Term used in G.165, "General Characteristics of International Telephone Connections and International Telephone Circuits: Echo Cancellers." ACOM is the combined loss achieved by the echo canceller, which is the sum of the echo return loss, echo return loss enhancement, and nonlinear processing loss for the call.


A research network in Austria.

Acoustic Connection

A connection to a device or system made by sound waves.

Acoustic Coupler

An acoustic modem. A modem designed to transfer data to the telephone network acoustically (i.e by sound), rather than electronically (i.e. by direct wire connection). An acoustic coupler consists of a pair of rubber cups into which the user places a telephone handset. One cup picks up the telephone's sound output with a microphone which converts it to an analog signal for transmission to the computer at the other end. The other cup receives the computer's (or terminal's) output and converts it from digital to analog and then uses a speaker to convert that signal into sound which was picked up by the phone's mouthpiece. The data communications link is achieved through acoustic (sound) signals rather than through direct electrical connection. It is attached to the computer or data terminal through an RS-232-C connector. To work the acoustic coupler, start the computer's communications program, dial the distant computer on a single line telephone with a normal (e.g. old-fashioned) handset. When the distant computer answers with a higher pitched "carrier tone," you place the telephone handset in the acoustic coupler and transmit and receive data. Since the data is transmitted by sound between the handset and the acoustic coupler (and vice versa), the quality isn't always reliable. You can usually transmit up to 300 baud, which by today's standards, is painfully slow. People use acoustic couplers when they're short of time or cannot physically connect their modem electrically, e.g. they're using a payphone without an RJ-11 jack or can't get to a WiFi hot space.

Acoustic Kitty

During the 1960s, at the height of the Cold War, American and Soviet spies were trying to be creative to get inside information. Recently declassified documents tell the U.S. planned to use a cat named "Acoustic Kitty" to spy on the Russians. It took five years and more than $14.5 million, but the CIA surgically outfitted the cat with a transmitter, turning it into an eavesdropping platform, using the tail as an antenna. The plan was to have the cat stroll near the Kremlin, curl up on a windowsill or park bench for a nice nap and transmit private conversations by Soviet officials. All was ready, and the CIA agents brought the cat to the park, letting him out of the surveillance van so he could become America's newest spy. Technicians stood by their dials and switches, waiting to capture top secret Soviet conversations. The result? The cat, immediately upon being let out of the van, was run over.

Acoustic Model

In automatic speech recognition, an acoustic model models acoustic behavior of words by gluing together models of smaller units, such as phonemes. (Sorry for the definition of the word model with the word model. But it's actually the best way of defining this term. HN)

Acoustic Noise

An undesired audible disturbance in the audio frequency range.

Acoustic Suspension

A loudspeaker system that uses an air-tight sealed enclosure.

Acoustic Wave

A longitudinal wave that:

  1. Consists of a sequence of pressure pulses or elastic displacements of the material, whether gas, liquid, or solid, in which the wave propagates.

  2. In gases, consists of a sequence of compressions (dense gas) and rarefactions (less dense gas) that travel through the gas.

  3. In liquids, consists of a sequence of combined elastic deformation and compression waves that travel though the liquid.

  4. In solids, consists of a sequence of elastic compression and expansion waves that travel though the solid.

The speed of an acoustic wave in a material medium is determined by the temperature, pressure, and elastic properties of the medium. In air, acoustic waves propagate at 332 meters per second (1087 feet per second) at 0 C, at sea level. In air, sound-wave speed increases approximately 0.6 meters per second (2 feet per second) for each kelvin above 0 C. Acoustic waves audible to the normal human ear are called sound waves. See Analog Wave.


That branch of science pertaining to the transmission of sound. The qualities of an enclosed space describing how sound is transmitted, e.g. its clarity. See also Sound.

Acousto- optic

The interactions between acoustic waves and light in a solid medium. Acoustic waves can be made to modulate , deflect, and focus light waves by causing a variation in the refractive index of the medium. See also Fiber Optics.


Activity Concentration Point.


Advanced Configuration and Power Interface. A specification that enables efficient handling of power comsumption by desktop and laptop computers. With ACPI, the operating system can turn off unused peripheral devices such as CD-ROMs or displays. Users control the time a certain device will power up or down, and the level of power consumption targeted by the device when the battery reaches a certain level of discharge . ACPI also has a deep-sleep mode that allows an image file to reload without rebooting the system and launching applications when the computer is powered . See APM and WFM for a fuller explanation.

Acquired Taste

A friend of mine, Nansi Friedman, claims that I (Harry) am an "acquired taste." She says that's a compliment. I'm not so sure. On the other hand, she is not an acquired taste. She's gorgeous and intelligent . She's also a lawyer, drat.


  1. In satellite communications, the process of locking tracking equipment on a signal from a communications satellite.

  2. The process of achieving synchronization.

  3. In servo systems, the process of entering the boundary conditions that will allow the loop to capture the signal and achieve lock-on. See also phase-locked loop.

