Apogee-Audible Indication Control

Apogee -Audible Indication Control


The point on a satellite orbit that is most distant from the center of the gravitational field of the Earth. The point in an orbit at which the satellite is closest to the Earth is known as the perigee. In commercial application, the terms have most significance with respect to LEOs (Low Earth Orbiting) and MEOs (Middle Earth Orbiting) satellite constellations, which travel in elliptical orbits. See LEO and MEO.


To lay the foundation for a future offense.


ATM Passive Optical Network. A passive (i.e., with no repeaters or other active electronics) optical network running ATM. APON is used in the local loop to connect terminal devices to an all optical network running the ATM protocol. See also ATM, Fiber Optics, PON, and SONET.


Additional Point Of Termination. The significance of APOT is that in the CLEC environment APOT is a requirement to submit LSR orders for collocation. These are some requirements that apply to APOT from Bell's point of view: APOT= Location "A" tie down information; CFA= Location "Z" tie down information; ACTL= Location "A" CLLI; LST= Location "Z" CLLI.

Apparent Power

The mathematical product of the RMS current and the RMS voltage. Identical to the VA rating.


Advanced Program-To-Program Communications. In SNA, the architectural component that allows sessions between peer-level application transaction programs. The LUs (Logical Units) that communicate during these sessions are known as LU type 6.2. APPC is an IBM protocol analogous to the OSI model's session layer: it sets up the necessary conditions that enable application programs to send data to each other through the network.


An IBM product that implements APPC on a PC.


Usually refers to a private branch exchange line or extension which is on (i.e. "appears") on a multi-button key telephone. For example, extension 445 appears on three key systems.

Appearance Test Point

The point at which a circuit may be measured by test equipment.


To add the contents of a list, or file, to those of another.


A shortened form of the words APPlications GENerator.

Apple Computer, Inc.

Cupertino, CA. Manufacturer of personal computers. Heavy penetration in the graphics/desktop publishing business and in education. Apple was formed on April Fool's Day, 1976, by Steve Wozniak and Steve Jobs, aided greatly by Mike Markkula.

Apple Desktop Bus

The interface on a Mac where non-peripheral devices, such as the keyboard, attaches. A Mac keyboard or mouse is called an ADB device. Contrast with peripherals, which attach through the SCSI interface. See also USB, which is a new bus for use on PCs but fulfilling essentially the same function as the Apple Desktop Bus.

Apple Desktop Interface

ADI. A set of user -interface guidelines, developed by Apple Computer and published by Addison-Wesley, intended to ensure that the appearance and operation of all Macintosh applications are similar.

Apple Menu

The Apple icon in the upper left hand corner of the Apple Macintosh screen. The Apple menu contains aliases, control panels, the chooser and other desk accessories.

Apple Pie

Both an American icon, and the name chosen for Apple Computer's Personal Interactive Electronics (PIE) division, chartered with extending the company into new growth areas such as Personal Digital Assistants (PDAs), e.g. the Apple Newton. The PIE division includes Apple Online Services, Newton and Telecommunications group , publishing activities, and ScriptX-based multimedia PDA development.

Apple Remote Access

ARA is Apple Computer's dial-in client software for Macintosh users allowing remote access to Apple and third party servers.

Apple URP

Apple Update Routing Protocol. The network routing protocol developed by Apple for use with Appletalk.


Apple Computer's local area network. It uses AppleTalk protocols. AppleShare is Apple system software that allows sharing of files and network services via a file server in the Apple Macintosh environment. See AppleTalk.


Mini-programs that can be downloaded quickly and used by any computer equipped with a Java-capable browser. Applets carry their own software players. See Java.


Apple Computer's proprietary networking protocol for linking Macintosh computers and peripherals, especially printers. This protocol is independent of what network it is layered on. Current implementations exist for LocalTalk (230.4 Kbps) and EtherTalk (10 Mbps).

AppleTalk Address Resolution Protocol


AppleTalk Zone and Device Filtering

Provides an additional level of security for AppleTalk networks. On AppleTalk networks, network managers can selectively hide or show devices and/or zones to ARA clients . See ARA.


See Edge Appliance.


A software program that carries out some useful task. Database managers, spreadsheets, communications packages, graphics programs and word processors are all applications.

Application Based Call Routing

In addition to the traditional methods of routing and tracking calls by trunk and agent group, the latest Automatic Call Distributors route and track calls by application. An application is a type of call, for example, sales or service. Tracking calls in this manner allows accurately reported calls, especially when they are overflowed to different agent groups. See ACD.

Application Binary Interface

ABI. The rules by which software code is written to operate specific computer hardware. Application software, written to conform to an ABI, is able to be run on a wide variety of system platforms that use the computer hardware for which the ABI is designed.

Application Bridge

Aspect Telecommunications' ACD to host computer link. Originally it ran only over R2-232 serial connections, but it now runs over Ethernet, using the TCP/IP link protocol. See also Open Application Interface.

Application Class

An SCSA term . A group of client applications that perform similar services, such as voice messaging or fax-back services.

Application Entity

AE. A cellular radio term. An Application Entity provides the service desired for communication. An Application Entity may exist in an M-ES (Mobile End System) (i.e., mobile application entity) or an F-ES (Fixed End System). An Application Entity is named with an application entity title.

Application Equipment Module

AEM. A Northern Telecom term for a device within the Meridian 1 Universal Equipment Module that supports Meridian Link Modules. The Meridian Link Module (MLM) is an Application Module, specially configured to support the Meridian Link interface to host computers.

Application For Service

A standard telephone company order form that includes pertinent billing, technical and other descriptive information which enables the company to provide communications network service to the customer and its authorized users.

Application Framework

This usually means a class library with a fundamental base class for defining a complete program. The framework provides at least some of the facilities through which a program interfaces with the user, such as menus and windows , in a style that is internally consistent and abstracted from the specific environment for which it has been developed.

This is an explanation I received from Borland. I don't quite understand it, yet. An application framework is an object-oriented class library that integrates user-interface building blocks, fundamental data structures, and support for object-oriented input and output. It defines an application's standard user interface and behavior so that the programmer can concentrate on implementing the specifics of the application. An application framework allows developers to reuse the abstract design of an entire application by modeling each major component of an applications as an abstract class.

Application Gateway

A firewall that applies security mechanisms to specific applications, such as FTP and Telnet servers. An application gateway is very effective but can impose a performance degradation.

Application Generator

AG. A program to generate actual programming code. An applications generator will let you produce software quickly, but it will not allow you the flexibility had you programmed it from scratch. Voice processing "applications generators," despite the name, often do not generate programming code. Instead they are self-contained environments which allow a user to define and execute applications. They are more commonly called applications generator, since one generator can define and execute many applications. See Applications Generator for a longer explanation.

Application Layer

The topmost, visible to the user, presentation of a communications network; the user interface point in network architectures. See Open Systems Interconnection ” Reference Model.

Application Level Firewall

A firewall system in which service is provided by processes that maintain complete TCP connection state and sequencing. Application level firewalls often re-address traffic so that outgoing traffic appears to have originated from the firewall, rather than the internal host.

Application Level proxy

A firewall technology that involves examining application specific data in order to guard against certain types of improper or threatening behaviors.

Application Metering

The process of counting the number of executions of the copies of an application in use on the network at any given time and ensuring that the number does not exceed preset limits. Application metering is usually performed by a network management application running on the file server. Most application metering software will allow only a certain number of copies (usually that number specified in the application software license) of an application to run at any one time and will send a message to any users who try to exceed this limit.

Application Module

A Northern Telecom term for a computer that can be attached to a Northern Telecom phone system and add intelligence and programmability to the phone system. Often, the AM will be a computer conforming to open standards, such as DOS or Windows, or it may be VME-based.

Application Module Link

AML. A Northern Telecom internal and proprietary link that connects the Meridian 1 (via EDSI or MSDL port) to the Meridian Link Module.

Application Program

A computer software program designed for a specific job, such as word processing, accounting, spreadsheet, etc.

Application Program Interface

API. A set of formalized software calls and routines that can be referenced by an application program to access underlying network services.

Application Programming Interface

API. A set of functions and values used by one program to communicate with another program or with an operating system. See API for a better explanation.

Application Profile

As SCSA term. A description of the kinds of resources and services required by a client application (or an application class). An application profile is defined once for an instance of an application; then system services such as the SCR will be able to fulfill the needs of the application without the application having to state its needs explicitly.

Application Server

A dedicated, heavy duty PC which sits on a corporate network and contains a program which people on the network share. Such program would typically be a database ” perhaps a sales force automation program, such as Goldmine, Act or Maximizer. See also Database Server.

Application Service Element

ASE. A messaging term. A module or portion of a protocol in the application layer 7 of the OSI (Open Systems Interconnection) protocol stack. Several ASEs are usually combined to form a complete protocol, e.g., the X.400 P1 protocol which consists of the MTSE (Message Transfer Service Element), and the RTSE (Reliable Transfer Service Element).

Application Service Provider

ASP. The definition of an ASP is evolving. Today it's a company which offers software to business users over the Internet on some sort of per-use charge. For business users, an ASP is a kind of outsourcer; users are not required to buy, own or take care of their own software. Instead of buying software, buying the heavy duty computers to run it on and the heavy duty broadband telecommunications network to get it to all their distant corporate users, the user companies (i.e. the ASP's customers) simply rent the applications from the ASPs, Examples of such applications are ERP (Enterprise Resource Planning), order entry accounting packages, software packages like Microsoft Office, etc.

Application Sharing

Feature of many document-conferencing packages that lets two or more users on different (and usually distant) computers simultaneously use an application that resides on only one of the machines. Imagine, there are three of us and we have to jointly present a PowerPoint presentation to the "big bosses" tomorrow. Today, we have to work on the presentation. But, sadly we're in different cities. So, one of us loads application sharing software and dials the other two in a conference call. That "dialing" may be done over normal phone lines or through the Internet. See NetMeeting, the most popular application sharing.

Application Software Interface

ASI. The Application Software Interface is a product of the Application Software Interface Expert Working Group of the ISDN Implementor's Workshop. The Interface focuses on the definition of a common application interface for accessing and administering ISDN services provided by hardware commonly referred to in the vendor community as Network Adapters (NAs) and responds to the applications requirements generated by the ISDN Users Workshop (IUW). The characteristics of this Application Interface shall be:

  • Portable across the broadest range of system architectures;

  • Extensible (their words, not mine)

  • Abstracted beyond ISDN to facilitate interworking;

  • Defined in terms of services and facilities consistent with OSI layer interface standards.

According to the Application Software Interface Group, the primary goal of the ASI is to provide a consistent set of application software interface services and application software interface implementation agreement(s) in order that an ISDN application may operate across a broad range of ISDN vendor products and platforms. The application software interface implementation agreements will be referenced by (and tested against) the IUW (ISDN Users Workshop) generated applications. It is anticipated that the vendor companies involved in the development of these implementation agreements will build products for the ISDN user marketplace which conform to them. ASI Implementation Agreements are likely to become a US Government Federal Information Processing Standard (FIPS).

Application Specific Integrated Circuit


Applications Engineering

Applications engineering is the process of analyzing your telephone network to find products and services that will reduce your monthly bill without sacrificing network quality. It can be as simple as calling the telephone company to convert a particular service to a Rate Stabilization Plan (RSP). In many instances, the use of applications engineering concepts will increase the quality of your network. For example, putting DIDs onto a T1 will save you money and provide your network with a digital backbone. Unfortunately, most applications engineering is done by the telephone company or by their sales agents . Their main goal is not to save you money, but rather to sell telephone company products. Therefore, they are unlikely to advise you of all the hidden costs of converting to a particular service. A true application engineer will provide you with a complete cost analysis that includes all the conversion costs, and provides you with the "break-even date." The break-even date is the date that your monthly saving offsets the initial conversion cost of the service. It is often used synonymously with the term break- even point.

Applications Generator

An applications generator (AG) is a software tool that, in response to your input, writes code a computer can understand. In simple terms, it is software that writes software. Applications generators have three major benefits:

  1. They save time. You can write software faster.

  2. They are perfect for quickly demonstrating an application.

  3. They can often be used by non-programmers. Applications generators have two disadvantages.

    1. The code they produce is often not as efficient as the code produced by a good programmer.

    2. They are often limited in what they can produce. Applications generators tend to be either general purpose tools or very specific tools, providing support for specific applications, such as connecting voice response units to mainframe databases, voice messaging system development, audiotex system development, etc. There are simple AGs. There are complex AGs. There are general purpose AGs. There are specialized AGs. There are character-based AGs. There are GUI-based AGS. In researching AGs to write computer telephony and interactive voice response applications, I found three different levels of AG packages. First, there are the sort of non-generator generators. They don't really create new software, but they allow you to tweak existing application blocks. There's no compiling and they're pretty simple to use (though they often lack database and host connectivity). Then there are the pretty GUI forms-based app gens. They usually entail building a call-flow picture, using either pretty icons or easy to understand templates. When you're done filling in all the blanks, you compile it and actually "generate" new software. They're very cute. Finally, there's the script level language of a company like Parity Software, San Francisco. Real programmers dig this. They often feel it gives them a lot more power and flexibility. For very complex apps (with T-1/ISDN, ANI, host connection, speech recognition, multimedia capabilities, etc.) you'll probably need the power and flexibility of a script language. Most of the better GUI application generators let you drop down to a script-level language (and C too).

Applications Layer

The seventh and highest layer of the Open Systems Interconnection (OSI) data communications model of the International Standards Organization (ISO). It supplies functions to applications or nodes allowing them to communicate with other applications or nodes. File transfer and electronic mail work at this layer. See OSI Model.

Applications Partner

An Applications Partner is AT&T's new name for an outside company which will write software to work on AT&T phone systems, such as the Merlin, Legend and the Definitely. AT&T is setting up an Applications Partner Program to work with companies to help them develop programs and distribute their products. See also Desktop Connection.

Applications Processor

A special purpose computer which attaches to a telephone system and allows it (and the people using it) to perform different "applications," such as voice mail, electronic mail or packet switching. We think AT&T invented the term. See also Add-On.


