A A and B signaling Procedure most often used in T1 transmission facilities operated by U.S. telephone companies, in which one bit, robbed from each of the 24 subchannels in every sixth frame, is used for carrying dial and control information. A-Bus Internal microprocessor bus (various manufacturers). A/B Roll A video editing technique where the scene or sound on two different reels are played (rolled) together simultaneously to perform a transition or special effect. A/D Analog to digital. A/D Converter Analog to Digital converter. Generic term for any device that changes continuous wave (analog) activity to binary (digital) code, or vice versa. Modems and codecs are A/D converters. A/N Alphanumeric. AAV See alternative access vendor. abandoned call Disconnection by the calling party before the called party answers. ABATS Automated bit access test system. abbreviated and delayed ringing After two rings, a call is automatically transferred to another station. abbreviated dialing The dialing of a special 2- or 3-digit code instead of a standard telephone number to reach a specific subscriber. ABEND Abnormal end of task. ABI Application Binary Interface. ablate To remove. Used in reference to the formation of laser-read-able "pits" in the recording layer of optical discs. AC-DC ringing Telephone ringing that uses alternating current to operate a ringer and direct current to stop the ringing when the called party answers. ACA See automatic circuit assurance. ACC Asynchronous Communications Controller. ACCAP Autocoder-to-COBOL Conversion Aid Program (IBM). accept rate The percentage of characters an OCR recognizes (correctly or incorrectly) from the total number of characters in the document. access arm The device in a disk or disc drive that holds the read/write heads and moves them into position. access charge A fee paid for the use of a local line. access code A digit or series of digits necessary to be connected to a private line for dial access. access control The process of restricting access to a workstation or network. access delay Measure of delay between the time a data packet arrives at a station to the time the packet begins transmission. access line A telephone circuit that connects a customer location to a network switching center. access method (1) Techniques and rules for moving data between main storage and input/output devices. (2) A means of granting network utilization rights to one or more PC users (e.g., via token-passing or CSMA/CD). access network Local portion of WAN that connects customer equipment to the interexchange servicing office. access time 1. The time interval between the instant at which an instruction control unit starts a call for data and the instant at which delivery of data is completed. 2. Time interval between the instant data is requested to be stored and the instant storage is begun. account code A feature that allows a station user to enter a cost accounting or client billing code into a PBX system before initiating a long-distance call. See also forced account code. accounting rate Cost per traffic unit used to establish international telecommunications accounts and tariffs. accuracy A means of juudging OCR. The extent to which a document is recognized with no errors as measured as a percentage. ACD See automatic call distributor. ACE Advanced Computing Environment. acetate-base film A film substrate used in microform production. Considered a safety film (i.e. meets ANSI safety standards.) ACF Advanced Communications Function. ACF/NCP Advanced Communication Function for the Network Control Program. An IBM term. ACF/VTAM Advanced Communication Function/Virtual Telecommunications Access Method. An IBM term. achromatic Having no color. ACK See acknowledgment code. ACK/NAK/END Acknowledged/not acknowledged/inquiry. acknowledgment (ACK) code A method in which one or more characters are generated at a receiving device to indicate to the sending device that information has been received correctly. ACMS Application Control and Management System (Digital Equipment). acoustic coupler A device that converts electrical signals into audio signals, enabling data transmission over the public telephone network through a conventional handset. ACS Advanced Communications Service. ACSE Association Control Service Elements, defined in ISO 8649 and ISO 8650. actinic The chemical change violet or ultraviolet light produces in certain photosensitive film. active branching device A device that converts an optical input into two or more optical outputs with gain or regeneration. active display area The part of an image that falls inside the borders of the display screen. active matrix LCD LCD display technique that uses a transistor for each monochrome or each red, green, and blue dot. It provides sharp contrast, speeds screen refresh and eliminates loss of cursor (submarining) on standard LCD screens. active video The portion of the video signal that holds the picture. active video area The area of a TV monitor, excluding the border, where clips, special effects and edited video can be viewed. actuator Mechanism that moves an object. ACU See automatic calling unit. Ada High-level programming language (developed for the US Department of Defense, named after Ada Augusta Lovelace). ADAPSO Association of Data Processing Service Organizations, formed to serve the common interests of over 750 corporate members by providing an extensive collection of computer-related products and services. adapter A fitting that supplies a passage between two sets of equipment that cannot be directly interconnected. 