Mbps public data service with an IEEE 802.6 standard user interface. It can support Ethernet, Token Ring and FDDI (OC-3c) LAN-to-LAN connections. See SMDS and SMDS Interest Group.

Switched Network


Switched Private Line Network

A network which results from combining point-to-point circuits with switches.

Switched Service Network

A private line network that uses scan and/or CCSA type common control switching.

Switched Transport

A name for telephone traffic between the local exchange carriers' Central Offices and an interexchange carrier's point of presence (POP). Switched transport is generally provided on a monopoly basis as part of a LEC's network.

Switched Virtual Circuit

SVC. A call which is only established for the duration of a session and is then disconnected. See SVC.


Also called a production switcher. A video term. A device that allows transitions between different video pictures. May also contain special effects generators.


A synonym for hookswitch or hook switch. Also spelled switch hook. See Switch Hook.

Switchhook Flash

A signaling technique whereby the signal is originated by momentarily depressing the switchhook. The technique is sensitive to variations in the time of depression. Too short a signal will not be recognized, and too long a signal will be interpreted as a disconnect signal.


Connecting the calling party to the called party. This may involve one or many physical switches.

Switching Arrangement

A circuit component which enables a Customer to establish a communications path between two phones on a network.

Switching Centers

There are four levels in the North American switching hierarchy run at AT&T. They are: Class 1 ” Regional Center, Class 2 ” Sectional Center, Class 3 ” Primary Center, Class 4c ” Toll Center and Class 4P ” Toll Point. In addition, the local Bell operating companies run a fifth level in the hierarchy, called the Class 5 ” End Office.

Switching Equipment

Premises equipment which performs the functions of establishing and releasing connections on a per call basis between two or more circuits, services or communications systems.

Switching Equipment Capacity

A telephone company term. The capacity of switching equipment is expressed in network access lines. these components can be grouped into four categories. For D&F Chart purposes, the four categories are:

  1. Dial Tone Equipment;

  2. Talking Channels;

  3. Switching Control; and

  4. Trunk Terminations.

Switching Fee

A one-time, per-line fee imposed by the LEC to reprogram their switching system to change your default long-distance carrier. Some resellers and IXCs will reimburse new subscribers for this fee.

Switching Hub

A multiport hub that delivers the full, uncontested bandwidth between any pair of ports. An intelligent switching hub also provides bridging and multi- protocol routing capabilities.

Switching Office

A telephone company office containing a switch.

Switching Point

Same as end office and intermediate office.

Switching System

  1. An assembly of equipment arranged for establishing connections between lines, lines to trunks, or trunks to trunks.

  2. An ATM term. A set of one or more systems that act together and appear as a single switch for the purposes of PNNI routing.

Switchless Resellers

A switchless reseller buys long distance service in bulk from a long distance company, such as AT&T, and resells that service to smaller users. It typically gets its monthly bill on magnetic tape, then rebills the bulk service to its customers. A switchless reseller owns no communications facilities ” switches or transmission. It has two "assets" ” a computer program to rebill the tape and some sales skills to sell its services to end users. The profit it makes comes from the difference between what it pays the long distance company and what it is able to sell its services at. Switchless resellers are also called rebillers. It's not an easy business to be in, since you are selling a long distance company's services to compete against itself. See also Aggregator and Facilities Based Carrier.


Step-by-Step. The first generation of automatic dial telephone systems, SxS systems were invented by Almon B. Strowger, a Kansas City (MO) undertaker in 1891. It seems as though Mr. Strowger was increasingly frustrated with the local telephone operator, who was directing Mr. Strowger's business calls to a competing undertaker, who also just happened to be her husband. When his complaints to the telephone company had no impact (Sound familiar?), he invented a switching system that effectively made operators obsolete in the switching of local calls, at least. Strowger's original system, which was based on earlier Bell System patents, could serve 99 customers. The invention formed the foundation for his founding Automatic Electric, which later became the manufacturing arm of GTE, which much later was merged into Verizon. SxS switches are electromechanical and circuit-switching. They comprise a number of "line finders ," to which groups of customers are assigned for dial tone. As the user dials the digits comprising a telephone number, originally using a dial telephone, the electrical circuit between the set and the switch is made and broken. The electrical pulses that are generated by this process cause successive mechanical SxS "line selectors" to click across contacts to set up the conversation path. Digit-by-digit the line selectors set up the call, step-by-step, hence the name. Just as SxS switches rendered obsolete manual cordboards (and the operators who ran them), they in turn were rendered obsolete by electromagnetic Xbar (Crossbar) technology, which later was rendered obsolete by ECC (Electronic Common Control) technology. A lot of SxS switches remain in service, however, most especially in developing countries. SxS switches served in various capacities, including COs (Central Offices), tandems, and PBXs. See also Cord Board, ECC, and Xbar.