Circuit components added to an existing system to provide additional or alternate functions. Some carrier telephone equipment designed for ringdown manual operation can be modified with applique to allow for use between points having dial equipment.


Advanced Peer-to-Peer Networking is, according to its creator IBM, a leading-edge distributed networking feature IBM has added to its Systems Network Architecture (SNA). It provides optimized routing of communications between devices. In addition to simplifying the addition of workstations and systems to a network and enabling users to send data and messages to each other faster, APPN is designed to support efficient and transparent sharing of applications in a distributed computing environment. Because APPN permits direct communication between users anywhere on a network, it facilitates the development of client/server computing, in which workstation users anywhere on a network can share processing power, applications and data without regard to where the information is located. Workstations on an APPN network are dynamically defined so they can be relocated easily on the network without extensive re-programming. APPN also allows remote workstations to communicate with each other, without intervention by a central computer. Also, IBM's Advanced Peer-to-Peer Networking software.

APPN End Node

An APPN end node is the final destination of user data. The end node cannot function as an intermediate node in an APPN network and cannot perform routing functions. See APPN.

Approved Ground

Grounds that meet the requirements of the NEC (National Electrical Code), such as building steel , concrete-encased electrodes, ground rings, and other devices. See AC and Grounding.


A SCSA term. AppServer defines the software environment that enables voice processing applications to run on any computing platform. AppServer sits on a PC equipped with call processing hardware and allows a remotely hosted application to control the call processing hardware.


Annual Percentage Rate. A percentage calculation of a finance charge portion of a financing contact.


Automatic Protection Switching. A means of achieving network resiliency through switching devices which automatically switch from a primary circuit to a secondary (usually geographically diverse) circuit. This switching process would take place when the primary circuit fails or when the error rate on the primary line exceeds a set threshold. There are two basic APS architectures in SONET optical fiber networks: 1+1 and 1:N. A 1+1 architecture is characterized by permanent electrical bridging to service and protection equipment, which is placed at both ends of the circuit. At the head end, or transmitting end, the same payload signal is sent over both the primary and the secondary optical circuit. The optical signal is monitored for failures at the tail end independently and identically over both optical circuits. The receiving equipment at the tail end selects either the service channel (primary circuit) or the protection channel (secondary circuit), based on pre-defined switching performance criteria. A 1:N protection switch architecture is one in which any of "N" (i.e., any Number of) service channels (primary circuits) can be bridged to a single optical protection channel (secondary circuit).


Asia-Pacific Telecommunity.


Automated Quote Contract Billing. System used to price non-tariffed products and services.


  1. Automatic Recall.

  2. Access Registrar. Provides RADIUS services to DOCSIS cable modems for the deployment of high-speed data services in a one-way cable plant requiring telco-return for upstream data.

AR Coating

AntiReflection coating. A thin, dielectric or metallic film applied to an optical fiber surface to reduce its reflection and thereby increase its transmitting ability.


AppleTalk Remote Access. Provides an asynchronous AppleTalk connection to another Macintosh and its network services through a modem. A remote user using ARA can log on to a remote server and mount the volume on his desktop as if he were connected locally.


Attendant Release Loop. A feature of the PBX console. See Release.

Arabic Numerals

Shakespeare was right when he asked, "What's in a name?" The jackrabbit is not a rabbit. It is a hare. A Jerusalem artichoke is not an artichoke; it is a sunflower. Arabic numerals are not Arabic; they were invented in India. India ink (some- times referred to as "Chinese ink") was not known until recently in either China or India.


Arachibutyrophobia is a fear of peanut butter sticking to the roof of your mouth.


Audio grade DRAM. DRAMS are low cost integrated circuits that are widely used in consumer electronic's products to store digital data.


Aramid is a synthetic textile material which is lightweight, nonflammable, and highly impact-resistant. Dupont markets it under the trademark Kevlar. In addition to being used in construction of some fiber optic cables to provide tensile strength, aramid fibers are used in bulletproof vests, sailboat sails, and industrial-strength shoelaces. See Tight Buffer Fiber Optic Cables.

Arbitrated Loop

Arbitrated loop is a shared, 100 MBps (200 MBps full duplex) architecture. Analogous to Token Ring, multiple devices can be attached to the same loop segment, typically via a loop hub. Up to 126 devices and one fabric (switch) attachment are allowed, although the majority of arbitrated loops are deployed with from four to 30 devices. Since the loop is a shared transport medium, devices must arbitrate for access to the loop before sending data. Fibre Channel provides a superset of commands to provide orderly access and ensure data integrity. A GBIC, or gigabit interface converter, is a removable transceiver and is commonly used in Fibre Channel switches, hubs and host bus adapters. A transceiver converts one form of signaling into another, e.g., fiber optic signals to electrical signals.

Arbitrated Loop Topology

A Fibre Channel topology that provides a (FC-AL) low-cost solution to attach multiple communicating ports in a loop. Nodes are linked together in a closed loop. Traffic is managed with a token-acquisition protocol, and only one connection can be maintained within the loop at a time. See Fibre Channel.


The price of gold in London equals the price of gold in New York. If it didn't, traders would step in, simultaneously buy in one place and sell in another, to profit from the discrepancy. This process of buying in one market and selling in another is called arbitrage. It doesn't happen in the world of security exchanges (e.g., stock, bond, currency, and commodities exchanges) much anymore because they all are electronically linked so tightly that they balance in seconds. It does happen in the world of telecommunications. When intraLATA long distance was the sole province of the LECs (Local Exchange Carriers ), for example, you could place a call to gain access to an IXC (IntereXchange Carrier) in order to place an intraLATA call at much lower rates. You weren't supposed to do it, but you could. This was known as arbitrage because you went across the LATA domain, placing an interLATA call to an IXC, and looped right back into the LATA. You profited from that practice, taking advantage of the discrepancy in rates. The IXC also profited, while the LEC lost revenue that rightfully belonged to it, and it alone. The Telecom Act of 1996 put an end to that practice, as the LATA became open to full competition and there no longer was any advantage to arbitrage. Arbitrage remains alive and well for many international long distance routes. As a hypothetical example, it may be much less expensive to call from Sao Paolo to New York via Finland, than to call New York directly. That's also arbitrage, and it exists only because of the artificially high discrepancies in the international long distance tariffs of some carriers and along some specific routes. See also Broker and Tromboning.


A Fibre Channel term. The process of selecting one respondent from a collection of several candidates that request service concurrently.


Attached Resource Computer, the root name of the local area networks (LAN). It was developed by Datapoint Corporation called ARCNET. It was one of the first LANs. Ethernet and Datapoint's incompetent management killed it. See ARCNET.


The word "arcane" was first used in the English language about 1547. It comes from the Latin "arcanus," and means something known or knowable only to those having the key to unlock the secret. We strive to provide you with the keys to unlock the secrets of a wide range of computer and network technologies. We hope that we have been successful. If you think that we have been successful in this endeavor, buy a copy of this book for everyone you know...and for everyone each of them knows . It makes a great gift.


Access Response CHannel. Specified in IS-136, ARCH carries wireless system responses from the cell site to the user terminal equipment. ARCH is a logical subchannel of SPACH (SMS (Short Message Service) point-to-point messaging, Paging, and Access response CHannel), which is a logical channel of the DCCH (Digital Control CHannel), a signaling and control channel which is employed in cellular systems based on TDMA (Time Division Multiple Access). The DCCH operates on a set of frequencies separate from those used to support cellular conversations. See also DCCH, IS-136, SPACH and TDMA.


An Internet term. A corruption of "archive," Archie is a FTP search engine located on several computers around the country. It's sort of a superdirectory to the files on the Internet. If you're looking for a file or even a particular topic, Archie provides its specific location. Veronica, Jughead and WAIS (Wide Area Information Servers) are other tools for searching the huge libraries of information on the Internet. Some companies, such as Hayes, make Archie software which give you a menu driven interface that lets you browse through the various Archie servers on the Internet as though browsing through card catalogs of remote libraries.

Architectural Assemblies

Walls, partitions, or other barriers that are not load bearing. In contrast, Architectural Structures are load bearing .

Architectural Freedom

An AT&T term for flexibility in locating functions, such as control, storage or processing of information, at any site in or around a network, such as customer premises, central offices or regional service bureaus. Architectural freedom also means the ability to distribute functions among combinations of locations and have them interrelate through a high-throughput, low-delay, transparent network. See also Architecture.

Architectural Structures

Walls, floors, floor/ceilings and roof/ceilings that are load bearing. In contrast, Architectural Assemblies are not load bearing.


The architecture of a system refers to how it is designed and how the components of the system are connected to, and operate with, each other. It covers voice, video, data and text. Architecture also includes the ability of the system to carry narrow, medium and broadband signals. It also includes the ability of the system to grow "seamlessly" (i.e. without too many large jumps in price).

Architecture Police

An individual or group within a company that makes sure software and hardware development follows established corporate guidelines. The architecture police tend to rein in creative development efforts.


Readable (and sometimes writable) media. Archival media have defined minimum life- spans over which the information will remain stable (i.e, accurate without degradation).


A backup of a file. An archived file may contain backup copies of programs and files in use or data and materials no longer in use, but perhaps needed for historical or tax purposes. Archive files are kept on paper, on microfilm, on disk, on floppies, etc. They may be kept in compressed or uncompressed form. See Archiver.

Archive Bit

A Windows NT (soon to be Windows 2000) term. Backup programs use the archive bit to mark files after backing them up, using the normal or incremental backup types.

Archive Server

An email-based file transfer facility offered by some computers on Internet.


A software program for compressing files. If you compress files, you will save on communications charges, since you will be able to transmit those files faster as they're now smaller. My favorite MS-DOS archiver, also called file compression utility is Phil Katz's PKZIP.EXE and PKUNZIP.EXE. You can cut a database by as much as 90% and a word processed file by maybe 30% by using PKZIP. How much you can cut is determined by how much fluff is in the file. PKZIP is the most widely-used archive and compression utility today. You can recognized " zipped " files because their extension is always ZIP. There are other compression programs out there which you will recognize by these extensions, ARC, AR7, ARJ, LZH, PAK and ZOO.

Archiving Files

This is a process where the information contained in an active computer file is made ready for storing in a non-active file, perhaps in off-line or near-line storage. Typically when files are archived, they are compressed to reduce their size. To restore the file to its original size requires a process known as unarchiving . See also Archiver.


Attached Resource Computer NETwork. One of the earliest and most popular local area networks. A 2.5M-bits-per-second LAN that uses a modified token-passing protocol. Developed by Datapoint, San Antonio, TX, Arcnet interface cards are now obsolete, having been replaced by faster Ethernet cards (IEEE 802.3) and Token Ring cards (IEEE 802.5).


Automatic Ring Down. A private line connecting a telephone in one location to a distant telephone with automatic two-way signaling. The automatic two-way signaling used on these circuits causes the station instrument on one end of the circuit to ring when the station instrument on the other end goes off-hook. This circuit is sometimes called a "hot- line" because urgent communications are typically associated with this service. ARD circuits are commonly used in the financial industry, but you see them at airports, where they're used to call hotels. May also have one way signaling. Station "A" rings Station "B" when Station "A" goes off hook, but Station "B" cannot ring Station "A".


A public data communications wireless network that allows people carrying hand- held devices to send and receive short data messages. Such messages might be from a sheriff standing in the street searching his department's data base for unpaid parking tickets. ARDIS network was purchased by Motient Corporation, formerly American Mobile, in 1998. The network is the largest packet data network in the US and provides packet data services using the DataTAC protocol. ARDIS was originally jointly owned by Motorola and IBM. It was an outgrowth of a network originally created for IBM service technicians.


All Routes Explorer. An ATM term. A specific frame initiated by a source which is sent on all possible routes in Source Route Bridging.


A logical set of network segments (CLNS-, DECnet-, or OSPF-based) and their attached devices. Areas usually are connected to other areas via routers, making up a single autonomous system.

Area Code

A three-digit code designating a "toll" center in the United States and Canada. Until January, 1995 the first digit of an area code was any number from 2 through 9. The second digit was always a "1" or "0." In January 1995, North America (i.e. the US and Canada) adopted the North American Numbering Plan (NANP) and second digits could be any number. This dramatically increased the number of possible area codes ” from 152 to 792 and the number of phone numbers to more than six billion. For a full explanation, see North American Numbering Plan. For a full listing of area codes, see North American Area Codes.

Area Code Expansion

The new North American Numbering Plan (NANP) allowed basically any three numbers to become an area code. This exploded the number of area codes now possible. Some manufacturers of phone equipment, e.g. Rockwell, choose to call this happening "Area Code Expansion." They claimed that their switch would accommodate all future permutations and combinations of area codes.

Area Code Overlay

See Overlay Area Code.

Area Code Restriction

The ability of the telephone equipment (or its ancillary devices) to selectively deny calls to specific (but not all) area codes. Area code restriction is often confused with "0/1" (zero/one) restriction which denies calls to all area codes by sampling the first and second dialed digits (is it a 0 or 1?) and thus, identifying and blocking an attempt at making a toll call. For a full listing of area codes, see North American Area Codes.

Area Code Split

See Overlay Area Code.

Area Color Code

A cellular radio term. A color code that is shared by all cells controlled through a single Mobile Data Intermediate System (MD-IS). The value of the Area Color Code must be different between any two adjacent cells controlled by adjacent MDISs. Refer to color code.

Area Director

See ADs.

Area Exchange

Geopolitical areas set up for the administration of local telephone services. Usually a single metropolitan area or collection of towns and villages sharing a common area of community interest.

Area Transfer

A rerouting, by splicing, of subscriber cable facilities from one Central office to another, usually within the same exchange area. An area transfer normally requires a change of telephone number for the subscribers involved and is, therefore, scheduled to occur on, or near, the Directory delivery date.

Area Wide Centrex

A centrex service, using the Intelligent Network (IN), to allow centrex service to be provided throughout a large area without dedicated facilities. See Centrex and IN.


  1. A Satellite Term. Alternate Recovery Facility.

  2. Alternative Regulatory Framework.


An argument is an addition or additions to a command that slightly change the command, either by adding options, deleting options and/or specifying filenames. For example, most MS-DOS programs will give you a list of their arguments by typing the name of the .exe and following it with /?, e.g. Type pkunzip /? and you'll get a list of all the arguments that you can follow pkunzip with.