  4. In mobile, the process by which a Mobile End System (M-ES) locates a Radio Frequency (RF) channel carrying a channel stream, synchronizes to the data transmissions on that channel stream, and determines whether the channel stream is acceptable to the M-ES for network access.

Acquisition and Tracking Orderwire


Acquisition Time

  1. In a communication system, the amount of time required to attain synchronization.

  2. In satellite control communications, the time required for locking tracking equipment on a signal from a communications satellite. See also satellite.


  1. Attenuation to Crosstalk Ratio. One of the factors that limits the distance a signal may be sent through a given medium. ACR is the ratio of the power of the received signal, attenuated by the media, over the power of the NEXT crosstalk from the local transmitter, usually expressed in decibels (dB). To achieve a desired bit error rate (BER), the received signal power must usually be several times larger than the NEXT power or plus several dB. Increasing a marginal ACR may decrease the bit error rate. See also Attenuation, BER, Crosstalk, dB, and NEXT.

  2. Allowed Cell Rate. An ATM term. An ABR service parameter, ACR is the current rate in cells /sec at which a source is allowed to send. ACR is a parameter defined by the ATM Forum for ATM traffic management. ACR varies between the MCR and the PCR, and is dynamically controlled using congestion control mechanisms.


Academic Computing Research Facility Network. A network connecting various research units such as colleges and research and development laboratories in the U.S.


A standardized way of viewing a file without needing the associated software. For example, you run Word or QuarkXPress, make a pretty desktop published document, replete with diagrams, photos and diagrams. Now you want to send the file to someone to view it in all its glory . Simple. Convert the file to an Acrobat file (which has a .PDF extension) and modem it or send it on disk. The receiving person will run an Acrobat viewer program and see your beautiful work. They won't be able to change your work. But they will be able to see it. Acrobat is from Adobe, the Los Altos, CA company which produces PostScript. Acrobat has three benefits: The Acrobat viewing program is free. You can use Acrobat to view virtually any Windows or Apple software created file. Third, an Acrobat file can be up to 75% smaller than the original file in its native form, i.e. the original Word or QuarkXpress file. This saves considerable transmission time. See also PDF, PostScript.


A pronounceable, artificial word formed from the initial letters or groups of letters of words in a set phrase or series of words. Examples of acronyms include WAC from Women's Army Corps, OPEC from Organization of Petroleum Exporting Countries, LORAN from LOng-RAnge Navigation, and COBOL from COmmon Business Oriented Language. That is not the end of the story. There are variations on the theme.

A recursive acronym is one created through a procedure that repeats until a specified or desired result is achieved. A hackish, and especially MIT Massachusetts Institute of Technology tradition, a recursive acronym humorously refers to itself or another acronym, or both. For example, GNU (an operating system) is a recursive acronym for "GNU's Not UNIX," EINE (an editor) for "EINE Is Not Emacs," and ZWEI (an editor) for "ZWEI Was EINE Initially." All of these recursive acronyms are products of MIT.


  1. Asynchronous Communications Server.

  2. Automatic Call Sequencer. A rudimentary automatic call distributor. See Automatic Call Sequencer.

  3. Advanced Communication System. An old name for AT&T's data communications/data processing service, originally known as BDN (Bell Data Network) and later called Net 1000. ACS supported multiprotocol communications, offering protocol translation (much like X.25 packet switching), as well. In late 1986, after 10 years in birth, AT&T quietly buried ACS, which offered too little in the face of what ” by then ” had become cheap, powerful desktop microcomputers and 1200 bps modems priced at less than $200. ACS was depicted in AT&T presentations as a cloud ” user data entered the cloud of the network on the originating end and exited the cloud on the terminating end. What went on in the cloud of the network was obscured from the user. The thinking was that the user needn't be concerned with what went on inside the cloud; rather, that was AT&T's responsibility and concern. This clever conceptual sell was never successful ” it was way too obscure and offered way too little. See also Cloud.

  4. ATM Circuit Steering. A means of routing ATM traffic to test facilities built in the ATM device (e.g., switch, router, or concentrator), as ATM networks have no point of entry for a test device.


Association Control Service Element. An OSI application-layer protocol. The method used in OSI for establishing a connection between two applications.


Applied Computer Telephony is Hewlett-Packard's program that is a strategy and set of open architecture commands and interfaces for integrating voice and database technologies. The idea is that with ACT a call will arrive at the telephone simultaneously with the database record of the caller. And such call and database record can be transferred simultaneously to an expert, a supervisor, etc. ACT works on both HP 3000 and HP 9000 computers. ACT essentially controls the telephone call movement within PBXs it connects to. See also Open Application Interface.