Symbian Connect

The PC-based Symbian Connect is a system for data synchronization, file management, printing via PC, application installation from a PC, and other utility functions allowing Symbian OS phones to integrate effectively with PC and server-based data.

Symbian OS

An operating system for cell phones produced by a company that does not sell cell phones, just the software to make them better. The company is called Symbian. According to the company's web site,, Symbian is a software licensing company, owned by wireless industry leaders , that is the trusted supplier of the advanced, open, standard operating system ” Symbian OS ” for data-enabled mobile phones. Symbian was established as a private independent company in June 1998 and is owned by Ericsson, Nokia, Matsushita (Panasonic), Motorola, Psion and Sony Ericsson. Headquartered in the UK, it has offices in Japan, Sweden, UK and the USA. The world's first open Symbian OS phone became available in the first half of 2001: the Nokia 9210 Communicator.


  1. An abbreviated, predetermined representation of any relationship, association or convention.

  2. In digital transmission, a recognizable electrical state which is associated with a signal element, which is an electrical signal within a defined period of time. In a binary transmission, for example, a signal element is represented as one of two possible states or symbols, i.e., 1 or 0.

Symbol Rate

See 802.11a.

Symbolic Debugger

A debugger is a wholly- or partly-memory-resident program that lets you closely monitor and control execution of an application under development. At the most basic level, a debugger lets you look at running machine code, and fiddle around with the contents of memory ” great if you understand machine code (and are looking at machine code you've written from scratch). Not great if you don't know machine code, or are looking at machine code output by a high-level language compiler (e.g., C++ compiler). A basic symbolic debugger references the symbol table of an executable, providing readable variable names , function entry-points, etc., more or less as they appear in source. Easier for machine-language folks (because of the labels). Not much easier for high-level language folks, because you're still dealing with machine code. A source- level symbolic debugger references both the symbol table of an executable and various files produced during compilation; and lets you work with high-level language source directly, during target program execution. Fully-integrated debuggers like this are built into Microsoft's Visual/X products. Functions common to most debuggers include the ability to set "breakpoints" (i.e., run the program until you reach this step, then stop), "watch variables " (i.e., show me how the value of this variable changes ” and possibly stop if it assumes a predetermined value), "single-step execution" (i.e., do this step and stop), change variable values in mid-execution, etc.

Symbolic Language

A computer programming language used to express addresses and instructions with symbols convenient to humans rather than machines.

Symbolic Logic

The discipline in which valid arguments and operations are dealt with using an artificial language designed to avoid the ambiguities and logical inadequacies of natural languages.


Balanced in proportion. A symmetric telecom channel has the same speed in both directions. It's important to contrast symmetric with full duplex which is transmission in two directions simultaneously, or, more technically, bidirectional, simultaneous twoway communications. For example, ISDN BRI provides full duplex, symmetric bandwidth, as each of the two B channels provides 64 Kbps in each direction and the D channel operates at 16 Kbps in each direction. Symmetric also can refer to the physical topology of the network. For example, a point-to-point circuit connects one device directly to one other device. Asymmetric, on the other hand, refers to something which is not perfectly balanced. See the next several definitions. See also Asymmetric, Bps, Byte and Full Duplex.

Symmetric Connection

A connection with the same bandwidth (i.e. speed) in both directions. See also Bps, Byte, Full Duplex and Symmetric.