Argument of Perigee

To reach a geostationary orbit, the satellite is first launched on a highly elliptical transfer orbit, the perigee (point closest to the Earth) of which is approximately 200km, allowing it to reach its final altitude at the apogee (furthest point, in this case about 36,000km). The satellite then describes a transfer orbit, which causes it to pass in turn through the perigee and the apogee. The line that passes through the center of the Earth linking the perigee and apogee, known as the line of apsides, itself rotates in the orbital plane at a speed that depends on the geometry of the elliptical orbit and the inclination of the orbital plane to the equator. See Geostationary.

Argument Separator

In spreadsheet programs and programming languages, a comma or other punctuation mark that sets off one argument from another in a command or statement. The argument separator is essential in commands that require more than one argument. Without the separator, the program can't tell one argument from another.


Automatic Room Identification. In Hotel/Motel telephone system applications, the ability to display the room number on the console.


The name of a family of rockets used, amongst other things, for sending communications satellites into space. Ariane is a product of the European Space Agency, the equivalent of the U.S.'s NASA.


American Registry for Internet Numbers. A not-for-profit, voluntary, association charged with the responsibility of management of IP (Internet Protocol) addresses in the geographic areas of North America, South America, the Caribbean, and sub-Saharan Africa. ARIN membership comprises end users, including ISPs (Internet Service Providers), corporate entities, universities, and individuals. ARIN became operational on December 22, 1997 as a result of a broad-based industry agreement to separate management of IP addresses from that of URLs (Uniform Resource Locators). URL administration now is the responsibility of CORE. Both previously were the sole responsibility of InterNIC. ARIN's counterparts are APNIC (Asia Pacific Network Information Center) and RIPE (Reseaux IP Europeens). See also APNIC, CORE , InterNIC, IP, RIPE, and URL.


Aeronautical Radio INC. The collective organization that coordinates the design and management of telecommunications systems for the airline industry. It's one of the largest buyers of telecommunications services and equipment in the world. In its own words, "ARINC develops and operates communications and information processing systems for the aviation and travel industries and provides systems engineering and integration solutions to government and industry. Founded in 1929 to provide reliable and efficient radio communications for the airlines, ARINC is a $280 million company headquartered in Annapolis, MD with over 2,000 employees worldwide." www.arinc.com.

Arithmetic Coding

A compression technique which produces code for an entire message, rather than encoding each character in a message. Arithmetic coding improves on Huffman Encoding, although it is slower. See also Compression and Huffman Encoding.

Arithmetic Logic Unit

ALU. The part of the CPU (Central Processing Unit) that performs the arithmetic and logical operations. See Microprocessor.

Arithmetic Operation

The process that results in a mathematically correct solution during the execution of an arithmetic statement or the evaluation of an arithmetic expression.

Arithmetic Overflow

  1. In a digital computer, the condition that occurs when a calculation produces a result that is greater than a given register or storage location can store or represent.

  2. In a digital computer, the amount that a calculated value is greater than a given register or storage location can store or represent. The overflow may be placed at another location. See Overflow.

Arithmetic Register

A register (i.e. short-term storage location) that holds the operands or the results of operations such as arithmetic operations, logic operations, and shifts.

Arithmetic Shift

A shift applied to the representation of a number in a fixed radix numeration system and in a fixed-point representation system in which only the characters representing the fixed-point part of the number are moved. An arithmetic shift is usually equivalent to multiplying the number by a positive or a negative integral power of the radix, except for the effect of any rounding; compare the logical shift with the arithmetic shift, especially in the case of floating-point representation.

Arithmetic Underflow

In a digital computer, the condition that occurs when a calculation produces a non-zero result that is less than the smallest non-zero quantity that a given register or storage location can store or represent.

Arithmetic Unit

The part of a computing system which contains the circuits that perform the arithmetic operations. See also ALU.


The extension .arj shows that a file or program has been "compressed," and must be "exploded" with the arj program before being either read or used. Groups of files may be compressed together, but this is more commonly done with the zip program. See Zip.


Asynchronous Response Mode. A communication mode involving one primary station and at least one secondary station, where either the primary or one of the secondaries can initiate transmission.

Arm Candy

Colloquial expression for a dumb, but beautiful female date. On your arm, as you arrive at the party, is a gorgeous woman . "My," say your friends , "You have great arm candy." See also Eye and Wrist Candy.

Arm Supplier

A maker of hardware. A term used especially in the gaming business.


The fabled battlefield where God's heavenly forces are to defeat the demon-led forces of evil. The final battle.

Armed Forces Radio Service

AFRS. A radio broadcasting service that is operated by and for the personnel of the armed services. An example of an AFRS is the radio service operated by the U.S. Army for U.S. and allied military personnel on duty in overseas areas.


Automated Management Reporting Information System. Since 1987 the FCC has used the ARMIS system for collecting network infrastructure, financial and operating information from the largest carriers. The FCC produces 10 public reports using this system.


Mechanical protection usually accomplished by a metallic layer of tape, braid or served wires or by a combination of jute, steel tapes or wires applied over a cable sheath for additional protection. It is normally found only over the outer sheath. Armor is used mostly on cables lying on lake or river bottoms or on the shore ends of oceans. See Armored Cable.

Armored Cable

  1. A stainless steel handset cord which is meant to resist vandalism. Typically used on a coin phone, most stainless steel handset cords are too short. This is said to be because they were first ordered for use in prisons, where guards wanted to be certain they would not be used by the prisoners as hanging devices. Thus, they requested Western Electric to make them too short for such a use. Whether there is any validity to this story is dubious. However, it is part of telephone industry folk history and therefore, worth preserving .

  2. In outside cable an armored cable has its sheath covered with three protective layers : a vinyl jacket, a steel wrap, and another vinyl jacket. Armored cable is intended for use in direct- burial applications; the steel armor protects the sheath from damage during installation. See also Hard Cable.


Address Resolution Protocol.

  1. A low-level protocol within the Transmission Control Protocol/Internet Protocol (TCP/IP) suite that "maps" IP addresses to the corresponding Ethernet addresses. In other words, ARP is used to obtain the physical address when only the logical address is known. An ARP request with the IP address is broadcast onto the network. The node on which the IP address resides responds with the hardware address in order that the packets can be transmitted. By way of example, TCP/IP requires ARP for use with Ethernet, in which case the physical address would be defined by the MAC address hard-coded on the NIC (Network Interface Card) of the target workstation. See also RARP.

  2. A low-level protocol which serves to map IP addresses, or other non-ATM addresses, to the corresponding address of the target ATM device. Once the ATM address has been identified, the ARP server can stream data to the target device as long as the session is maintained.


Advanced Research Projects Agency of the U.S. Department of Defense. (The whole DOD annual telecommunications bill exceeds $1 billion.) Much of the country's early work on packet switching was done at ARPA. At one stage it was called DARPA, which stands for Defense Advanced Research Projects Agency. ARPA was the U.S. government agency that funded research and experimentation with the ARPANET and later the Internet. The group within DARPA responsible for the ARPANET is ISTO (Information Systems Techniques Office), formerly IPTO (Information Processing Techniques Office). See also DARPA Internet. DARPA has changed its name to ARPA and back again. It's hard to keep up.


Advanced Research Projects Agency NETwork. A Department of Defense data network, developed by ARPA, which tied together many users and computers in universities, government and businesses. ARPANET was the forerunner of many developments in commercial data communications, including packet switching, which was first tested on a large scale on this network. The predecessor of the Internet, it was started in 1969 with funds from the Defense Department's Advanced Projects Research Agency (ARPA). ARPANET was split into DARPANET (Defense ARPANET) and MILNET (MILitary NETwork) in 1983. ARPANET was officially retired in 1990.


Average Revenue Per Minute.


Average Revenue Per Unit. The average revenue generated per wireless customer unit (e.g., pager or cell phone) per month. ARPU is one indicator of the financial performance of a wireless company or other telecom company, which has lots of subscribers.


Automatic Retransmission reQuest. The standard method of checking transmitted data, used on virtually all high-speed data communications systems. The sender encodes an error-detection field based on the contents of the message. The receiver recalculates the check field and compares it with that received. If they match, an "ACK" (acknowledgment) is transmitted to the sender. If they don't match, a "NAK" (negative acknowledgment) is returned, and the sender retransmits the message. Note: this method of error correction assumes the sender temporarily or permanently stores the data it has sent. Otherwise , it couldn't possibly retransmit the data. No error detection scheme in data transmission is foolproof. This one is no exception.


  1. The description of a location of points by coordinates. A 2-D array is described with x,y coordinates. A 3-D array is described with x,y,z coordinates.

  2. A named, ordered collection of data elements that have identical attributes; or an ordered collection of identical structures.

  3. Two or more hard disks that read and write the same data. In a RAID system, the operating system treats the array as if it were a single hard disk.

  4. A form of telecommunications wireless antenna. See Array Antenna and Phased Array Antenna.

Array Antenna

Take a bunch of directional antennas. Aim them at the same transmitting source. Join them together. Presto, you now have a very powerful giant antenna. Array antennas are used for picking up weak signals. They are often used in astronomical and defense communications systems. For a bigger explanation, see Phased Array Antenna.

Array Connector

A connector for use with ribbon fiber cable that joins 12 fibers simultaneously. A fan-out array design can be used to connect ribbon fiber cables to non- ribbon cables.

Array Processor

A processor capable of executing instructions in which the operands may be arrays rather than data elements.

Array Waveguide

AWG. A passive optical component used for wavelength separation (i.e. to multiplex and de- multiplex wavelengths , particularly those tightly spaced together), which becomes increasingly important in high channel count DWDM systems, which require closer channel spacing. AWGs are fabricated by depositing thin layers of glass onto silicon wafers.

Arrayed Wave Guide

AWG. Chip- sized devices made of glass that combine the streams of different lasers and boost capacity. See also Array Waveguide.


A device used to protect telephone equipment from lightning, electrical storms, etc. An arrestor is typically gas filled so when lightning strikes, the gas ionizes and, bingo, a low resistance to the ground that drains the damaging high voltage elements of the lightning away.

Arrival Rate

A call center term. The pattern in which calls arrive. Call Arrival Rates can be smooth, like outgoing telemarketing calls, or random, like incoming toll-free number calls, or peaked, where calls escalate in response to advertising.


Term coined by the French (who else?) to replace the barbaric English "at" (@) in email addresses. The word is derived from arroba, the Spanish equivalent.


Automatic Route Selection, also called Least Cost Routing. A way that your phone system automatically chooses the least expensive way of making the call that it is presented with. That least expensive way may be a tie line or a WATS line, etc. It may even be dial-up. See Least Cost Routing and Alternate Routing.


Australian Radiocommunications Study Group.


Autorit de R gulation des T l communications (French telecommunications regulator ).


Misinterpreted information from a JPEG or other compressed image. Colour faults or line faults that visibly impact the image negatively. The higher the level of compression, the more likely the artefacting.


An Internet term. An article is a USENET conversation element. It is a computer file that contains a question or piece of information made available to the USENET community by posting to a newsgroup.

Articulation Index

A measure of the intelligibility of voice signals, expressed as a percentage of speech units that are understood by the listener when heard out of context. The articulation index is affected by noise, interference, and distortion.


Distortions in a video signal. Unintended, unwanted visual aberrations in a video image. In all kinds of computer graphics, including any display on a monitor, artifacts are things you don't want to see. They fall into many categories (such as speckles in scanned pictures), but they all have one thing in common: they are chunks of stray pixels that don't belong in the image.

Artificial Intelligence

In 1930s, Alan Turing , a British mathematician , challenged scientists to create a machine that could trick people into thinking it was one of them. The idea is that a computer will have achieved intelligence when a person chatting over a teletype is unable to tell whether a human being or a machine is at the other end of the conversation. And this for long was THE classic definition of artificial intelligence. After half a century, the prospect of passing the Turing test remains so remote that many computer scientists have abandoned it as a practical goal. The real challenge these days with artificial intelligence, now more commonly called "expert systems," is not to recreate people but to recognize the uniqueness of machine intelligence and learn to work with it in intelligent, useful ways.

Artificial Line Interface

In T-1 transmission, refers to the ability of a piece of transmission equipment to attenuate its output level to meet the required loop loss of 15- 22.5 dB normally switch selectable between 0,7.5, and dB.

Artificial Neural Network

ANN. See Neural Network.


Audio Response Unit. A device which gives audible information to someone calling on the phone. "Press 1 for the train timetable to Boston." The ARU reads the timetable. The caller responds to questions by punching buttons on his telephone keypad. If this sounds like Interactive Voice Response ” IVR, you're 100% right because that's exactly what it is. See IVR.


  1. Autonomous System. An Internet term. An Autonomous System is just that ” a system which is autonomous. Typically, an AS is an ISP, an Internet Service Provider. Within the ISP, routers exchange information freely ” all systems are trusted, as they are under a single administration in the same domain. Therefore, such systems can run an IGP (Interior Gateway Protocol) such as IGRP (Interior Gateway Routing Protocol) or OSPF (Open Shortest Path First). As the same level of trust does not exist between ASs, they must run an EGP (Exterior Gateway Protocol) such as BGP (Border Gateway Protocol) or IDRP (InterDomain Routing Protocol). See also BGP, EGP, IDRP, IGP, IGRP and OSPF.

  2. Australian Standards. Standards that have been approved by Standards Australia in response to formal requests from the community, an industry body or government departments.

As Is

A term used in the secondary telecom equipment business. "As is" is equipment that is bought or sold with no stated or implied warranties. You should expect any condition from good to bad, from complete to incomplete. Buy As Is equipment at your own risk.

As Is Tested or As Is Working

A term used in the secondary telecom equipment business. One step up from "as is" condition. The product has been tested. It works and is complete, unless otherwise specified. Buyer should test upon receipt. There is no warranty beyond receipt. Seller is guaranteeing the product will work upon arrival. After that, the buyer is responsible for any problems.


Alarm Surveillance and Control.