  1. America's Carriers Telecommunications Association, an organization founded in 1985 by 15 small long distance companies wishing to create an association in which the members controlled the direction of the organization. (That's their words.) "The focus established was to provide national representation before legislative and regulatory bodies, while continuing to improve industry business relations." Perhaps ACTA's greatest claim to fame was its 1996 petition to the FCC to outlaw Voice Over the Net (VON). Sprint was among the members which broke ranks over that issue, upon which the FCC so far has declined to act. In December, 1998, ACTA merged into CompTel (Competitive Telecommunications Association). See also CompTel.

  2. Administrative Council for Terminal Attachments. The FCC privatized its Part 68 responsibilities, selecting ATIS (Alliance for Telecommunications Industry Solutions) and the TIA (Telecommunications Industry Association) as joint sponsors of the Part 68 ACTA (Administrative Council for Terminal Attachments). ACTA comprises 18 members, with two each elected from six interest segments, including Local Exchange Carriers (LECs), Interexchange Carriers (IXCs, or IECs), Terminal Equipment Manufacturers, Network Equipment Manufacturers, Testing Laboratories, and Other Interested Parties. "Invited Observers," a non-voting category, will include members approved by the council on a case- by-case basis. 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 ATIS, Part 68 and TIA.


Alliance of Computer-Based Telephony Application Suppliers was a part of the North American Telecommunications Association (NATA), which now has been fully integrated into TIA (Telecommunications Industry Alliance). See TIA.


Attendant Control of Trunk Group Access. A complicated term for a simple concept, namely that your operator completes long distance calls. A primitive form of toll control.


Association of Computer Telephone Integration Users and Suppliers. A British organization, ACTIUS provides an open industry forum for interchange and discussion on Computer Telephone Integration (CTI) between its members. Subscriptions are UK stlg275.00 for full membership and UK stlg150 for corresponding membership. A key aim of ACTIUS is to explain the benefits of CTI applications to the broadest possible range of users. ACTIUS also represents its members' interests on relevant regulatory and standards issues, both in the UK and the EU (European Union) Address: 11 Nicholas Road, Henley- on-Thames, OXON, United Kingdom RG9 1RB. Contact: Brian Robson, Secretary Tel: 011- 44-1491-575295 Fax; 011-44-1491-410201 email

Activated Return Capacity

A cable TV term. The capability of transmitting signals from a subscriber or user premises to the cable headend. The typical information that can be sent back includes the ID number of the cable TV set-top box and what station you are watching. See also Cable Modem.


The process of enabling a subscriber device for network access and privileges on behalf of a registered account. For a cellular phone to be activated, the system must be informed of the combination of telephone number and Electronic Serial Number (ESN). Once this information has been entered, the phone can place and receive calls.

Activation Fee

One-time fee for initial connection to the cellular system. As competition has intensified, so more and more carriers are dropping or severely reducing their activation fees. They do this in order to attract more new subscribers.

Active Attack

An attack on a computer system which either injects false information into the system, or corrupts information already present in the system. An active attack typically happens when many computers are programmed to attempt to access one computer system simultaneously and the attempts are continued relentlessly during the attack. The active attacks we read about tend to be those which happen to famous web sites. See also Denial of Service Attack, Passive Attack, Smurf Attack and Spoofing.

Active Call

  1. A definition used in Call Centers. An active call is when the connection is in any state except Hold, Null, or Queued. In other words, any state during the establishment of the connection and/or call. This also includes the actual establishment of the connection and/or call itself.

  2. A term which Hayes defines in its Hayes ISDN System adapter manual. An active call is a voice call to which you are connected that is not on hold.

Active Campaign

A call center/marketing term. An outbound calling project that is currently running.

Active Channel

An Active Channel is what Microsoft calls a Web site that has been enabled for push delivery to Internet Explorer 4.0 browsers. To create a channel, developers write and upload a CDF (channel definition format) file to their Web site. New content is delivered to users automatically when the site is updated. Developers and subscribers can control the update frequency; which channels, subchannels , and items (sections) are subscribed to; and other channel characteristics. Most Active Channels use dynamic HTML (DHTML) and other effects to spice up content and make it more interactive. See also: channel definition format, DHTM and push.

Active Circuits

An MCI definition. MCI circuits for which are there is a completed "install order" and a "completed date."

Active Components

Active components, which include transistors and diodes, amplify current, convert alternating current (AC) to direct current (DC) and switch electronic signals, etc. Active components belong to a group called discrete components, which perform a single function, e.g. regulate current or switch signals. By contrast, integrated circuits combine the functions of multiple electronic components on one chip. Together, discrete components and integrated circuits are the building blocks of electronic devices. See also Passive Components.

Active Content

Programs typically written in Java, JavaScript, or ActiveX, which are often downloaded and executed in a single step by a web browser; differs from static content, as typified by web pages built using only HTML tags, which offer a consistent, unchanging document.

Active Contract

One you must sign. See Contract.

Active Coupler

A fiber optic coupler that includes a receiver and one or more transmitters. It regenerates (thus "active") input signals and sends them through output fibers, instead of passively dividing input light.