Symmetric Cryptography

Branch of cryptography involving algorithms that use the same key for two different steps of the algorithm (such as encryption and decryption, or signature creation and signature verification).

Symmetric Multiprocessing

SMP. A type of multiprocessing in which multiple processors execute the same kernel-level code at the same time, sharing a single copy of the operating system. The degree of symmetry can vary from limited, where there is very little concurrency of execution, to the theoretically ideal fully-symmetric system where any function can be executed on any processor at any time. Processors within the same system share all processes and resources, including disk I/O, network I/O and memory. Compare to Asymmetrical Multiprocessing, wherein processors in the same or different systems are dedicated to specific tasks, such as disk I/O, network I/O or memory management. They off-load these tasks from the main system CPU, which generally is responsible for running the operating system. Each processor usually has its own dedicated memory.

Symmetrical Channel

A channel in which the send and receive directions of transmission have the same data signaling rate.

Symmetrical Compression

A compression system which requires equal processing capability for compression and decompression of an image. This form of compression is used in applications where both compression and decompression will be utilized frequently. Examples include: still-image databasing, still-image transmission (color fax), video production, video mail, videophones, and videoconferencing.

Symmetrical Digital Subscriber Line


Symmetrical Pair

A balanced transmission line in a multipair cable having equal conductor resistances per unit length, equal impedances from each conductor to earth, and equal impedances to other lines.


Sending the same audio stream out from several Web sites simultaneously. You do this because one site would not accommodate the demand for this stream.




Synchronous. SYN and syn both identify some form of synchronization between devices supporting a data session. In TCP, for example, SYN is a single bit in a field of six control bits in the the TCP header. The SYN bit is used to synchronize sequence numbers in order to ensure that every octet in a given TCP packet is received and acknowledged . In synchronous transmission, syn is a control character in character-oriented protocols used to maintain synchronization, and as a time-fill in the absence of data. The sequence of two SYN characters in succession is used to maintain synchronization following each line turnaround . Contrast with Flag.

Syn Flood

A denial of service attack on a computer system in which the attackers hack into a large number of computers, then use those machines to bombard the victim site with requests to start an ecommerce session. The large number of requests overwhelms the victim's computers, preventing legitimate customers from gaining access to the site. See also Smurf Attack.


  1. Synchronization character.

  2. The portion of an encoded video signal that occurs during blanking and is used to synchronize the operation of cameras , monitors, and other equipment. Horizontal sync occurs within the blanking period in each horizontal scanning line, and vertical sync occurs within the vertical blanking period.

Sync Bits

Synchronizing bits (more properly bytes or characters) used in synchronous transmission to maintain synchronization between transmitter and receiver.

Sync Generator

A video term. A device that generates synchronizing pulses need by video source equipment to provide proper equipment or studio timing. Pulses typically produced by a sync generator include subcarrier, burst flag, sync, blanking, H & V drives, color frame identification, and color black.

Sync Pulse

Timing pulses added to a video signal to keep the entire video process synchronized in time.


Synchronization Markup Language is an industry-wide effort to create a single, common data synchronization protocol optimized for wireless networks. SyncML's goal is to have networked data that support synchronization with any mobile device, and mobile devices that support synchronization with any networked data. The SyncML structured data layer will use XML wherever appropriate. SyncML is intended to work on transport protocols as diverse as HTTP, WSP (part of WAP) and OBEX, and with data formats ranging from personal data (e.g. vCard & vCalendar) to relational data and XML documents. The SyncML consortium was set up by IBM, Nokia and Psion among others. Symbian is a sponsor of the SyncML consortium.

Synchronet Service

Dedicated point to point and multipoint digital data transmission service offered by BellSouth at speeds of 2.4, 4.8, 9.6, 19.2, 56 and 64 Kbps.


  1. A networking term which means that the entire network is controlled by one master clock and transmissions arrive and depart at precise times so that information is neither lost nor jumbled. For a bigger explanation, see Network Synchronization and Synchronous.

  2. An uninterruptible power supply (UPS) definition. Specially designed circuitry is "synchronized" to your AC power outlet to ensure continuity of power. Without this feature, power reversal can occur on the input.