IBM's mid-range mini-computer. AS/400 stands for Application System/400. IBM has a product called CallPath/400 which allows AS/400 computers to link to PBXs from the leading manufacturers.


  1. Average Speed of Answer. How long average callers have to wait before they speak to an agent. The time can vary, even over the course of one day, due to call volumes and staff levels. An important measure of service quality. ASA is used in most call centers.

  2. See Affiliated Sales Agency.


Adjunct Switch Application Interface. A software message set or interface protocol on the Lucent (now called Avaya) DEFINITY PBX switch for PBX-to-file server CT (Computer Telephony) applications. ASAI supports activities such as event notification and call control. Essentially, ASAI is a Lucent (now Avaya) specification for SCAI (Switch-to-Computer Applications Interface), an early implementation of CT.


ATM subscriber access multiplexer. A telephone central office multiplexer that supports SDL ports over a wide range of network interfaces. An ASAM sends and receives subscriber data (often Internet services) over existing copper telephone lines, concentrating all traffic onto a single high-speed trunk for transport to the Internet or the enterprise intranet. This device is similar to a DSLAM (different manufacturers use different terms for similar devices).


Autonomous System Boundary Router. ABR located between an OSPF autonomous system and a non-OSPF network. ASBRs run both OSPF and another routing protocol, such as RIP. ASBRs must reside in a nonstub OSPF area. See also ABR, nonstub area, and OSPF.


  1. AIN Switch Capabilities. See AIN.

  2. Abnormal Station Code. Generated by the OCU because of a loss of signal from the DSU/CSU or the DSU/CSU is not attached.

  3. Automatic Slope Control. A device which automatically changes the slope of an amplifier 's curve to compensate for temperature changes.


Association of Communications Enterprises. An association of approximately 750 entrepreneurial communications firms and their suppliers in both the wired and wireless domains. ASCENT was born in 2000 of a name change from Telecommunications Resellers Association (TRA), which was formed in 1992 through the merger of the Telecommunications Marketing Association and the Interexchange Resellers Association. TRA holds several conferences and exhibitions each year, and acts as the resale industry's lobbying group and consumer watchdog. In 1997, TRA absorbed NWRA (National Wireless Resellers Association). www.ascent.org.

ASCI-Assisted Routing

A layer 3 switch that has some of its routing functionality built within ASCIS.


Pronounced: as'-kee. American Standard Code for Information Interchange. It's the most popular coding method used by small computers for converting letters , numbers, punctuation and control codes into digital form. (Computers can only understand zeros or ones.) Once defined, ASCII characters can be recognized and understood by other computers and by communications devices. ASCII defines 128 characters, including alpha characters, numbers, punctuation marks or signals in seven on-off bits and a parity bit (used for data). A capital "C", for example, is 1000011, while a "3" is 0110011. As a seven- bit code, and since each bit can only be a "one" or a "zero," ASCII can represent 128 "things," i.e. 2 x 2 x 2 x 2 x 2 x 2 x 2 which equals 128. ASCII is the code in which virtually every personal computer in the world encodes "things," including IBM, Apple and Radio Shack /Tandy. This compatible encoding (it was developed by ANSI ” the American National Standards Institute) allows virtually all personal computers to talk to each other, if they use a compatible modem, or null modem cable and transmit and receive at the same speed. There are variations of ASCII. (Nothing is totally standard anymore.) The most important variation ” one originally from IBM ” is called Extended ASCII. It codes characters into eight bits (or one byte) and uses those ASCII characters above 127 to represent foreign language letters, and other useful symbols, such as those to draw boxes. But at 127 and below, extended 8-bit ASCII is identical to standard 7-bit ASCII. The ITU (now called the ITU-T) calls ASCII International Telegraph Alphabet 5.

The other major method of encoding is IBM's EBCDIC (pronounced ebb'-si-dick). It's largely used on IBM and IBM-compatible mainframe computers (but not their PCs, which use ASCII and extended ASCII.) EBCDIC is an eight-bit encoding scheme, thus allowing up to 256 "things" to be encoded, i.e. 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 = 256. EBCDIC codes letters, characters and punctuation marks in a totally different way than ASCII. For ASCII files to be read by an IBM mainframe (one that reads EBCDIC), those ASCII files must be translated into EBCDIC by one of the many translation programs available. See also ASCII Editor, Baudot, EBCDIC, Extended ASCII, Extended Graphics Character Set, Morse Code and Unicode.

ASCII Editor

An ASCII editor (also called a "text," "DOS" or "non-document mode" editor) does NOT use extended ASCII and printer [ESCAPE] codes, which are used by word processors to create advanced features such as bold, italic, underlining, and super/subscript printing effects; and fancy formatting such as automatic paragraph reformat , pagination, hyphenation, footers, headers, and margins. I initially wrote this dictionary using an ASCII editor called ZEdit, which is a customized version of QEdit, undoubtedly the best editor ever written. Then, the author QEdit, produced a new and more powerful editor, called The Semware Editor. And I'm now using it to write this edition. Since an ASCII editor can't do so much, why would anyone use one? Well, its strength is in the lack of those very things a word processor has, which clutter it and slow it down! Here are my benefits:

  1. It's lightning fast. No word processor can match an ASCII editor's speed at loading itself, loading files, finding things in files, etc.

  2. A file produced by an ASCII editor can be read and edited by any word processor ( absolutely any). Thus it's the universal word processing file. A WordPerfect file typically can't be read by WordStar and vice versa. The reason is that every word processor uses different high-level codes for the same features (underlining, bolding, etc.) There is no consistency among word processors as to how they encode their text so they can tell printers to do bolding, etc.

  3. An ASCII editor is better to type programming languages, such as EDLIN (for batch files), Basic, FORTRAN, Pascal, etc. If QEdit used extended ASCII and printer codes, it could not be used by these programs...for each program interprets these "high level" codes differently from another program. An ASCII editor types straight, " vanilla " text...nothing fancy about it.


An ASCII file consists solely of ASCII 127 and below ASCII characters that are visible. You create an ASCII file using a simple editor, also called an ASCII editor. An ASCII file is also called a text file. See ASCII.

ASCII-To-Fax Conversion

Allows the transfer of a word-processed file directly to your fax board so it can be faxed without being scanned from a hard copy print-out. Documents faxed with ASCII-to-Fax conversion come out much cleaner at the other end, since the scanning process always degrades the image.


Accunet Spectrum of Digital Services. AT&T's leased line (also called private line) digital service at 56 Kbps. MCI and Sprint have similar services. It is available in N x 56/64 Kbps, for N = 1, 2, 4, 6, 8, 12. The 56/64 Kbps POP-POP service (between long distance carrier central offices) costs the same as an analog line.


A messaging term. Application Service Element. A module or portion of a protocol in the application layer 7 of the OSI (Open Systems Interconnection) protocol stack. Several ASEs are usually combined to form a complete protocol, e.g., the X.400 P1 protocol which consists of the MTSE (Message Transfer Service Element), and the RTSE (Reliable Transfer Service Element).


Access Service Group. Generally represents the tandem or the dial tone office and associated offices subtending a tandem.


Ardire-Stratigakis-Hayduk, a synchronous compression algorithm that is said to offer four times throughput on a typical synchronous channel. It can be used in bridges, routers, ISDN and modems. Transcend of Cleveland, OH said at one point that it was the exclusive licensor of ASH.


  1. Alternate Space Inversion. A line coding technique used on ISDN circuits to communicate from the NI (Network Interface) device to the other CPE. It is the opposite of AMI (Alternate Mark Inversion) which is used frequently at the T-1 level. ASI assigns spaces to binary ones, and alternate polarities (at +/-750 mV) of marks to zeroes. See also AMI.

  2. Advanced Services Implementation.

  3. Application Software Interface. An ISDN term. See Application Software Interface.

  4. Adapter Support Interface. The driver specification developed by IBM for networking over IEEE 802.5 Token-Rings.

Asia-Pacific Telecommunity

APT. A telecommunications organization for the Asia Pacific region.


Application-Specific Integrated Circuit. A silicon chip that is custom-designed for a particular purpose, at least that's the pure definition. In actuality, the term is misleading because many ASICs are designed to perform multiple, generalized tasks . From the manufacturer's point of view, a microprocessor is an ASIC, though they can and are used for widely disparate purposes in the field. An ASIC requires large production volumes to be economical; long design cycles and high-priced design tools (and designers) make them expensive to create, but inexpensive to produce in high-volumes. Manufacturers use ASICs to consolidate many chips into a single package, thereby reducing system board size and power consumption. Many video boards and modems use ASICs. ASICs span programmable array logic (PAL) devices, electrically programmable logic devices (EPLDs), field programmable logic devices (FPGAs), gate arrays, standard cell-based devices, and full custom, designed- from-scratch ICs. See also ASSP, FPGA, and SOC.


Application Specific Integrated Circuit Chip. A fancy name for microprocessor chips which do specific tasks. For example, an ASIC chip might be responsible for a graphics display. See ASIC.


Adaptive Speed Leveling. A US Robotics term for adjusting the transmission speed of a modem up or down, depending on the conditions on the line. US Robotics says it can adjust speed in 2 or 3 seconds after detecting changed line conditions. It requires like modems on either end of the transmission.


See Authenticated SMTP.


  1. Abstract Syntax Notation One. LAN "grammar," with rules and symbols, that is used to describe and define protocols and programming languages. ASN.1 is the OSI standard language to describe data types. The Abstract Syntax Notation is a formal language defined by ITU X.208 and ISO 8824. Under both CMIP and SNMP, ASN.1 defines the syntax and format of communication between managed devices and management applications. See CMIP, SNMP. For a fuller definition, see Abstract Syntax Notation One.

ASOC Technology

This definition from Bookham Technology: ASOC technology is the fabrication of integrated optical components from a base material of silicon. Silicon has excellent optical properties including a low optical loss at 1310nm and 1550nm ” the wavelength bands at which to transmit telecommunication signals. Silicon is the world's best known manufacturing material and benefits from the mature manufacturing processes of the microelectronic industry to significantly reduce the complexity of design and manufacture. Manufacturing ASOC devices fundamentally involves the construction of low-loss, single-mode waveguides onto silicon-on-insulator wafers. Library elements, such as couplers and modulators, and hybridized active elements, such as lasers and photodiodes, are combined to provide devices with a wide range of functionality. Consequently compact and versatile integrated optical components can be produced in high volume and at low cost. The flexible nature of ASOC technology means it can also be utilized to provide application specific, high functionality, high value devices including Arrayed Waveguide Gratings (AWG) and Variable Optical Attenuators (VOA).


See Access Service Ordering Guidelines.


  1. A Northern Telecom term for Attached Support Processor.

  2. Adjunct Service Point. An intelligent-network feature that resides at the intelligent peripheral equipment and responds to service logic interpreter requests for service processing. See also AIN.

  3. Administrable Service Provider. A SCSA term.

  4. Abstract Service Primitive. An ATM term. An implementation-independent description of an interaction between a service-user and a service-provider at a particular service boundary, as defined by Open Systems Interconnection (OSI).

  5. Application Service Provider. See Application Service Provider.

  6. Active Server Page. See Active Server Page.

  7. AppleTalk Session Protocol. A protocol that uses ATP to provide session establishment, maintenance, and teardown , as well as request sequencing. See also ATP.

  8. Auxiliary signal path. In telecommunications, link between TransPaths that allows them to exchange signaling information that is incompatible with the PSTN backbone network; used to provide feature transparency.

  9. Average Selling Price. You sell a bunch of microprocessors to various people at different prices. Divide the total price by the number you sold and bingo you have the average selling price.

  10. Alternate Service Provider. Another name for a new phone company. See Alternate Service Provider.


What do you get when you moon a chicken? A friend named his company Aspect Communications and was mad as a hatter when I told him I knew where his company's name came from. I meant it as a joke. He took it seriously. So, Jim, you've now made history.

Aspect Ratio

The ratio of width to height of a computer display or TV screen. The aspect ratio of NTSC and PAL TV is four units of width to every three units of height. This is expressed as 4 x 3 aspect ratio. A 35 mm frame measures 12 x 24 mm, which means it has two units of width to one unit of height. It is different in size from a TV screen. This is why the side parts of movies are chopped off on TV. For VGA and Indeo video technology, the aspect ratio is 4:3 yielding today's standard PC screen sizes in pixels of 640 x 480, 1024 x 768, 1280 x 10243, 1600 or 1200 and higher.

Aspherical Surface

Lens surface with more than one radius of curvature, i.e. the surface does not form part of a sphere. The aspherical elements of a lens help compensate for many lens aberrations common in simpler lens designs. Aspherical elements are particularly important for wide-angle lenses, since they are prone to distortion.


Advanced SCSI Programming Interface set. In other words, software primitives and data structures which allow software using the ASPI interface to be SCSI host adapter-independent. SCSI stands for Small Computer System Interface. (Pronounced Scuzzie.) ASPI is software that acts as a liaison between SCSI device drivers (the software that drives the SCSI devices) and the interface card (also known as the host adapter). Whenever a new device is added to a computer system, a software program called a "driver" must tell the computer how to talk to the new device. Instead of forcing vendors to write drivers for every host adapter, ASPI lets them write a driver to ASPI standards, supposedly guaranteeing that the device the driver controls will work with all ASPI-compatible host adapters.

The idea behind ASPI is to create a "black box" software interface - one which allows programmers to create software without having to know anything about the details of the SCSI interface hardware used in your computer. With ASPI, it's possible to write programs that can be used with any SCSI-based device used on a computer system that supports ASPI. While things are not always 100% perfect in all cases, ASPI greatly reduces potential compatibility problems for you, the user.

How does ASPI work? Essentially, there are two parts to an ASPI implementation. First, there's the ASPI "manager" which is a device driver supplied by the hardware manufacturer, and the ASPI software application. It's important to note that without an ASPI manager, ASPI compatibility is not possible. It's the manager that creates the standard ASPI- compatibility layer between the SCSI host adapter hardware and the ASPI-compatibility application. The manager is very hardware-specific, and is almost always supplied by the manufacturer of your SCSI host adapter.


Automated Status Query.