Active Device

Electronic components that require external power to manipulate or react to electronic output. These include transistors, op amps, diodes, cathode ray tubes and ICs. Passive devices include capacitors, resisters and coils (inductors).

Active Directory

A feature of the Windows NT server and first introduced in NT 5.0, which will be called Windows 2000. Think of it as a real-time, super-fast Directory Information service ” like they have when you call 411 or 555-1212 in North America. But instead of being answered by a person, it answers requests for peoples' phone numbers and addresses by sending instant messages back to the PC workstation which is asking the question. Here's a simple example. Imagine you want to call someone in your organization using your IP telephone. Instead of dialing a number as we do today, we dial a person. Our PC talks to the Windows NT server which we've logged onto and says, in essence, "I want to call Helen. Where is she?" It comes back and says this is "Helen's address. Call there." My PC says "thank you" and then dials Helen at that number. It's called "Active" Directory because its address entries change from moment to moment, as Helen moves around. See TAPI 3.0.

Active Discovery Packet

The type of packet used by PPPoE during the discovery stage.

Active Hub

A device used to amplify transmission signals in certain local area network topologies. You can use an active hub to add workstations to a network or to lengthen the cable distance between workstations and the file saver.

Active Laser Medium

Within a laser, active laser medium is the material that emits coherent radiation or exhibits gain as the result of electronic or molecular transitions to a lower energy state or states, from a higher energy state or states to which it had been previously stimulated. Examples of active laser media include certain crystals, gases, glasses , liquids, and semiconductors. See also Laser Medium.

Active Line

A voice or data communications channel currently in use.

Active Link

A logical communications circuit that is established only for the duration of communications. An active line needs a call-setup and call-clearing procedure for every connection.

Active Matrix Liquid Crystal Display

A technique of making liquid crystal displays for computers in which each of the screen's pixels ” the tiny elements that make up a picture ” is controlled by its own transistor. Active matrix LCD display technique uses a transistor for each monochrome or each red, green and blue pixel. It provides sharp contrast, speedier screen refresh and doesn't lose your cursor when you move it fast (also knowing as submarining). Some active matrix CD screens are as fast as normal glass CRTs.

Active Medium

The material in fiber optic transmission, such as crystal, gas, glass, liquid or semiconductor, which actually "lases." It's also called laser medium, lasing medium, or active material.

Active Monitor

Device responsible for managing a Token Ring. A network node is selected to be the active monitor if it has the highest MAC address on the ring. The active monitor is responsible for such management tasks as ensuring that tokens are not lost, or that frames do not circulate indefinitely. See also ring monitor and standby monitor.

Active Open

Used in TCP to request connection with another node.

Active Optical Component

Active optical components are fiber-optic bits and pieces that need power (hence the word "active") to operate and cause electrical signals within a network to create, modulate, or amplify the original light signal. Examples include source lasers, modulators, pump lasers and wavelength lockers. Active Optical Components are used to manufacture, transmit, modulate, and amplify light. Source lasers create the light; modulators (electroabsorption or lithium niobate) are used to encode the optical signal into a stream of on/off bits; and pump lasers emit light to amplify or boost the source signal.

Active Participation

A feature in an automatic call distributor, a piece of equipment used in call centers. This feature is typically used to allow intrusion with the ability to speak and listen by a supervisor into an Agent Call. The resultant call is a conference. A Versit definition.

Active/Passive Device

On a local area network, a device that supplies current for the loop is considered active. Such a device is a Token Ring MAU (Multistation Access Unit). A device, which does not supply current, is considered passive.

Active Pixel Region

On a computer display, the area of the screen used for actual display of pixel information.

Active Push

The server on the Web interacts with the client by sending all the content to the client upon the client's request (polling), essentially the way that a client/server application might. PointCast is an example of this. See Push and Directed Push.

Active Satellite

A satellite carrying a station intended to transmit or retransmit radio communication signals. An active satellite may perform signal processing functions such as amplification, regeneration, frequency translation and link switching, to make the signals suitable for retransmission. See Geosynchronous Satellite.

Active Server Pages

ASP.A specification for a dynamically created Web page with a .ASP extension that utilizes ActiveX scripting ” usually VB Script or Jscript code. When a browser requests an ASP page, the Web server generates a page with HTML code and sends it back to the browser. ASP pages are similar to CGI scripts, but they enable Visual Basic programmers to work with familiar tools.

Active Splicing

Aligning the ends of two optical fibers with the aim of minimizing the splice loss.

Active Star

See Star Coupler and Multiport Repeater.

Active Tag

An RFID tag that comes with a battery that is used to power the microchip's circuitry and transmit a signal to a reader. Active tags can be read from 100 feet or more away, but they're expensive ” more than $20 each in the early part of 2004. They're used for tracking expensive items over long ranges. For instance, the US military uses active tags to track containers of supplies arriving in ports.