  3. A multimedia term. Synchronization is very precise real-time processing, down to the millisecond. Some forms of multimedia, such as audio and video, are time critical. Time delays that might not be noticeable in text or graphics delivery, but are unacceptable for audio and video. Workstations and networks must be capable of transmitting this kind of data in a synchronized manner. Where audio and video are combined, they must be time stamped so that they can both play back at the same time.

  4. Start with a database on your server. Now, take a copy of part of it on your laptop ” for example, your very own sales leads. Go traveling. Come back in a week. You want to update the database with your changes. But you don't want to destroy other peoples' changes. Some people are calling this "file synchronization." Synchronization is a critical part of what is increasingly being called "Groupware." See also Replication.

  5. A Video term referring to the timing of the vertical and horizontal presentation of the multiple still images. Vertical synch prevents the picture from flipping, or scrolling unnaturally. Horizontal synch keeps the picture from twisting. If both vertical and horizontal are out of synch, the picture looks truly wretched.

Synchronization Bit

A binary bit used to synchronize the transmission and receipt of characters in data communications.

Synchronization Bits

Bits transmitted from source to destination for the purpose of synchronizing the clocks of the transmitting and receiving devices. The term "synchronization bit" is usually applied to digital data streams, whereas the term "synchronization pulse" is usually applied to analog signals.

Synchronization Code

In digital systems, a sequence of digital symbols introduced into a transmission signal to achieve or maintain synchronism.

Synchronization Pulses

Bits transmitted from source to destination for the purpose of synchronizing the clocks of the transmitting and receiving devices. The term "synchronization pulse" is usually applied to analog signals, whereas the term "synchronization bit" is usually applied to digital data streams.


The word synchronize means "to cause to match exactly." When you're synchronizing, you're causing one file on one computer to precisely match another one on another computer. Why would you want to do this? Let's say you have a database of sales contacts on a file server. One of your salesman takes a copy of his sales contacts with him on his laptop. He travels and makes changes to his contacts. Now he dials into the office via modem and wants to "synchronize" his changed database with the now- changed main database, and make them both the same, i.e. into synch. This process is far more difficult than it sounds because it means allowing for the changes made at the server and by the salesman . You have to set up elaborate rules.

In operating systems, such as Windows NT, the word "synchronize" has a narrower meaning. Windows NT instruction manual defines "synchronize" as "to replicate the domain controller to one server of the domain, or to all the servers of a domain. This is usually performed automatically by the system, but can also be invoked manually by an administrator." See also Replicate.


Achieving and maintaining synchronism. In facsimile, achieving and maintaining predetermined speed relations between the scanning spot and the recording spot within each scanning line.

Synchronizing Pilot

In FDM, a reference frequency used for achieving and maintaining synchronization of the oscillators of a carrier system or for comparing the frequencies or phases of the currents generated by those oscillators .


The condition that occurs when two events happen in a specific time relationship with each other and both are under control of a master clock. Synchronous transmission means there is a constant time between successive bits, characters or events. The timing is achieved by the sharing of a single clock. Each end of the transmission synchronizes itself with the use of clocks and information sent along with the transmitted data. Synchronous is the most popular communications method to and from mainframes. In synchronous transmission, characters are spaced by time, not by start and stop bits. Because you don't have to add these bits, synchronous transmission of a message will take fewer bits (and therefore less time) than asynchronous transmission. But because precise clocks and careful timing are needed in synchronous transmission, it's usually more expensive to set up synchronous transmission. Most networks are synchronous these days. See Asynchronous and Network Synchronization.

Synchronous Completion

A computing domain issues a service request and need not wait for it to complete. If the computing domain waits for this completion, this is known as synchronous, but if it is sent off to another system entity and the computing domain goes on to other activities before the function completes (and the system later sends a message to the computing domain announcing the function's completion), that completion is known as asynchronous.

Synchronous Control Character

SYN. A transmission control character used in synchronous transmission to provide a signal in the absence of any other character. SYN is defined by IBM Corp's Binary Synchronous Communications (BSC) protocol.

Synchronous Data Link Control

SDLC. A data communications line protocol associated with the IBM Systems Network Architecture. See Systems Network Architecture.