  1. Automatic Speech Recognition. See Speech Recognition.

  2. Automatic Send Receive. A teletype or telex machine manufactured by the old Teletype Corporation. Such a hard-copy terminal, if left on and loaded with paper, will receive incoming messages and print them, even when nobody is present. The machine also can be commanded remotely to send the full contents of its paper tape reader.

    Teletype Corporation's ASR-33 was a very popular minicomputer terminal in the 1970s. They now are considered to be obsolete.

  3. Access Service Request. This is a request that a telephone company gives to another telephone company for any of many kinds of interconnectivity or data sharing needs. These requests can be between local carriers or long distance carriers and can originate with either an incumbent or an alternative company. See Access Service Request for more detail.

  4. Authorized Sales Representative. Many phone companies have programs which allow interconnect or other resellers companies to resell their services ” from simple local lines to T-1 lines. The phone companies often pay these companies a small commission for their sales efforts.

  5. Answer Seizure Ratio. A measurement of the effectiveness of a telecommunications service offering. ASR is the relationship between the number of line seizures and the number of answered (i.e., completed) calls. Did you ever get dial tone, and then a "fast busy" because the destination device is unavailable? That is not good for ASR. Did you ever get dial tone, and then an answered call because the destination device is available? That is good for ASR.

  6. Average Service Rate = Percentage of calls placed that actually complete to terminating end. For instance you might hear a technician say the ASR for India is currently 15%. ASR is a term used frequently in the international arena. For instance the ASR would be much higher for calls from the USA to the United Kingdom than third world countries such as India, Zaire, Vietnam etc.


Software that translates assembly language into machine language ” the code of ones and zeros (1s and and 0s) used by computers. Contrast with compiler, which is used to translate a high-level language, such as C, into assembly language first and then into machine language. Assembler code is a close approximation of machine code. It is difficult to write and different for each processor. See also Assembly language.

Assembly Language

A computer language for writing software. It is a language which is converted by programs called compilers or interpreters into machine language programs which consist of only 1s and 0s and which a computer can understand. Even though an assembly language consists of recognizable mnemonics and meaningful words, it's not easy to program in. It is referred to as a "low-level language". Assembly language programs run faster than high-level language programs, such as Basic, COBOL or FORTRAN, which are much easier to learn and program in. Choosing a programming language is a tradeoff of ease for speed. See also Assembler.


A signal is asserted when it is in the state which is indicated by the name of the signal. Opposite of Negated.

Assertion Language

In the design of semiconductors, assertion languages let engineers check properties during simulation and formal verification of their designs. There has been some effort to standardize assertion languages, in particular in something called OpenVera.

Asset Allocation

The practice of allocating a certain percentage of a portfolio to different types of investments (stocks, bonds , foreign stocks, cash reserves or equivalents, gold, mutual funds, futures , options, etc.).

Asset Sale

An asset sale occurs when you sell the assets of the company, but not the company itself. There are tax advantages to both the buyer and seller from an asset sale, instead of a company sale.


A secret romantic rendezvous. An invitation to an assignation doesn't work if she doesn't know the meaning of the word. Are you listening Jane Laino?

Assigned Cell

An ATM term. Cell that provides a service to an upper layer entity or ATM Layer Management entity (ATM-entity).

Assigned Frequency

The center of the assigned frequency band assigned to a station.

Assigned Frequency Band

The frequency band within which the emission of a station is authorized; the width of the band equals the necessary bandwidth plus twice the absolute value of the frequency tolerance. Where space stations are concerned , the assigned frequency band includes twice the maximum Doppler shift that may occur in relation to any point of the Earth's surface.

Assigned Night Answer

ANA. After business hours or when you place your phone system on "Night Answer," this feature sends calls from specified trunks to designated extensions or departments. You may use this feature to send calls directly to modems, or to emergency numbers, or even to outside home numbers.

Assigned Plant Concept

A pair is dedicated from the central office to the subscriber home and maintained at that address, even when idle. See Reassignment.


A call center term. The process of assigning individual employees to specific schedules in a Master File or Daily Workfile. Master File assignment can be done either manually or automatically (based on employee schedule preference and seniority ). See Assignment Lists.

Assignment Lists

In a non-mechanized line assignment environment in a telephone company, assignment lists of lines and numbers are prepared by the Network Administrator as a means of providing input to the Service Center for service order preparation. The lines and numbers made available for assignment are determined by the guidelines for overall loading plan and load balance objectives. The age of telephone numbers is also a consideration. Also see Intercept Interval.

Assisted Global Positioning System


Assisted GPS



The process by which some people seem to absorb success and advancement by kissing up to the boss rather than working hard or smart.


A verb used in Windows by File Manager. You associate a three character extension with an application. This tells File Manager that, when you click twice on the file, File Manager will know which application to launch. For example, you may tell Windows that the .QXD extension is associated with QuarkXpress. When you click on a QXD file, File Manager will launch Quark and load that particular file.

Associated Common-Channel Signaling

A form of common-channel signaling in which the signaling channel is associated with a specific trunk group and terminates at the same pair of switches as the trunk group. The signal channel is usually transmitted by the same facilities as the trunk group.


A relationship between two connection segments that share a common Leg O (i.e., a common subscriber is in control of connection segments). Definition from Bellcore.

Association Control Service Element

ACSE. The International Standards Organization's Open Systems Interconnect (OSI) application layer services used, for example, in Manufacturing Automation Protocol V3.0 (MAP).

Association of Communications Enterprises


Association of Information Technology Professionals



Application Specific Standard Product. An integrated circuit that performs functions for a single application (e.g., keyboard controller). ASSPs use a standard-cell design approach to reduce chip size, costs and product development time. Think of ASSPs as a simply, cheaper way of building ASICs ” Application Specific Integrated Circuits.

Assurance Level

Probability expressed as a percent. Example: There is 90% Assurance (probability) that the mean holding time on the trunk group is between 168.5 and 191.5 seconds.


  1. Automatic Scheduled Testing. A method of testing switched access service (Feature Groups B, C, and D) where the customer provides remote office test lines and 105 test lines with associated responders or their functions' equivalent; consists of monthly loss and C-message noise tests and annual balance test.

  2. Automatic Spanning Tree. A function that supports the automatic resolution of spanning trees in Source Route Bridging (SRB) networks, providing a single path for spanning explorer frames to traverse from a given node in the network to another. AST is based on the IEEE 802.1 standard. See also IEEE 802.1 and SRB.


Advanced Software Technology and Algorithms. Component of the U.S. Government's HPCC program High Performance Computing and Communications program (HPCC) intended to develop software and algorithms for implementation on high-performance computer and communications systems. See also HPCC.


Asia-Pacific Telecommunity Standardization Program.


To inquire about danger.


American Society for Testing and Materials, a non-profit industry-wide organization which publishes standards, methods of test, recommended practices, definitions and other related material.


Application-Specific Unit.


Alternate Serving Wire Center, when a building or customer is served by two different Central Offices. The one that is not his main central office is called the ASWC. It also means that the customer or building has two different NNXs (i.e. phone numbers). E.g. 691 (18th Street central office) and 240 (West Street central office).


Not symmetric, i.e., unbalanced. An asymmetric telecom channel has more bandwidth (i.e. speed) in one direction than in the other. Its bandwidth is unbalanced. There are reasons for this. Take the Internet. Grabbing stuff from the Internet to your PC needs more bandwidth than sending stuff back from your PC. At least that's one theory. To accommodate this theory, for example, there's ADSL (Asymmetric Digital Subscriber Line). ADSL provides asymmetric bandwidth, as the downstream (from the network to the user premises) bandwidth of as much as 6.144 Mbps, and a return channel (from the user premises to the central office) of something like 608 Kbps. Asymmetric can also refer to the physical topology of the network. For example, a point-to-multipoint circuit might connect one device on the East Coast directly to three devices on the West Coast through the use of a bridge. For example, Miller Freeman might lease a multipoint circuit which connects its New York office to its office in San Francisco. At the San Francisco office is a bridge which has three drops , 1 for the San Francisco office and one for each of its two offices in Menlo Park. All communications between the sites take place through the multidrop bridge. The circuit is asymmetric as it lacks symmetry. There is one site connected on the East Coast and there are three sites connected on the West Coast. Multipoint circuits also are known as multi-drop circuits and fan-tail circuits, as they fan out like the tail of a fish on the distant end. See the next several definitions. See also ADSL, Full Duplex and Symmetric.

Asymmetric Cryptography

A form of cryptography involving the use of two different (yet mathematically related) keys so that a message encrypted with one key can only be decrypted with the other key (and vice versa).

Asymmetric Digital Subscriber Line

See ADSL and Asymmetric Digital Subscriber Line Transceiver.

Asymmetric Digital Subscriber Line Transceiver

A microprocessor chip that is the crux of asymmetric digital subscriber line service. I found the following description of just such a chip in Motorola literature describing their MC145650 144-pin transceiver. "The MC145650 is a single integrated circuit transceiver device for ANSI (American National Standard Institute) T1.413 category 2 ADSL modems, based on the Discrete Multi-Tone (DMT) line code. The category 2 specification requires payload rates of (6.144 Mbps + 640 Kbps) downstream and 640 Kbps upstream, with crosstalk, over carrier serving area (CSA) range loops, and to achieve (1.544 Mbps + 176 Kbps) downstream and 176 Kbps upstream with crosstalk, over selected ANSI integrated services digital network (ISDN) loops. The payload makeup is flexible, thereby allowing multiple data streams to be multiplexed and demultiplexed. The MC145650 is capable of data rates up to 8 Mbps downstream and 1 Mbps bidirectionally; however, actual data rates obtained in any system are dependent on loop length, impairments, and transmitted power. The ADSL and DMT techniques are adaptive, changing system parameters based on loop characteristics in order to optimize the data route."

Asymmetric Encryption

See Public Key Encryption.

Asymmetrical Compression

Techniques where the decompression process is not the reverse of the compression process. Asymmetrical compression is more computer- intensive on the compression side so that the decompression of video images can be easily performed at the desktop or in applications where sophisticated codecs are not cost effective. In short, any compression technique that requires a lot of processing on the compression end, but little processing to decompress the image. Used in CD-ROM creation, where time and costs can be incurred on the production end, but playback must be inexpensive and easy. See ASYN.

Asymmetrical Digital Subscriber Line


Asymmetrical Modem

A type of modem which uses most of the available bandwidth for transmission and only a small part for reception .

Asymmetrical Modulation

A duplex transmission technique which splits the communications channel into one high speed channel and one slower channel. During a call under asymmetrical modulation, the modem with the greatest amount of data to transmit is allocated the high speed channel. The modem with less data is allocated the slow, or back channel. The modems dynamically reverse the channels during a call if the volume of data transfer changes.

Asymmetrical Multiprocessing

A relatively simple implementation of multiprocessing in which the operating system kernel runs on one dedicated CPU and assigns tasks as they come in to other "slave processors." It is also known as "master/slave" processing. Compare to Symmetric Multiprocessing.

Asymmetrical PVC

Refers to a PVC (Private Virtual Circuit) which supports simplex, or asymmetrical, assignments of committed information rate in each direction of transmission. A PVC transmission path is duplex, meaning that there must be a communications path in each direction between the two points being connected. However with an transmission which allows characters to be sent at irregular intervals by preceding each character with a start bit, and following it with a stop bit. It is the method most small computers (especially PCs) use to communicate with each other and with mainframes today. In every form of data transmission, every letter, number or punctuation mark is transmitted digitally as "ons" or "offs." These characters are also represented as "zeros" and "ones" (See ASCII). The problem in data transmission is to define when the letter, the number or the punctuation mark begins. Without knowing when it begins, the receiving computer or terminal won't be able to figure out what the transmission means.

click to expand

One way to do this is by using some form of clocking signal. At a precise time, the transmission starts, etc. This is called synchronous transmission. In asynchronous transmission there's no clocking signal. The receiving terminal or computer knows what's what because each letter, number or punctuation mark begins with a start bit and ends with a stop bit. Transmission of data is called synchronous if the exact sending or receiving of each bit is determined before it is transmitted or received. It is called asynchronous if the timing of the transmission is not determined by the timing of a previous character.

Asynchronous is used in lower speed transmission and by less expensive computer transmission systems. Large systems and computer networks typically use more sophisticated methods of transmission, such as synchronous or bisynchronous, because of the large overhead penalty of 20% in asynchronous transmission. This is caused by adding one start bit and one stop bit to an eight bit word ” thus 2 bits out of ten.

The second problem with large transfers is error checking. The user sitting in front of his own screen checks his asynchronous transmission by looking at the screen and re-typing his mistakes. This is impractical for transferring long files at high speed if there is not a person in attendance.

In synchronous transmission start and stop bits are not used. According to the book Understanding Data Communications, characters are sent in groups called blocks with special synchronization characters placed at the beginning of the block and within it to ensure that enough 0 to 1 or 1 to 0 transitions occur for the receiver clock to remain accurate. Error checking is done automatically on the entire block. If any errors occur, then the entire block is retransmitted. This technique also carries an overhead penalty (nothing is free), but the overhead is far less than 20% for blocks of more than a few dozen characters.


  1. Access Tandem.

  2. Advanced Technology. Refers to a 16 bit Personal Computer architecture using the 80X86 processor family which formed the basis for the ISA Bus as found in the first IBM PC.

  3. AudioTex. See AudioTex.

  4. See AT Command Set.

AT Bus

The electrical channel used by the IBM AT and compatible computers to connect the computer's motherboard and peripheral devices, such as memory boards, video controllers, PC card modems, bus mouse boards, hard and floppy disk controllers and serial/parallel input/output devices. The AT bus supports 16 bits of data in one slug, whereas the original IBM PC supported only 8 bits (and was called the ISA bus for Industry Standard Architecture). These days there are much faster "buses," including the EISA, MCA (MicroChannel Architecture), Local Bus, PCI, VESA, etc.

AT Command Set

Also known as the Hayes Standard AT Command Set. A language that enables PC communications software to get an asynchronous and "Hayes-compatible modem" to do what you want it to do. So called "AT" because all the commands begin with "AT," which is short for ATtention. The most common commands include ATDT (touchtone a number), ATA (manually answer the phone), ATZ (reset modem ” it will answer OK), ATSO=O (disable auto-answer), and ATH (hang up the phone).