Active Terminator

A terminator that can compensate for variations in the terminator power supplied by the host adapter through means of a built-in voltage regulator .

Active Video Lines

All video lines not occurring in the horizontal and vertical blanking intervals. In other words, the lines conveying the video and audio signals.

Active Vocabulary

A phrase used in voice recognition to mean a group of words which a recognizer has been trained to understand and recognize. When a voice says ... PAIR, it knows the word means two, not the fruit, pear. That's one example of why voice recognition is so difficult. English, particularly, is a very complex and confusing language.

Active Window

A Windows term. The active window is the window in which the user is currently working. An active window is typically at the top of the window order and is distinguished by the color of its title bar, typically dark blue.

Active/Passive Device

On a local area network, a device that supplies current for the loop is considered active. Such a device is a Token Ring MAU (Multistation Access Unit). A device which does not supply current is considered passive.


A call center/marketing term. Refers to customers who have purchased within a time period defined by the company instigating the marketing. Customers who have purchased outside the specified time period are considered inactive.


In its simplest terms, said InfoWorld, May 19, 1997, ActiveX is an architecture that lets a program (the ActiveX control) interact with other programs over a network (such as the Internet). It's quite a different animal than Java, which is an entire new programming language plus a specification for a virtual machine. The ActiveX architecture, according to InfoWorld,uses Microsoft's Component Object Model (COM) and Distributed COM (DCOM) standards. COM allows different applications to talk to each other locally. DCOM allows them to talk over a network.

ActiveX, formerly known as Object Linking and Embedding, or OLE, is an umbrella of mechanisms designed to bring sound bytes, animation and interactivity to Web documents, similar to plug-in technology for Netscape Communications Corp.'s Navigator and Sun Microsystems Inc.'s Java applets. They all provide ways to send small programs to a browser, without the involvement of any other special software on the desktop. In short, ActiveX is a software code from Microsoft which allows a developer to add move things to an otherwise static Web page. ActiveX is positioned by Microsoft as a competitive move against Java.

Microsoft's ActiveX enables software components to interact with one another in a networked environment, regardless of the language in which they were created. Kind of like the Olympics. ActiveX is built on the Component Object Model (COM).

Elements of ActiveX are:

  • ActiveX Controls ”the interactive objects in a Web page that provide interactive and user-controllable functions.

  • ActiveX Documents ”enable users to view non-HTML documents, such as Microsoft Excel or Word files, through a Web browser.

  • Active Scripting ”controls the integrated behavior of several ActiveX controls and/or Java Applets from the browser or server.

  • Java Virtual Machine ”the code that enables any ActiveX-supported browser such as Internet Explorer 3.0 to run Java applets and to integrate Java applets with ActiveX controls.

  • ActiveX Server Framework ”provides a number of Web server-based functions such as security, database access, and others.

ActiveX Controls

A component that can be inserted in a page to provide functionality not directly available in HTML, such as animation sequences, credit-card transactions, real-time video sequences or spreadsheet calculations. ActiveX controls can be implemented in a variety of programming languages using C++, Visual Basic or Java. Over 1,000 ActiveX controls are available today. These include the Macromedia Shockwave for Director control and the Adobe Acrobat control.

Activity Concentration Point

ACP. A location on a telecommunications network where there is high communications traffic, including voice, data, document distribution and teleconferencing. Generally, there will be some switching equipment present at the ACP.

Activity Costing

A call center term. The costing methodology used to determine the specific cost of a given activity. (See Cost Per Phone Hour.)

Activity Factor

A decimal fraction which represents the percentage of speech on a voice channel versus those periods of (non-talking) silence on that channel. Most voice channels carry actual speech 30% to 40% of the total available time. This represents an activity factor of 0.3 to 0.4.

Activity Report

A report printed by a facsimile machine which lists all transmissions and receptions ” their time, date, and number of documents; the remote unit type, diagnostic codes; and machine identification.


Access Customer Terminal Location. The CLLI code that identifies the location of the access customer's switch.


  1. Association of Competitive Telecommunications Suppliers. Trade association of telephone equipment dealers in Canada.

  2. Automatic Coin Telephone Service includes a telephone company central office that can complete all types of payphone calls automatically without an operator. Recorded announcements are used to convey instructions to the customer.


Motorized device used to position an earth-bound satellite dish for reception of programs. Actuators are built into a horizon-to-horizon mount; they look like motorized shock absorbers when attached to a polar mount.


Automatic Calling Unit. Also an 801 ACU. A telephone company-provided device instructed by a computer to place a call on behalf of the computer. The call is then connected to a telephone company-provided Data Set. Anyone other than an IBM shop would simply buy a Hayes or Hayes-compatible modem, and not bother with the trouble and expense of an ACU.