Synchronous Data Network

A data network in which synchronism is achieved and maintained between data circuit-terminating equipment (DCE) and the data switching exchange (DSE), and between DSEs. The data signaling rates are controlled by timing equipment within the network. See Network Synchronization.

Synchronous Data Transfer

A physical transfer of data to or from a device that has a predictable time relationship with the execution of an I/O (Input/Output) request. See Synchronous.

Synchronous Digital Hierarchy

SDH. A set of international standards developed by the CCITT (now ITU-T) for fiber optic transmission systems. The SDH standards are an international superset of the original SONET standards, which were developed for use in North America. See SONET for a full explanation.

Synchronous Idle Character

A transmission control character used in synchronous transmission systems to provide a signal from which synchronism or synchronous correction may be achieved between data terminal equipment, particularly when no other character is being transmitted.

Synchronous Network

A network in which all the communication links are synchronized to a common clock.

Synchronous Optical NETwork.


Synchronous Orbit

An orbit, any point on which has a period equal to the average rotational period of the Earth. If the orbit is also circular and equatorial, it is called a stationary (geostationary) orbit. See also LEO.

Synchronous Payload Envelope

The major portion of the SONET frame format used to carry the STS-1 signal divided into an information payload section and a transport overhead system. SPE is used to address three payload structures: direct to STS- 1 line rate multiplexing; asynchronous DS-3 multiplexing; and synchronous DS-3 multiplexing.

Synchronous Request

An SCSA definition. A request where the client blocks until the completion of the request. Contrast with asynchronous request .

Synchronous Satellite

A satellite in a synchronous orbit. See Synchronous Orbit.

Synchronous TDM

A multiplexing scheme in which timing is obtained from a clock that in turn controls both the multiplexer and the channel source.

Synchronous Time-Division Multiplexing

STDM. A time-division multiplexing method whereby devices have access to a high-speed transmission medium at fixed time periods independent of likely load.

Synchronous Transfer Mode

A proposed transport level, a time division multiplex-and-switching technique to be used across the user's network interface for a broadband ISDN. See STM.

Synchronous Transmission

Transmission in which the data characters and bits are transmitted at a fixed rate with the transmitter and receiver synchronized. Synchronous transmission eliminates the need for start and stop bits. See Synchronous and Asynchronous.

Synchronous Transmission Mode

STM. The synchronous transmission capability of a system that is capable of both synchronous and asynchronous capabilities of Broadband Integrated Services Digital Network (B-ISDN) service.

Synchronous Transport Module 1

STM-1. SDH standard for transmission over OC-3 optical fiber at 155.52 Mbps.

Synchronous Transport Signal Level 1

STS-1. The basic signaling rate for a Synchronous Optical Network (SONET) transmission medium. The STS-1 rate is 51.84 Mbps.

Synchronous Transport Signaling Level n

STS-n. A definition of the transmission speed a Synchronous Optical Network (SONET) transmission medium where n is an integer between 1 and 48 and relates to the multiplier to be applied to the basic STS-1 51.8-Mbps transmission speed. STS-48 is 48 times faster than STS-1, with a speed of 2.5 gigabits per second.


Basic element of decoding procedure. Identifies the bits in error.


Synthetic fuels (or "synfuels") are various fossil fuel substitutes including, gasified and liquefied coal, synthetic natural gas, oil shale, tar sands, and fermented bio- mass materials which are increasingly being seen as necessary to extend and improve existing fuel supplies .


The rules of grammar in any language, including computer language. Specifically, it is the set of rules for using a programming language. It is the grammar used in programming statements.

Syntax Error

An error caused by incorrect programming statements according to the rules of the language being used. Sometimes the computer will throw up "SN" to indicate a syntax error.

Synthesized Voice

Human speech approximated by a computer device that concatenates basic speech parts (or phonemes) together. Usually has a metallic, Germanic sound.

Synthetic Leases

Synthetic leases are off-balance -sheet financings that have drawn investor concern in the wake of the collapse of Enron Corp.