To avoid having yourself knocked off your data call by the beep that comes in on the phone company's call waiting, put the following line in your modem setup: ATS10=20. That will increase your S10 register to two seconds. This register sets the time between loss of carrier (caused by the 1.5 second call waiting signal) and internal modem disconnect. Factory default on most modems is 1.4 seconds ” just perfect to be cut off by the call waiting tone! (Dumb.)

If you have to dial through several phone systems, waiting for dial tone on the way asymmetrical PVC, the network capacity in each direction does not necessarily have to be equal.


Greek prefix meaning "not together." See Asynchronous Transmission.


See Asynchronous Transmission.

Asynchronous Balanced Mode

ABM. Used in the IBM Token Ring's Logical Link Control (LLC), ABM operates at the SNA data link control and allows devices on a Token Ring to send data link commands at any time and to initiate responses independently.

Asynchronous Completion

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

Asynchronous Device

A device whose internal operations are not synchronized with the timing of any other part of the system.

Asynchronous Gateway

A routing device used for dial-up services such as modem communications.

Asynchronous Mapping

A SONET term. SONET optical fiber transmission systems run at a very high rate of speed, of course. In fact, SONET runs at a minimum of 51.84 Mbps, which is the foundation transmission level known as OC-1 (Optical Carrier Level 1). the OC-1 frame begins as a T-3 electrical signal at 44.736 Mbps. The native format of the incoming signals always is electrical in nature, and originates at various speeds. Examples are 64 Kbps (DS-0), 1.544 Mbps (DS-1 ” specifically, T-1), 2.048 Mbps (DS- 1 ” specifically, E-1), or 44.736 (DS-3 ” specifically , T-3). As these incoming signals of various speeds are presented to the SONET facility, they are multiplexed to form a T-3 frame and are converted from the T-3 electrical format to the OC-1 optical format. The OC- 1 frames then are mapped into (presented to, accepted by, and fit into) the SONET facility in an asynchronous fashion. While the SONET transmission facility, itself, is highly synchronized, it deals with inputs on an asynchronous (start-stop) fashion. These mappings are defined for clear channel transport of digital signals that meet the standard DSX cross connect requirements, typically DS-1 and DS-3 in most practical applications, although DS- 2 is also supported. See also SONET.

Asynchronous Network

A network in which the clocks do not need to be synchronous or mesochronous. Also called a Nonsynchronous Network. See Asynchronous.

Asynchronous Request

An SCSA term. A request where the client does not wait for completion of the request, but does intend to accept results later. Contrast with synchronous request.

Asynchronous Teleconferencing

An interactive group communication that allows individuals to communicate as a group without being present together in time or place. Participants to join and exit the conference when it is convenient for them, leaving messages for others and receiving messages left for them. Computer conferencing is an example of asynchronous teleconferencing.

Asynchronous Terminal

A terminal which uses asynchronous transmissions. See Asynchronous Transmission.

Asynchronous Time Division Multiplexing

A multiplexing technique in which a transmission capability is organized in a priori unassigned time slots. The time slots are assigned to cells upon request of each application's instantaneous real need.

Asynchronous Transfer Mode

ATM is the technology selected by the Consultative Committee on International Telephone & Telegraph (CCITT) International standards organization in 1988 (now called the ITU-T) to realize a Broadband Integrated Services Digital Network (B-ISDN). It is a fast, cell-switched technology based on a fixed- length 53-byte cell. All broadband transmissions (whether audio, data, imaging or video) are divided into a series of cells and routed across an ATM network consisting of links connected by ATM switches. Each ATM link comprises a constant stream of ATM cell slots into which transmissions are placed or left idle, if unused. The most significant benefit of ATM is its uniform handling of services, allowing one network to meet the needs of many broadband services. ATM accomplishes this because its cell-switching technology combines the best advantages of both circuit-switching (for constant bit rate services such as voice and image) and packet-switching (for variable bit rate services such as data and full motion video) technologies. The result is the bandwidth guarantee of circuit switching combined with the high efficiency of packet switching. For a longer explanation, see ATM.

Asynchronous Transmission

Literally, not synchronous. A method of data and/or going through fax/modem switches, you may consider a dial stream that looks like ATDT 1-800-433-9800 [W]212-989-4675 [W]22, where [W] means (in some software programs) "Wait for any key. When you get it, touchtone out the next digits." In other software programs ” pure Hayes command ” W means wait for second dialtone.

If W in square brackets doesn't work for you, then change X3 in your setup line to X1; change your computer's dialed number to 9; and dial your distant computer with your phone. When you hear the modem at the other end answer, tell your computer's software to dial 9. It will dial 9, hear the modem tone at the other end and connect as though it had dialed it all by itself. X1 tells your modem to dial (or touchtone) immediately ” without waiting for dial tone.

You can use several AT commands on one line. You only need AT before the first one. Some modems require commands typed in capital letters. When your dialing fails and you can't figure why, get out of your communications software program and start again. Or in total desperation, turn your computer and modem completely off and start again. The word "Hayes" comes from the manufacturer of modems called Hayes Microcomputer, Norcross, GA, the creator of the command set. Not all Hayes compatible modems are. See also AT+V and Hayes Command Set.

At Local Mode

One of the command modes available on the ISDN set. It is used for compatibility with existing communications packages for analog modems or for data- only application programs. See AT Command Set.

At Work

Microsoft's office equipment architecture announced on June 9, 1993. Microsoft's idea was to put a set of software building blocks into both office machines and PC products, including desktop and network-connected printers; digital monochrome and color copiers; telephones and voice messaging systems; fax machines and PC fax products; handheld systems and hybrid combinations of the above. At Work didn't go very far. But Windows CE came out and became popular.


See AT+V below.


AT&T Corporation - formerly American Telephone and Telegraph Company - was incorporated on March 3, 1885, to manage and expand the burgeoning long-distance business of American Bell Telephone Company and its licensees . It continued as the "long- distance company" until Dec. 30, 1899, when it assumed the business and property of American Bell and became the parent company of the Bell System. It remained the Bell System parent, providing the bulk of telecommunications equipment and services (local, long distance and international) in the United States, until Jan. 1, 1984, when it divested itself of the Bell operating companies that provided local exchange service. On September 20, 1995, AT&T announced that it would be splitting into three companies: a "new" AT&T, to provide communications transmission and switching services; Lucent Technologies, to design, make and sell telecommunications systems and technologies; and NCR Corp., to concentrate on transaction-intensive computing. The strategic restructuring was completed on Dec. 31, 1996. Since then AT&T has made a number of large acquisitions in the wireless, cellular and networking transmission and switching businesses. See also AT&T Consent Decree.

Here is some more AT&T history. In the first part of the 20th century, AT&T, through its Western Electric Company, its manufacturing subsidiary, AT&T affiliated and allied companies around the world manufactured equipment to meet the needs of the world's telephone companies. By 1914, International Western Electric Company locations included Antwerp, London, Berlin, Milan, Paris, Vienna, St. Petersburg, Budapest, Tokyo, Montreal, Buenos Aires, and Sydney. In 1925, Walter Gifford, newly elevated to the presidency of AT&T, decided that AT&T and the Bell System should concentrate on its stated goal of universal telephone service in the United States. He therefore sold the International Western Electric Company to the newly formed International Telephone and Telegraph Company (ITT) for $33 million in 1925, retaining only AT&T's interests in Canada. Although AT&T retreated from international manufacture, it retained an international presence through its drive to provide global telephone service to customers in the U.S.

AT&T engineers first experimentally transmitted the human voice across the Atlantic Ocean via radio in 1915. In 1927 AT&T inaugurated commercial transatlantic telephone service to London using two-way radio. Initially, these calls cost $75 for five minutes. Service spread to other countries, both via London and through direct radio links. Radio- telephone service to Hawaii began in 1931, and to Tokyo in 1934. Telephone service via available radio technology was far from ideal: it was subject to fading and interference, and had strictly limited capacity. In 1956, service to Europe moved to the first transatlantic submarine telephone cable, TAT-1. Transpacific cable service began in 1964.

On January 1, 1984, AT&T started the day a new company. Of the $149.5 billion in assets it had the day before, it retained $34 billion. Of its 1,009,000 employees it retained 373,000. Gone even was the famous Bell logo and name, given under the agreement to the regional telephone companies, excepting only the name's use in Bell Labs. In its place was a stylized globe and the monogram "AT&T." What AT&T had won, its officials believed, was release from former legal shackles, from the increasing conflicts between the way things had been done and a new information age. AT&T now had the freedom to pursue the technology developed at AT&T Bell Laboratories wherever it led; it could compete in the global marketplace.

AT&T Consent Decree

The Telecommunications Act of 1996 defined it as follows: "The term 'AT&T Consent Decree' means the order entered August 24, 1982, in the antitrust action styled United States v. Western Electric, Civil Action No. 82-0192, in the United States District Court for the District of Columbia, and includes any judgment or order with respect to such action entered on or after August 24, 1982. See Telecommunications Act of 1996."


V standards for voice. AT+V is a new ANSI standard for voice modems. It's a superset of the Hayes AT command set which worked so well in modems. AT+V combines prefixed Hayes AT commands with a new set of voice-related +V commands. The specification is detailed in ANSI/TIA/EIA IS-101 "Facsimile Digital Interfaces ” Voice Control Interim Standard for Asynchronous DCE." The TIA TR-29.2 subcommittee details the specification in their PN-3131. Rockwell's voice modem chipset does not comply with this standard, but uses another called AT#V, which is similar. In Windows 95, the variance between these command sets is ratified by the Win 95 system registry and vendor-supplied INF files. See also Windows Telephony.


  1. American Telemarketing Association. The professional industry association for telephone sales and marketing.

  2. Analog Terminal Adapter. A device for a Northern Telecom Norstar phone system that lets it use analog devices, for example fax, answering machines, modems and single line phones, behind the Norstar's central telephone unit (its KSU). Before you buy the analog terminal adapter, check that its speed is fast enough for you. In mid-1995, it was constrained to 9,600 bps, or 14,400 bps if the phone line was clear.

  3. AT Attachment. Refers to the interface and protocol used to access a hard disk on AT compatible computers. Disk drives adhering to the ATA protocol are commonly referred to as IDE interfaced drives for PC compatible computers. The ATA specification is fully backward compatible with the ST-506 standard it superseded. IDE drives are sometimes referred to as ATA drives or AT bus drives. The newer ATA-2 specification defines the EIDE interface, which improves upon the IDE standard. See ATA2, IDE and Enhanced IDE.


The second generation AT attachment specification for IDE devices that defines faster transfer speeds and LBA (Logical Block Address) sector-locating methods. See ATA, IDE and Enhanced IDE.

ATA Document

The latest draft of the ANSI X3.T9 subcommittee AT Attachment document.

ATA Registers

These registers are accessed by a host to implement the ATA protocol for transferring data, control and status information to and from the PC Card. They are defined in the ATA Document. These registers include the Cylinder High, Cylinder Low, Sector Number, Sector Count, DriveHead, Drive Address, Device Control, Error, Feature, Status and Data registers. The I/O and memory address decoding options for these registers are defined within this specification.


Attachment Packet Interface specification does for CD-ROM and tape drives what ATA-2 does for hard drives. It defines device-side characteristics for an IDE-connected peripheral. The benefits of having a single interface for the most common non-disk storage device in the desktop world, the CD-ROM are obvious. For the manufacturer, there is no need to add a separate controller card for the CD-ROM. For the end-user it means no more fussing with interrupts, cards and proprietary driver software. ATAPI essentially adapts the established SCSI command set to the IDE interface.

Atari Jaguar

The world's first 64-bit home console video game system. Made by IBM, the Jaguar was released in 1993, and offered high-speed action, CD-quality sound, and polygon graphics processing beyond most other machines available at the time.


All Trunks Busy. One measure which your phone company or phone systems might give you of telephone traffic in and out of your office. See All Trunks Busy.


  1. Asynchronous Time Division.

  2. ATtention Dial the phone. The first three letters in the most frequently-used command in the Hayes command set for asynchronous modems ” typically those used with microcomputers.


ATtention Dial the phone in touchtone mode. The first four letters in the most frequently-used command in the Hayes command set for asynchronous modems ” typically those used with PCs.


Advanced Technology Demonstration Network. A joint research effort of Bellcore, Bell Atlantic, and the U.S. Government, this network is aimed at demonstrating the efficacy of advanced technologies in the network of the future.


Air-To-Ground. Communications services provided from an airplane in flight. These services have been primarily voice telephone calling services in the past, but are being extended to fax and data services with new digital Air-to-Ground (ATG) systems. ATG services in the U.S. operate in the 800-900 MHz region. In 1994, Ground-to Air services were also introduced. Air-To-Ground service is now available from some planes flying outside the United States.


A non-prophet organization.

Athermal Effect

Any effect of electromagnetic energy absorption not associated with a measurable rise in temperature.


Alliance for Telecommunications Industry Solutions, a trade group based in Washington, D.C. and open to membership of North American and World Zone 1 Caribbean telecommunications carriers, resellers, manufacturers, and providers of enhanced services. Originally called the Exchange Carriers Standards Association (ECSA), ATIS is heavily involved in standards issues including interconnection and interoperability. More recently and in connection with the privatization its Part 68 responsibilities, the FCC selected ATIS and the TIA (Telecommunications Industry Association) as joint sponsors of the Administrative Council for Terminal Attachments (ACTA). ACTA responsibilities include adopting and publishing technical criteria for terminal equipment submitted by ANSI- accredited standards development organizations, and operating and maintaining a database of approved terminal equipment. The first meeting of ACTA was scheduled for May 2, 2001. See also ACTA, Part 68, and TIA. www.atis.org


Automated Telephone Listing Address System.


  1. Automated Teller Machine. The street corner banking machine which is usually hooked up to a central computer through leased local lines and a multiplexed, secure data network. Some ATM networks work over ATM. See 2. America, I believe, is the only place in the world with drive-up ATM machines with Braille lettering.