The Association for Telecommunications Professionals in Higher Education. Prior to 1998, it was the Association of College & University Telecommunications Administrators. The new name is more meaningful, but the acronym stuck. ACUTA is an international, not-for-profit educational association serving approximately 800 institutions of higher learning. All members are director level or higher, and are responsible for data, video, communications, and all variety of networks, in addition to traditional telephony. Corporate affiliate members are welcome, as well.


Administrative Domain. A group of hosts , routers, and networks operated and managed by a single organization.

Ad Click Rate

Sometimes referred to as "click-through." This is the percentage of ad views that resulted in an ad click.

Ad Clicks

Number of times users click on an ad banner.

Ad Hoc Network

A wireless network comprising only stations without access points.

Ad Insertion Equipment

Tape or solid state equipment for interrupting programming on a specific channel and putting prerecorded advertising on the channel.

Ad Views

Number of times an ad banner is downloaded and presumably seen by visitors . If the same ad appears on multiple pages simultaneously, this statistic may under- state the number of ad impressions, due to browser caching. Corresponds to net impressions in traditional media. There is currently no way of knowing if an ad was actually loaded. Most servers record an ad as served even if it was not.


  1. Average Delay to Abandon. Average time callers are held in queue before they get frustrated and decide to hang up.

  2. A high level computer language which the Department of Defense has been trying to foist on its suppliers and thus, make a standard. Ada is named for British mathematician Ada Lovelace, known at the time as Lady Lovelace. She was the girlfriend of Charles Babbage, the inventor of the computer.


Automatic Directory Assistance Call Completion.


Automatic Dialing and Announcing Device. Device which automatically places calls and connects them to a recording or agent. A Canadian term for an automatic dialer.

Adaptable Digital Filtering

A way of fixing twisted-pair telephone lines so they carry data more efficiently up to 12,000 feet before the need to regenerate the signal. The filter can be customized to meet the needs of a twisted pair.


  1. A device used to connect a terminal to some circuit or channel so it will compatible with the system to which it is attached. An adapter converts one type of jack or plug to another, for example, from old 4-prong telephone jacks to new modular. An adapter may also combine various items, such as putting three plugs in one jack.

  2. Another name for a NIC ” Network Interface Card ” a card which fits into a computer and joins the computer to a local area network.

Adapter Card

A printed circuit card installed inside of a computer. It takes data from memory and transmits it over cable to connected devices such as a modem, or printer.

Adapter Segment

A name sometimes used for the upper memory area of a PC, at hexadecimal addresses A000 through EFFF (640K to 1024K).

Adaptive Algorithm

An algorithm that can "learn" and change its behavior by comparing the results of its actions with the goals that it is designed to achieve.

Adaptive Antenna Array

An antenna array in which the received signal is continually monitored in respect of interference (usually adjacent or co-channel). Its directional characteristics are then automatically adjusted to null out the interference. Such a concept often employs computer control of a planar type antenna.

Adaptive Channel Allocation

A method of multiplexing wherein the information-handling capacities of channels are not predetermined but are assigned on demand.

Adaptive Communication

Any communication system, or portion thereof, that automatically uses feedback information obtained from the system itself or from the signals carried by the system to modify dynamically one or more of the system operational parameters to improve system performance or to resist degradation.

Adaptive Compression

Data compression software that continuously analyzes and compensates its algorithm (technique), depending on the type and content of the data and the storage medium.

Adaptive Differential Pulse Code Modulation


Adaptive Equalization

An electronic technique that allows a modem to continuously analyze and compensate for variations in the quality of a telephone line.

Adaptive Interframe Transform Coding

A class of compression algorithms commonly used in video codecs to reduce the data transmission rate.

Adaptive Multi-Rate Speech Codec

AMR. Technology deployed into GSM networks to increase voice capacity by up to 4 times. GSM equipment vendors are deploying EDGE and AMR into GSM/GPRS networks simultaneously.

Adaptive Predictive Coding

APC. Narrowband analog-to-digital conversion that uses a one-level or multilevel sampling system in which the value of the signal at each sampling instant is predicted according to a linear function of the past values of the quantized signals. APC is related to linear predictive coding (LPC) in that both use adaptive predictors. However, APC uses fewer prediction coefficients, thus requiring a higher sampling rate than LPC.

Adaptive Pulse Code Modulation

A way of encoding analog voice signals into digital signals by adaptively predicting future encodings by looking at the immediate past. The adaptive part reduces the number of bits per second that another rival and more common method called PCM (Pulse Code Modulation) requires to encode voice. Adaptive PCM is not common because, even though it reduces the number of bits required to encode voice, the electronics to do it are expensive. See Pulse Code Modulation.

Adaptive Radio

A radio that monitors its own performance, monitors the path quality through sounding or polling, varies operating characteristics, such as frequency, power, or data rate, and uses closed-loop action to optimize its performance by automatically selecting frequencies or channels.

Adaptive Retransmission Algorithms

Used by self-adjusting timers to determine and dynamically set timers to effectively adjust data traffic in the event the link is slower than usual due to congestion or their network conditions.