Synthetic Operation

Packets sent into the network that appear to be user data traffic but actually measure network performance. Formerly known as a probe. Also referred to as operation.


The process of setting the frequency of one oscillator equal to that of another.

Syntran Synchronous Transmission

A restructured DS-3 signal format for synchronous transmission at the 47.36 megabits per second DS-3 level of the North American Hierarchy.


Acronym for SYStem GENeration.


The SYStem OPerator of a PC-based electronic bulletin board/mail service or online computer service, such as CompuServe or America On Line. SYSOPs (pronounced sisops) typically put computers and modems on phone lines, then published the phone number, then invited people with computers to call them and leave them messages and interesting software programs which they had written. These programs then became "public domain," or freeware. And other callers were invited to download these programs for their own use. Lead Sysops are called Wizops.


System request; the seldom used key used to get attention from another computer.


An organized assembly of equipment, personnel, procedures and other facilities designed to perform a specific function or set of functions.

System Administrator

The person or persons responsible for the administrative and operational functions of a computer and a telecom system that are independent of any particular application. The system Administrator is likely to be a person with the best overview of all the applications. The System Administrator advises application designers about the data that already exists on the various services, makes recommendations about standardizing data definitions across applications, and so on.

System Build

This is the original manufacturer system building that occurs when the order is placed by the buyer with the vendor. The basic configuration is set up to reflect the users needs at that point in time. Thereafter, if any changes occur to reflect changes in the operating environment, the manufacturer must reconfigure the system to reflect this change. There is usually a reprogramming charge and a delay associated with the change.

System Clock

The clock designated as the reference for all clocking in a network of electronic devices such as a multiplexer or transmission facilities management system.

System Common Equipment

The equipment on a premises that provides functions common to terminal devices such as telephones, data terminals, integrated work station terminals, and personal computers. Typically, the system common equipment is the PBX switch, data packet switch, or central host computer. Often called common equipment.

System Connect

The method by which connection is physically made to the cost computer or local area network.

System Control Computer

The computer system used at CATV or MMDS headend for control of numerous technical functions. These functions include subscriber addressing, channel mapping schedules, ad insertion, encryption keys, PPV, and sometimes IPPV.

System Coordinator

This is the title assigned to the person responsible for administration programming and the training of workers on your phone system.

System Disk

A disk that has been formatted as a system disk. MS-DOS system disks have two hidden files and the COMMAND.COM file. You can start the computer using a system disk.

System Fault Tolerance

SFT. The ability of computer to work fully regardless of component failures.

System Feature

A telephone switch feature that is typically available all the users.

System Gain

The amount of free space path loss that a radio can overcome by a combination of enhancing transmitted power and improving receiver sensitivity.

System Message

Messages that are not associated with a mailbox.

System On a Chip

See SOC.

System Redundancy

The duplication of system components to protect against failure. For protection against failure, install redundant cabling, power supplies, disk storage, gateways, routers, network boards, printers, switches and other mission-critical network components.

System Reload

A process allowing stored data to be written from a tape into the system memory. Picture: your telephone system goes dead. For whatever reason it loses all memory of its generic programming and your specific programming (whose extension gets what, etc.). You have to quickly grab the backup (hopefully you have it on tape or magnetic disk) and load it back into your telephone system's memory. This is called system reload. Sometimes it's done automatically. Sometimes you have to do it manually.

System Segment

A conceptual subset of a system, usually referring to one which can be functionally replaced without damaging the capability of the system.

System Service Provider

An SCSA definition. An entity that provides system wide services, such as session management and security, and the allocation and tracking of resources and groups.

System Side

Defines all cabling and connectors from the host computer or local area network to the cross connect field at the distribution frame.

System Speed Dial

Simplified ways of dialing. You do them by dialing several digits. System speed dial numbers can be used by everyone on the phone system ” whether they are on an electronic phone or just a simply single line phone.