  2. Asynchronous Transfer Mode. Very high speed transmission technology. ATM is a high bandwidth, low-delay, connection-oriented, packet-like switching and multiplexing technique. Usable capacity is segmented into 53-byte fixed-size cells, consisting of header and information fields, allocated to services on demand. The term "asynchronous" applies, as each cell is presented to the network on a "start-stop" basis ”in other words, asynchronously. The access devices, switches and interlinking transmission facilities, of course, are all highly synchronized.

Here's some history on ATM from the Networking Alliance: The ATM method of moving information is not completely new. Like most things it is an evolution of earlier methods. The key difference between ATM and "X.25 packet switching" and the popular "Frame Relay" technologies is that the packets of the earlier technologies varied in size. Engineers realized that as the speed was dramatically increased to be able to carry "real time" voice and video, the varied length packets would become unmanageable. During the 1980s the ITU, now the ITU-T (International Telecommunications Union-Telecommunications Services Sector), adopted ATM as the transport technology of the future. Ultimately and after a great deal of debate, the ITU-T determined that each cell would be 53 octets long. To meet current and future demands, networking technologies and protocols have evolved to optimize network performance based on traffic characteristics. ATM represents the first worldwide standard to be embraced by the computer, communications and entertainment industries.

Each ATM cell contains a 48-octet payload field, the size of which has an interesting background. Data people prefer to move data in huge blocks or frames, which are more efficient for large file transfers. Voice people, on the other hand prefer tiny blasts of data, which are more effective for moving digitized voice samples (ala PCM in a T-Carrier environment). Since ATM is positioned as the ultimate service offering in support of data , voice data, video data, image data, and multimedia data, the small payload prevailed. With that battle out of the way, the European and U.S. camps clashed, with the European Telecommunications Standards Institute (ETSI) proposing a 32-octet cell and the U.S. Exchange Carriers Standards Association (ECSA) proposing a 64-octet cell ”the issue was the difference in standard PCM voice encoding techniques. After lengthy wrangling, it was decided that a 48-octet cell would be the perfect mathematical compromise. Although neither camp was perfectly pleased (such tends to be the nature of a compromise, I am told), it was a solution that all could accept.

In any event, each cell also is prepended with a 5-octet Header which identifies the Virtual Path (Virtual Circuit), Virtual Channel, payload type, and cell loss priority; as well as providing for flow control, and header error control.

The small, fixed-length cells require lower processing overhead and allow higher transmission speeds than traditional packet switching methods. ATM allocates bandwidth on demand, making it suitable for high-speed connection of voice, data, and video services. ATM services will be available at access speeds up to 622 Mbps, with the backbone carrier networks operating at speeds currently as high as 2.5 Gbps. The ATM edge and core backbone switches operate at very high speeds, and typically contain multiple buses providing aggregate bandwidth of as much as 200+ Gbps. ATM core switches currently are available with capacities of as much as one terabit per second, although none have been deployed at this level.

Here's a full explanation: Conventional networks carry data in a synchronous manner. Because empty slots are circulating even when the link is not needed, network capacity is wasted . The ATM concept which has been developed for use in broadband networks and optical fiber based systems is supported by both ITU-T (nee ITU) and ANSI standards, can also be interfaced to SONET (Synchronous Optical Network). ATM automatically adjusts the network capacity to meet the system needs and can handle data, voice, video and television signals. These are transferred in a sequence of fixed length data units called cells. Common standards definitions are provided for both private and public networks so that ATM systems can be interfaced to either or both. ATM is therefore a wideband, low delay, packet-like switching and multiplexing concept that allows flexible use of the transmission bandwidth and capable of working at data rates as high as 622.08 Mbps, with even higher rates planned. Each data packet consists of five octets of header field plus 48 octets for user data. The header contains data that identifies the related cell, a logical address that identifies the routing, header error correction bits, plus bits for priority handling and network management functions. Error correction applies only to the header as it is assumed that the network medium will not degrade the error rate below an acceptable level. All the cells of a Virtual Path (VP) follow the same path through the network that was determined during call set-up . (Note that ATM is a connection-oriented network service.) As there are no fixed time slots in the system, any user can access the transmission medium whenever an empty cell is available. ATM is capable of operating at bit rates of 155.52 and 622.08 Mbps; the cell stream is continuous and without gaps. The position of the cells associated with a particular VC is random, and depends upon the activity of the network. Cells produced by different streams to the ATM multiplexer are stored in queues awaiting cell assignment. Since a call is accepted only when the necessary bandwidth is available, there is a probability of queue overflow. Cell loss due to this forms one ATM impairment . However, this can be minimized through the use of statistical multiplexers. Bit errors in the header which are beyond the FEC capability can lead to misrouting.

While ATM was developed as a backbone WAN technology, a 25.6 Mbps version of ATM was reluctantly approved by the ATM Forum for use in a LAN workgroup environment. The Desktop ATM25 Alliance, which promoted the standard, disbanded in 1996 due to lack of interest. ATM has continued to march to the desktop, however slowly and at the higher speeds. ATM also has found its way into the LAN world through the development of cost- effective, high-performance ATM LAN backbone switches. PBX manufacturers also are working diligently to determine how best to incorporate ATM switching fabrics into voice/data/video/multimedia PBX systems, resulting in an ATM-based communications controller for premise application. See also ATM Forum, ATM Access Switch and ATM Forum UNI V3.0.


Workgroup ATM running at 25 million bits per second. ATM-25 is mainly used on internal corporate local area networks. For a much fuller explanation, see ATM.

ATM Access Switch

A specialized ATM switch which sits on the end user premise, providing access into a carrier ATM network. The ATM Access Switch is used for such applications as distance learning and telemedicine. It is a high-capacity, cell-based switch designed to support broadband networking. Its fully integrated access, multiplexing and switching functions provide the capability for a variety of combined data, video, imaging and voice services on a single platform. See ATM.

ATM Adaptation Layer

See AAL.

ATM Address

Defined in the UNI Specification as three formats, each having 20 bytes in length including country, area and end-system identifiers. See ATM.

ATM Backbone Switch

A specialized ATM switch which sits in the carrier backbone network. The ATM Backbone Switch is claimed to be ideal for backbone networks supporting multiple services in corporations, telcos, cellular and Internet public service providers. Network operators can aggregate all of their traffic over a single backbone of ATM. It is ideal for service provider backbones supporting multiple services such as cell relay, permanent virtual circuits (PVCs), switched virtual circuits (SVCs) circuit emulation, LAN interconnectivity and frame relay. The Backbone Switch has throughput traffic and traffic management features needed for large-scale ATM deployment and service offerings. ATM backbone switches include internal busses providing bandwidth of as much as 200+ Gbps, and are interconnected by SONET fiber optic transmission facilities currently operating at speeds of as much as 2.5 Gbps. See ATM.

ATM Cell

The ATM term for a set of data. A cell can be a segment (i.e., fragment) of a larger set of data (e.g., a file), or it can be an accumulation of smaller sets of data (e.g., analog voice samples converted into digital bytes through a codec). In its native form, the set of data to be transmitted originates at what is known as the User Layer. As that data enters the ATM network, it is formed into ATM cells by either an ATM switch or an ATM- capable router. Each cell contains a payload (i.e., text field or data field) of 48 octets, with each octet comprising eight bits. Each 48-octet payload is prepended with a header of five octets, which comprises several fields used by the ATM switches to route the data correctly, and to identify the nature of the data in order that the appropriate Quality of Service (QoS) level can be guaranteed . In total, the ATM cell comprises 53 octets. The cells travel through the ATM network in a cell stream. As the cells exit the ATM network, they are reassembled (i.e., reformed) into the native data format in a process known as Segmentation and Reassembly (SAR). See ATM for a more detailed explanation.

click to expand

ATM Distributed Network System

ADNS. A network architecture that essentially spreads intelligence throughout an ATM network, allowing a range of services, including voice, data, and video.

ATM Edge Switch

An ATM cell switch which sits at the edge of the carrier network, providing access from the end users' world to the carriers' ATM backbone network. It is analogous to a Central Office providing access to a Tandem network in the traditional, circuit-switched voice and data world. ATM Edge Switches also are known as Access Nodes and Service Nodes.

ATM Ethernet LAN Service Unit

An ATM ELSU provides 12 independent virtual Ethernet bridges for running over ATM networks. ELSUs are designed for flexible deployment, either local to an ATM switch or at a remote site. ELSUs are designed for LAN internetworking services over ATM networks.

ATM Forum

An industry organization with some 800 members , co-founded by N.E.T. and three other leading networking companies, which focuses on speeding the development, standardization and deployment of ATM (Asynchronous Transfer Mode) products. It has been remarkably successful. The ATM Forum is based in Mountain View, CA. Their phone number is 415-949-6700. See ATM. www.atmforum.com.

ATM Forum UNI V3.0

The ATM Forum UNI V3.0 implementation agreement is based on a subset of the ITU-TS broadband access signaling protocol standards. Additions to this subset have been made where necessary to support early deployment and interoperability of ATM equipment. The procedures and protocol defined in the agreement apply to both public and private UNIs. Moreover, since the protocol is symmetrical, it also applies in the configuration ATM-end-point to ATM-end-point. See ATM and ATM Forum.

ATM Inverse Multiplexing

AIMUX. A device used to combine multiple T-1 or E-1 links into a single broadband facility, over which ATM cells can then be transmitted.

ATM Islands

Local implementations of ATM equipment and applications which are not connected by ATM wide-area services.

ATM Layer

ATM. The second layer of the ATM Protocol Reference Model. At this layer are included such functions as cell multiplexing, creation of headers, flow control and selection of VPIs (Virtual Path Identifiers) and VCIs (Virtual Channel Identifiers). See ATM Layer Link.

ATM Layer Link

A section of an ATM Layer connection between two adjacent active ATM Layer entities (ATM-entities).

click to expand

ATM Link

A virtual path link (VPL) or a virtual channel link (VCL).

ATM Machine

See ATM.

ATM Peer-to-Peer Connection

A virtual channel connection (VCC) or a virtual path connection (VPC).

ATM Protocol Reference Model

A multidimensional protocol model consisting of 4 layers and 3 planes and serving as a point of reference for understanding, developing and implementing ATM technology. Each layer addresses a discrete set of related functions, with all layers closely interrelated. The layers include the Physical Layer, ATM Layer, ATM Adaptation Layer, and Higher Layers related to the specifics of the native user data protocol. The planes include the Control Plane, User Plane and Management Plane.

ATM Switch

A networking device that forwards 53-byte ATM-standard cells between different devices. These switches can be designed for both LAN and WAN environments. An ATM switch acts as both a traffic aggregator, such as when terminating unchannelized DS-3 trunks from DSLAMs, and as a multiservice switch that is capable of forwarding traffic in different ways, depending on what has to be done with it. For example, an ATM switch forwards customer IP traffic directly to an IP network by shunting it to a router or subscriber management system, frame-relay traffic to a frame switch, voice-over-ATM traffic to a voice/data gateway, or long-distance traffic to other central offices via a SONET inter-office ring.

ATM Token Ring LAN Service Unit

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

ATM Traffic Descriptor

A generic list of traffic parameters that can be used to capture the intrinsic traffic characteristics of a requested ATM connection.

ATM User-User Connection

An association established by the ATM Layer to support communication between two or more ATM service users (i.e., between two or more next higher entities or between two or more ATM-entities). The communications over an ATM Layer connection may be either bidirectional or unidirectional. The same Virtual Channel Identifier (VCI) is issued for both directions of a connection at an interface.


ATM Address Resolution Protocol. The means of mapping IETF classical IP addresses to ATM hardware addresses. The process works in much the same way as conventional ARP, which maps network-layer addresses to the MAC (Media Access Control) layer in a LAN.

Atomic Time

See International Atomic Time. See also http://tycho.usno.navy.mil/cgibin/anim.


A feature of a transaction considered or guaranteed to be indivisible. Either the transaction is uninterrupted, or, if it fails, a mechanism is provided that ensures the return of the system to its state prior to initiation of the transaction.


  1. AppleTalk Transaction Protocol. Transport-level protocol that provides a loss-free transaction service between sockets. This service allows exchanges between two socket clients in which one client requests the other to perform a particular task and to report the results; ATP binds the request and response together to ensure the reliable exchange of request-response pairs.

  2. ALPS Tunneling Protocol. A protocol used to transport ALPS data across a TCP/IP network between an ALC/UTS router and an AX.25/EMTOX router. It consists of a set of messages (or primitives) to activate and deactivate ALPS ATP circuits and to pass data.


  1. Abstract Test Suite: A set of abstract test cases for testing a particular protocol. An "executable" test suite may be derived from an abstract test suite.

  2. Actual Transfer Switch ” used in AC power to a telecom site. The AC power comes from the utility to the ATS which routes the power to a main AC breaker.


  1. Advanced Television Systems Committee. Formed by the Joint Committee on Inter-Society Coordination (JCIC) to establish voluntary standards for Advanced TV (ATV) systems, the ATSC focuses on digital television, interactive systems and broadband multimedia communications standards. Membership is open to American (North and South America, including the Caribbean) entities directly affected by the work of the committee. ATSC comprises 54 members including television networks, motion picture and television program producers , trade associations, television and other electronic equipment manufacturers and segments of the academic community. ATSC's proposal for ATV (Advanced TV) was accepted by the FCC on November 28, 1995 and was formally adopted, in the most part, as the U.S. DTV (Digital TV) standard on December 24, 1996. www.atsc.org. See JCIC, HDTV and ATV.

  2. Australian Telecommunication Standardisation Committee.


  1. See Average Talk Time.

  2. Automatic Toll Ticketing. A system which telephone companies use to automatically keep call detail records including calling number, number called, time of day and length of call. The phone company uses this information, together with the cost of phone calls, to generate an invoice to its customers.


A command that assigns a connection number to a workstation and attaches the workstation to the LOGIN directory on the default (or specified) file server. As many as 100 workstations can be attached to a file server running NetWare v2.2. When loaded the NetWare shell (workstation file NETx.COM) automatically attaches your workstation to the nearest file server. You can also specify in SHELL.CFG which server you prefer to attach to.