Adaptive Routing

A method of routing packets of data or data messages in which the system's intelligence selects the best path. This path might change with altered traffic patterns or link failures.

Adaptive Speed Leveling

A modem technology that allows a modem to respond to changing line conditions by changing its data rate. If the line quality improves , the modem attempts to increase the data rate. If the line quality declines, the modem compensates by lowering the data rate. This is also known as adaptive equalization.

Adaptive Switching

The adaptive switch is an intelligent node that sits in the network and evaluates the packets that are coming through the network. The switching will make the decision around what it wants to do with those packets. This platform sits on the edge of the network in the Gateway GPRS Support Node (GGSN) or acts as a replacement to the GGSN. It can only force QoS on a network-wide basis.


Automated Directory Assistance Service. A service from Northern Telecom which automates the greeting and inquiry portion of the directory assistance call. With ADAS, directory assistance callers are greeted by the automated system and asked to state the name of the city and the listing they are seeking. They are then connected with an operator. The ADAS service knocks a few seconds off each directory assistance call.


Apple Desktop Bus. A low-speed serial bus used on Apple Macintosh computers to connect input devices to the Macintosh CPU (central processing unit). Normally the ADP connects via an 8-pin round or DIN connector.


  1. Analog-to-Digital Converter or Analog to Digital Conversion. A method of sampling and encoding analog signal to create a digital signal. The process is accomplished by a coded, also known as a DSP (Digital Signal Processor). See also Codec and DSP.

  2. Automated Data Collection. A variety of technologies that provide for automation of the function of data collection. Examples include bar code readers, OCR (Optical Character Recognition), OMR (Optical Mark Recognition), voice recognition, and smart cards.


Advanced Data Communications Control Procedures, A bit-oriented ANSI-standard communications protocol. It is a link-layer protocol. ADCCP is ANSI's version of SDLC/HDLC.


Association of Data Communications Users.

Add Path request

A request made by the network to add a path using the Add Path packet, which establishes a multi-hop path between two network nodes. Although the two nodes are usually the source and destination nodes of a Virtual Wavelength Path, there are cases in which other nodes might want to establish a path between them. Unlike the Restore Path request, the Add Path request is never flooded; it is instead forwarded using information carried in the path itself (source routing). See VWP.


The process wherein a part of the information carried in a transmission system is demultiplexed (dropped) at an intermediate point and different information is multiplexed (added) for subsequent transmission. The remaining traffic passes straight through the multiplexer without additional processing.

Add/Drop multiplexer

See ADM.

Add-in Card

An expansion board that fits into the computer's slots and is used to expand the system's memory or extend the operation of another device.


  1. A telephone system feature which allows connecting a third telephone to an existing conversation. This "add-on" feature is initiated by the originator of the call. The feature is also known as "Three-Way Calling."

  2. Hardware, often referred to as peripheral equipment, that is added to a system to improve its performance, add memory or increase its capabilities. Voice mail, Automated Attendant and Call Detail Recording Equipment are examples of PBX add-on devices. Lucent, Nortel and some other manufacturers call them applications processors.

  3. A call center/marketing term. A technique to increase the revenue of an order, for example, two dozen instead of one dozen or, two green shirts bought and sold with matching green tie.

Add-on Conference

A PBX feature. Almost always used in conjunction with another feature called consultation hold, this feature allows an extension user to add a third person to an existing two-person conversation. The user places an existing central office call or internal call on Hold, and obtains system dial tone. The user can then call another internal extension or an outside party. After speaking with the "consulted" party, the originating phone reactivates the initiating command (typically a button push) and creates a three- party conference with the call previously placed on Hold.

Add-on Conference ” Intercom Only

Allows a telephone user to add someone else to an existing intercom (within-the-same office) conversation.

Add-on Data Module

Plug-in circuit cards which allow a PBX to send and receive analog (voice) and digital (data) signals.

Added Bit

A bit delivered to the intended destination user, to the intended user information bits and the delivered overhead bits. An added bit might be used to round out the number of bits to some error checking scheme, for example.

Added Block

Any block, or other delimited bit group, delivered to the intended destination user in addition to intended user information bits and delivered overhead bits. See also Extra Block.

Additional Call Offering

See ACO.

Additional Cooperative Acceptance Testing


Additional Period

Billing periods charged after initial, first or minimum period on a call. Usually, long distance toll/DDD has a one-minute initial period at premium rate; subsequent "additional" minutes (period) are billed at a lower rate. Additional period billing increments vary by long distance company.

Additive Primaries

By definition, three primary colors result when light is viewed directly as opposed to being reflected: red, green and blue (RGB). According to the tri-stimulus theory of color perception, all other colors can be adequately approximated by blending some mixture of these three lights together. This theory is harnessed in color television and video communications. It doesn't work so well in color printing where special colors are often printed separately.