System Test

This definition courtesy Steve Gladstone, author, "Testing Computer Telephony Systems": System test is the phase of the product life cycle that examines the entire system as a "whole" to assure it is ready to go to a true alpha or beta test. System testing is also more oriented to inter system functions as opposed to earlier phases. To pass a system test, all features and functions are expected to work correctly (function to specification) in all areas of the system ” features, administration, maintenance, billing, etc. Additionally, the system must function as an "architectural whole," including all hardware and software components. Representative databases must be loaded to simulate site applications. Full load and stress testing is performed. It is in this phase that the bulk of system level testing will take place. System testing has a major focus on external load and other stimuli.

System V Interface Definition

SVID. A UNIX application-to-system software interface developed and supported by AT&T. The interface is similar to POSIX.

Systems Analysis

Analyzing an organization's activities to figure the best way of applying computer systems to its organization.

Systems Analyst

A person who performs systems analysis and who follows through with methods , techniques and programs to meet the need.

Systems Integrator

A systems integrator is a company that specializes in planning, coordinating, scheduling, testing, improving and sometimes maintaining a computing operation (sometimes companywide , sometimes just locally). In the old days, this was done almost exclusively by the International Business Machines Corporation. Somewhere along, companies discovered they could get more flexibility and computing power at a lower cost by shopping around. Today, hundreds of companies contribute various components ” hardware, software, wiring, communications and so on ” to a company's computer operation. But the added flexibility can bring stunning complexity. Systems integrators try to bring order to the disparate suppliers.

Systems Integration Interface

SII. As used in the definition of the proposed multivendor integration architecture sponsored by Nippon Telegraph and Telephone (NTT) of Japan, SII specifies any set of standardized services used to connect computer based-systems.

Systems Network Architecture

SNA. IBM's successful computer network architecture. At one stage the most successful computer network architecture in the world. In the days of mainframe computers, it was as successful in the computer networking world as AT&T's telephone network design was in telecommunications. The best explanation we've ever read of SNA is in James Harry Green's Dow Jones-Irwin Handbook of Telecommunications. Here is an excerpt:

"SNA is a tree-structured architecture, with a mainframe host computer acting as the network control center. The boundaries described by the host computer, front-end processors, cluster controllers and terminals are referred to as the network's domain. Unlike the switched telephone network that establishes physical paths between terminals for the duration of a session, SNA establishes a logical path between network nodes, and it routes each message with addressing information contained in the protocol. The network is therefore incompatible with any but approved protocols. SNA uses the SDLC data link protocol exclusively. Devices using asynchronous or binary synchronous can access SNA only through protocol converters...SNA works in seven layers roughly analogous to ISO's seven level OSI model. Unlike OSI, however, SNA is fully defined at each level. SNA was first announced in 1974 and is the basis for much of the OSI model, but it differs from OSI in several significant respects." For more on these differences, see page 96 in Green's Handbook.

The following is a description we received from IBM's PR department: "What is SNA?" In general, SNA is the description of the rules that enable IBM's customers to transmit and receive information through their computer networks. SNA may also be viewed as three distinct but related entities: a specification, a plan for structuring a network and a set of products. First, SNA is a specification governing the design of IBM products that are to communicate with one another in a network. It is called an architecture because it specifies the operating relationships of those products as part of system. Second, SNA provides a coherent structure that enables users to establish and manage their networks and, in response to new requirements and technologies, to change or expand them. Third, SNA may be viewed as a set of products: combinations of hardware and programming designed in accordance with the specification of SNA. In addition to a large number of computer terminals for both specific industries and general applications, IBM's SNA product line includes host processors, communication controllers, and adapters, modems and data encryption units. The SNA product line also includes a variety of programs and programming subsystems. Telecommunications access methods, network management programs, distributed applications programming and the network control program are examples.

Systems Network Interconnection

SNI. A service defined by IBM that allows for the interconnection of separately defined and controlled Systems Network Architecture (SNA) networks. See Systems Network Architecture.

Systems Services Control Point

SSCP. An IBM Corp. Systems Network Architecture (SNA) term for the software that manages the available connection services to be used by the Network Control Program (NCP). There is only one SSCP in an SNA network domain, and the software normally resides in the host processor, which is a member of the IBM System/370 mainframe family.

Systems Software

A type of program used to enhance the operating systems and the computer systems they support.


The network management program that purports to let UNIX-based computers be managed along with other IBM systems.

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