Attach Terminal

To assign a terminal for exclusive use by the application program. Contrast with Detach Terminal.

Attached Resource Computer Network.

See ARCnet.


An attachment is a file in its native format ” the format it is saved in by its application (e.g. Excel, PowerPoint, Word). An attachment typically accompanies a electronic message. It comes in its native format, i.e. with the extension its application recognizes ” .xls (Excel), .ppt (PowerPoint) or .doc (Word). When you receive an email containing an attachment, Windows gives you two choices ” open it or save it to disk. When you say "open it," Windows looks at the attachment's extension and tries to figure if it has an application on the disk that can open that file. If not, you get an error message. If you opt to save it to disk, you can then change the file's extension and open another program and view the file. One example: If I receive an attachment of a WordPerfect file, I can't open it by clicking on it. But if I save it, then open Word, I can open the file, view it and work with it. In this case I don't have to change the file's extension. Other times, changing the extension works.

Attachment Unit Interface

AUI. In a LAN (Local Area Network), the interface between the medium access unit (MAU) and the data terminal equipment within a data station.


An attempt to circumvent the security measures in place on a network either to gain unauthorized access to the system or to force a denial of service.

Attack Time

The time interval between the instant that a signal at the input of a device or circuit exceeds the activation threshold of the device or circuit, and the instant that the device or circuit reacts in a specified manner, or to a specified degree, to the input. The term often implies a protective action such as the provided by a clipper (peak limiter) or compressor, but may be used to describe the action of a device such as a vox (Voice Operated circuit), where the action is not protective.


Trying to make a telephone call. Also defined as a call offered to a telecommunications system, regardless of whether it is completed. More technically, an attempt is a seizure of a component of equipment. Even a momentary off-hook condition of a telephone may cause a seizure (attempt).


The "operator" of a phone system console. Typically, the first person to answer an incoming call. That person usually directs incoming calls to the proper person or department. That person may also assign outgoing lines or trunks to people requesting them. Few companies spend any time training their attendants. They should. There are two types of things attendants should be trained for:

  1. Manners, including the correct way to keep people waiting and to screen incoming calls, and

  2. The structure of the company. If a caller asks for some help, the attendant should know which department or person might be responsible for providing that help. Increasingly in North America, company phone systems are answered by devices called "automated attendants." They allow a caller to punch in the extension he wants or the department he wants. See Automated Attendant.

Attendant Access Loop

A switched circuit that provides an attendant with a manual means for call completion and control. An attendant access loop might be given a specific telephone number.

Attendant Busy Lamp Field

Lamps, lights or LEDs that show whether a PBX or key system extension is busy or not. These days, many attendant busy lamp fields are being incorporated into CRT displays. We hope more will do this as many lamp-based attendant busy lamp fields are difficult to read.

Attendant Call Waiting Indication

An unusual feature on a PBX console. The call waiting button on the attendant console lights to indicate a predetermined number of calls in queue. The light flashes when a second (programmable) threshold is reached.

Attendant Camp-On

If the extension is busy, the attendant or operator can place the call in a queue behind the call already in progress. When the call is over, the "camped-on" call will automatically ring the extension.

Attendant Conference

PBX feature that allows the attendant (or operator) to establish a conference connection between central office trunks and internal phones.

Attendant Console

An attendant console is the larger, specialized telephone set used by the operator or attendant to answer incoming calls and send those calls to the proper extension. Consoles are becoming more sophisticated these days in several ways. Operators need to punch fewer buttons to move calls around, while the information they present to the attendant is more useful for keeping tabs on calls and letting people know what's happening. Many consoles are acquiring TV screens that report the status of each extension, who's speaking, where the call is going, and whether there are problems, such as broken lines or trunks, etc. anywhere on the system. Some of the more modern screens will allow the operator to send messages around the company that can alert someone as to who's calling before he/she picks up the phone. You can also easily program switches through consoles with CRT (also called TV) screens. In the old days you needed to punch in complex codes. Now you can respond to "Yes/No" decisions on a screen with lots of explanatory words and help menus.

Attendant Control of Trunk Group Access

The telephone operator or attendant controls the users' access to trunks for making local and/or long distance calls. This may reduce long distance call abuse.

Attendant Direct Station Select

This feature gives an operator the ability to reach an extension by simply pushing one button. In direct station select, every extension has its own button. Direct Station Select usually comes with some form of Attendant Busy Lamp Field which shows whether the extensions are busy. Some attendants like direct station select. Others don't, preferring to simply punch in 345, instead of hunting for the button which corresponds to extension 345. The best consoles these days are using some form of easy-to-read screen prompts.

Attendant Exclusion

A PBX feature which stops the attendant from listening in on a phone call once she or he has passed the call to the correct extension.

Attendant Forced Release

An attendant-activated (pushbutton) facility that will automatically "disconnect" all parties on a given circuit when that circuit is "entered" by the attendant.

Attendant Incoming Call Control

A PBX feature which diverts incoming trunk calls automatically to a predetermined phone after a predesignated period of time or number of rings.

Attendant Key Pad

Allows the attendant to perform all functions using a standard touch tone key pad on the console or adjacent to it.

Attendant Locked Loop Operation

PBX feature which allows the attendant at a console to retain supervision or recall capability of any particular call which has been processed.

Attendant Lockout

This feature denies an attendant the ability to re-enter a phone call unless specifically recalled by that PBX extension.

Attendant Loop Transfer

Allows the attendant to transfer any call to another attendant.

Attendant Monitor

A special attendant circuit which allows "listening in" on all circuits with the console handset/headset transmitter deactivated.

Attendant Override

A feature that allows an attendant to enter a busy trunk connection and key the trunk number within the PBX. A warning tone will be heard by the connected parties, after which they connected parties and the attendant will be in a three- way connection.

Attendant Position

Where a telephone operator sits to answer calls and send them on to the people in the company. This is usually in front of a telephone system with buttons, toggle switches, etc. that facilitate this process.

Attendant Recall

When a phone call has been transferred to a telephone extension and not answered, this telephone system feature sends the call back to the attendant. Sometimes the call will return to a special part of the attendant console which will indicate to the attendant that it is a "returned" call. It's a good idea to pay attention to the speed of recall back to the operator. People hate to be extended into endless ringing. Think of calling a hotel and how aggravating it is to wait until the call comes back to an operator after she/he extended it to the room...and it rings and rings.

Attendant Recall On Trunk Hold

The system will recall the attendant if a trunk placed on hold is not re-entered within a predetermined time.

Attendant Transfer of Incoming Calls

A PBX and Centrex feature. A telephone extension is talking on a line but that person wants to transfer the call to someone else. The person hits his/her hookswitch a couple of times. (The hookswitch is the toggle switch the handset depresses when you replace it.) This flashing of the hookswitch signals the attendant to join the call. The person asks the attendant "to please transfer this call." The attendant then transfers the call to the new extension. This feature is totally inefficient as it's hard to reach the attendant, who's always busy, etc. All newer phones can transfer both incoming and outgoing calls automatically by just flashing the hookswitch, dialing the extension number and hanging up.


A telephone system having an attendant or receptionist whose primary job is to answer all incoming calls. Many smaller systems, such as key systems, are not centrally "attended." The phone is simply answered by whoever is near. A non-attended phone system should be set up so anyone can answer an incoming call. Some systems, such as most key systems, come this way from the factory. Others, such as PBXs, have to be specially set up. Some systems can be set up so an attendant will get first shot at answering the incoming call, but then, after a couple of rings, anyone else can answer the call (perhaps a loud "night" bell will ring).

Attended Mode

Imagine a communications situation where your computer is connected over a phone line to another user on another computer and you are uploading and downloading files. Attended mode refers to a situation where both users manually enter the commands required to send or receive a file concurrently, usually while conversing over the phone. Compare this to Unattended Mode.

Attention Key

A key or combination of keys on a computer or terminal which signals the main computer to stop its present task and wait for a new command. The ESCape key is often the Attention Key. In Crosstalk, it's Control A.

Attention Management

A new term covering the whole area of push technology at the desktop.

Attention Signal

The attention signal used by AM, FM, and TV broadcast stations to actuate muted receivers for inter-station receipt of emergency cuing announcements and broadcasts involving a range of emergency contingencies posing a threat to the safety of life or property.


To decrease electrical current, voltage or power in communicating channel. Refers to audio, radio or carrier frequencies. See Attenutation.


The decrease in power of a signal, light beam, or lightwave, either absolutely or as a fraction of a reference value. The decrease usually occurs as a result of absorption, reflection, diffusion, scattering, deflection or dispersion from an original level and usually not as a result of geometric spreading, i.e., the inverse square of the distance effect. Optical fibers have been classified as high-loss (over 100 dB/km), medium- loss (20 to 100 dB/km), and low-loss (less than 20 dB/km). In other words, attenuation is the loss of volume during transmission. The received signal is lower in volume than the transmitted signal due to losses in the transmission medium (such as that caused by resistance in the cable). Attenuation is measured in decibels. It is the opposite of Gain. Some electrical components are listed as "with attenuation" which means they will compensate for irregular electrical supply (e.g. surges). See Gain.

Attenuation Coefficient

The rate at which average power decreases with distance.

Attenuation Constant

For a particular propagation mode in an optical fiber, the real part of the axial propagation constant.

Attenuation Equalizer

Any device inserted in a transmission line or amplifier circuit to improve the shape of its frequency response.

Attenuation Limited Operation

The condition in a fiber optic link when operation is limited by the power of the received signal (rather than by bandwidth or distortion).

Attenuation to Crosstalk Ratio

ACR. The difference between attenuation and crosstalk measured in decibels. For a longer explanation, see ACR.


A device to reduce signal amplitude by a known amount without introducing distortion. Attenuators are installed in fiber optic transmission systems to limit the power level received by the photodetector to within the limits of the optical receiver.


Attendant. What else?


Atto means one quintillion, which is 10 to the power of minus 18. See also FEMTO, which is 10 to the power of minus 15. See Femtosecond.


The form of information items provided by the X.500 Directory Service. The directory information base consists of entries, each containing one or more attributes. Each attribute consists of a type identifier together with one or more values. See Attributes.


Information about an MS-DOS or Windows file that indicates whether the file is read-only, hidden, or system, and whether it has been changed since it was last backed up. You can assign attributes to a file using the ATTRIB command. You can identify a file as read-only (meaning others can't change it, but can read it) and/or as a file you want to archive when using the BACKUP, RESTORE, and XCOPY commands. The command to make a file read only is typically

ATTRIB +R filename

By using the ATTRIB command to make a file "read only," you also make it impossible to erase the file from your disk. If you want to remove the "read only" protection, i.e. make the file "read and write," the command is

ATTRIB -R filename


ADSL Transceiver Unit. The ADSL Forum uses terminology for DSL equipment based on the ADSL model for which the Forum was originally created. Thus, the DSL endpoint is known as the ATU-R and the CO unit is known as the ATU-C. These terms have since come to be used for other types of DSL services, like RADSL and SDSL. ATU generally represents xDSL services.


ADSL Transmission Unit-Central Office. Special electronics in support of ADSL (Asymmetrical Digital Subscriber Line) and placed in the carrier's CO. The ATU-C has a matching unit on the subscriber premise in the form of an ATU-R. The two units, in combination, support a high data rate over standard UTP copper cable local loops. See ADSL and ATU-R.


ADSL Transmission Unit-Remote. Special electronics in support of ADSL (Asymmetrical Digital Subscriber Line) and placed at the customer's premise. The ATU-R has a matching unit at the carrier's Central Office in the form of an ATU-C. The two units, in combination, support a high data rate over standard UTP copper cable local loops. See ADSL and ATU-C.


Australian Telecommunications Users Group, based in Milsons Point, Sydney, Australia.


Advanced TV. Refers to any system of distributing television programming that generally results in better video and audio quality than that offered by the NTSC 525-line standard. This group of techniques is based on digital signal processing and transmission. HDTV (High Definition TV) and SDTV (Standard Definition TV) both fall under the definition of ATV. Although ATV systems are collectively considered to offer better quality than the NTSC signal, they can carry multiple pictures of lower-quality and can also support the cancellation of artifacts in ordinary NTSC signals. See also ATVEF, DTV, HDTV, and NTSC.


Advanced Television Enhancement Forum. An industry group dedicated to creating standards for the future combination of Internet content with ordinary broadcast television, using IP, HTML and JavaScript. See ATV.


Audiotex. Interactive voice response systems that deliver information or entertainment to general telephone callers, i.e. anyone with a phone. Audiotex services are typically widely advertised. They include everything from sex to the weather. See also Audiotex.


  1. A UNIX sound file format, i.e. filename.au. When a Sun Microsystems or other UNIX computer makes a sound, it does so in AU file format. And because the Internet is dominated by Unix boxes, you'll find a lot of AU files there. Macintosh and PC browsers are usually able to play AU files. In contrast, a sound file that originated on a PC is likely to be in WAV or MIDI format instead.

  2. Administrative Unit. A SDH term. A element of a SDH frame that contains enough information to the switching and cross-connection of Virtual Channels (VCs). See also SDH and VC.


AuC is also called AC. It stands for Authentication Center. A mobile term. The AuC is a piece of HLR, which is the Home Location Register ” a permanent database used in GSM mobile systems (like those in Europe) to identify a subscriber and to contain subscriber data related to features and services. HLR is used to authenticate the user of mobile station equipment, i.e. a cell phone. The AuC performs secret, mathematical computations to verify the authenticity of the cell phone and thus to allow the user to make a phone call. AuC is no longer strictly coupled with the HLR. IS-41 Rev. C (now ANSI-41) defines the AuC as a stand-alone network element. See also CAVE.


An FCC definition. A procedure for choosing the users of spectrum space. In auction, the federal government treasury receives the profits.

Audible Indication Control

Three fancy words for the ability to turn up or down the bell or beeper on your PBX attendant console.

Newton[ap]s Telecom Dictionary
Newton[ap]s Telecom Dictionary
ISBN: 979387345
Year: 2004
Pages: 133

flylib.com © 2008-2017.
If you may any questions please contact us: flylib@qtcs.net