Additive White Gaussian Noise

AWGN. See White Noise.


Administrative Directory Management Domain. A X.500 directory management domain run by a PTT (Posts, Telegraph, and Telephone administration) or other public network provider.


An address comprises the characters identifying the recipient or originator of transmitted data. An address is the destination of a message sent through a communications system. A street address (i.e. 123 Elm Street, Normal, OK) is your physical address. A telephone number is considered the address of the called person. In computer terms, an address is a set of numbers that uniquely identifies the physical or logical location of something ” a workstation on a LAN, a location in computer memory, a packet of data traveling through a network. On the Internet, addresses are based on the IP protocol, which uses a 32-bit code in the IP header to identify host addresses. Web URLs and e-mail addresses are arbitrary text addresses that correlate to IP addresses. They are maintained in directory service databases. For a longer explanation, see Internet Address.

Address Complete Message

ACM. A CCS/SS7 signaling message that contains call-status information. This message is sent prior to the called customer going off- hook.

Address Field

In data transmission, the sequence of bits immediately following the opening flag of a frame identifying the secondary station sending, or designated to receive, the frame.

Address Field Extension

EA. A Frame Relay term defining a 2-bit field in the Address Field, identifying the fact that the address structure is extended beyond the 2-octet default. Frame Relay standards provide for extension of the address field up to 60 bits, which extension will be implemented as the popularity of Frame Relay grows, placing pressure on the standard addressing convention.

Address Filtering

A way of deciding which data packets are allowed through a device. The decision is based on the source and destination MAC (Media Access Control, the lower part of ISO layer two) addresses of the data packet.

Address Harvester

The programs that search Web pages and/or filter newsgroup traffic looking for email addresses to unload unsolicited advertising (or worse ).

Address Mapping

Technique that allows different protocols to interoperate by translating addresses from one format to another. For example, when routing IP over X.25, the IP addresses must be mapped to the X.25 addresses so that the IP packets can be transmitted by the X.25 network. See also address resolution.

Address Mask

An electronic messaging term. A bit mask used to select bits from a network address (e.g. Internet) for sub-net addressing. The mask is 32 bits long and selects the network portion of the address and one or more bits of the local portion. Sometimes called sub-net mask.

Address Message

A message sent in the forward direction that contains address information, the signaling information required to route and connect a call to the called line, service-class information, information relating to user and network facilities and call-originator identity or call-receiver identity.

Address Message Sequencing

In common-channel signaling, address message sequencing is a procedure for ensuring that address messages are processed in the correct order when the order in which they are received is incorrect.

Address Munging

Modifying one's e-mail address in such a way that computers can't read it but humans can.

Address Prefix

An ATM term. A string of 0 or more bits up to a maximum of 152 bits that is the lead portion of one or more ATM addresses.

Address Records

See A Records.

Address Resolution

  1. The process of discovering a device's address. An internetworking term. A discovery process used when, as in LAN protocols such as TCP/IP and IBM NetBIOS, only the Network Layer address is known and the MAC address is needed to enable delivery to the correct device. The originating end station sends broadcast packets with the device's NLA to all nodes on the LAN; the end station with the specified NLA address responds with a unicast packet, addressed to the originating end station, and containing the MAC address. See Address Resolution Protocol.

  2. An ATM term. Address Resolution is the procedure by which a client associates a LAN destination with the ATM address of another client or the bus.

Address Resolution Protocol

ARP. The Internet protocol used to map dynamic Internet addresses to physical (hardware) addresses on local area networks. Limited to networks that support hardware broadcasts.

Address Screening

A service provided by Switched Multi-megabit Data Service (SMDS). Address Screening allows the network to compare the Source Address of the transmitting party to a list of addresses for including (or excluding) end-points into (or out of) a virtual network.

Address Separator

A character that separates the different addresses in a selection signal.

Address Signaling

Signals either the end user's telephone or the central office switching equipment that a call is coming in.

Address Signals

Address signals provide information concerning the desired destination of the call. This is usually the dialed digits of the called telephone number or access codes. Typical types of address signals are DP (Dial Pulse), DTMF, and MF.

Address Space

The amount of memory a PC can use directly is called its address space. MS-DOS can directly access 1024K of memory (one megabyte). A protected mode control program like Microsoft Windows 3.x or OS/2 can directly address up to 16 megabytes of memory. Here is a definition of address space, as supplied by the Personal Computer Memory Card International Association (PCMCIA) as address space applies to PCMCIA cards: "An address space is a collection of registers and storage locations contained on a PC Card which are distinguished from each other by the value of the Address Lines applied to the Card. There are three, separate, address spaces possible for a card. These are the Common Memory space, the Attribute Memory space and the I/O space."

Address Table

A table stored in routers, bridges and switches that enables these devices to know where on the network to forward information.


The characteristic of a network device enabling it to send and receive messages independently due to its unique identification code.

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