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 (ADPCM A technique that allows analog voice signals to be carried on a 32K-bps digital channel. Sampling is performed at 8Hz with 3 or 4 bits used to describe the difference between adjacent samples. Adaptive Differential Pulse Code Modulation (ADPCM) A digitizing standard that allows a voice conversation to be carried within a 32Kbps digital channel. adaptive equalization An electronic technique that allows a modem to continuously analyze and compensate for variations in the quality of a telephone line. adaptive pulse code modulation A technique that effectively reduces occupied bandwidth per active speaker by reducing sampling rates during periods of overflow peak traffic. adaptive routing A means of selecting the optimum path for message transfer or packet routing. adaptive transform coding (ATC) A voice coding technique used between 9.6K bps and 32K bps. ADC See analog-to-digital conversion. ADCC Asynchronous Data Communications Channel. ADCCP See advanced data communications control procedure. add-on conference Permits a telephone user to add someone else onto an existing conversation. add-on data modules Plug-in circuit boards that allow a PBX to receive and transmit both digital (data) and analog (voice) signals. address A coded means of designating the originating and receiving terminal for data transmission purposes. Multiple terminals on one communications line, for example, must have unique addresses. A message reaching a switching center carries an address before its text to indicate its destination. Address Resolution Protocol (ARP) The protocol within TCP/IP that determines whether a data packet's source and destination are in Data-Link Control (DLC) or Internet Protocol (IP) format. ARP is necessary for proper routing of data packets. address, group A method of simultaneously transmitting data to specific groups of stations. address, international telephone A code of 12 digits or less that specifies a unique address for any telephone in the world (i.e., a country or regional identity code of 1, 2, or 3 digits; a 3-digit numbering plan area code; a 2- or 3-digit central office code; plus a 4-digit station number). address, telephone A 10-digit number that specifies the location of a particular telephone and consists of a 3-digit area code, 3-digit central office code, and 4-digit station number. addressability The ability to place information at a certain chosen area in an image. Also, the number of dots per inch that a printer can place on the page. addressable capacity The number of locations on an image that are addressable. ADPCM See adaptive differential pulse code modulation. ADR Automatic Dialog Replacement. In video editing, the process of replacing the dialog recorded on-location with dialog recorded in the studio. Also called looping. ADSI See analog display services interface. ADSL See asymmetrical digital subscriber line. ADSTAR Automated Document Storage And Retrieval. Generic term for systems that identify, select, and display images that have been previously electronically stored. ADU Automatic dialing unit. Advanced Communication Function (ACF) IBM software products that incorporate IBM's SNA and administer intercommunication between computers. Advanced Data Communications Control Procedure (ADCCP) A bit- oriented data link protocol endorsed by the American National Standards Institute (ANSI). ADCCP is identical to HDLC and a superset of SDLC. advanced mobile phone service (AMPS) AT&T's version of cellular radio for mobile telephones. advanced private line termination (APLT) AT&T term referring to a PBX user's ability to access all the services of an Enhanced Private Switched Communications Services (EPCS) network. advanced program-to-program communications (APPC) IBM's protocol for communication between PCs in a mainframe-based network. APPC ensures that programs have access to network resources when needed and that network resources are not corrupted. Advanced Research Projects Agency (ARPA) U.S. Department of Defense agency that supports the ARPAnet resource-sharing computer network. AFIPS See American Federation of Information Processing Societies. AFNOR French standards organization. aggressive recognition An OCR that uses rules and parameters that increase the chance of a mistake. AI Artificial Intelligence. AIIM Association for Information and Image Management. AIM Associated Index Method. AIOD See automatic identification of outward dialing. AIW APPN Implementer's Workshop. AIX Advanced Interactive eXecutive; a UNIX operating environment variant developed by Interactive Systems for the IBM PC/RT, PS/2, and System/370 lines of computers. AJAD Tools and techniques used to automate Joint Application Development (JAD) tasks for defining new computer systems. alarm call An operator or automatic device calls a given telephone number at a time specified in advance by the subscriber, and makes an appropriate announcement. alarm code A feature allowing the attendant or extension user to program a call to ring the extension at a prearranged time. alarm display An LED or LCD readout on the attendant console that alerts the operator to a problem. alarm lamps Small lights on the attendant console that indicate problem conditions (i.e., a minor alarm for a malfunction that is not serious; a major alarm if the system is not functioning; a console alarm for a problem related to the console; and a battery alarm to indicate the system is operating on battery power). ALBO (automatic line buildout) Eases DSU/CSU installation by enabling DSU/CSU to adjust signal output automtically according to line distance. algorithm A set of instructions or mathematical formulas used to solve a given communications problem. all number calling (ANC) Telephone calling numbers containing all numerical digits instead of a combination of two letters and five numbers. all point addressability The ability in a layout program to place text or graphics anywhere on the page. Some programs are restricted to row/column restrictions. all trunks busy (ATB) A single tone that is interrupted at 60 ipm rate to indicate a condition when all trunks in a particular group are engaged. ALOHA A University of Hawaii research system designed to control contention in packet transmission networks. alphanumeric A set of characters containing letters, numbers, and other symbols such as punctuation marks. Altair Motorola's wireless LAN product. Altair offers compatibility with Novell NetWare and utilizes low-power microwave transfer. alternate mark inversion A signal carrying binary digits in which successivemarks are normally positive or negative but equal in amplitude, and in which space (no value) is of zero amplitude. Also called bipolar. alternate routing A standby communications path used when a primary data transmission path is unavailable. alternate voice/data (AVD) Method of providing voice-grade service on a data circuit. alternative access vendor (AAV) A company that provides its customers with an alternative to the local telephone company for local transport of private line and special access telecommunications services. Alternative access vendors are also called competitive access providers (CAPs). ALU See arithmetic logic unit. AM See amplitude modulation. ambient noise The noise level that is present all the time. ambiguity resolution The process in OCR that uses multiple information sources to make the best choice for a character or word from several alternatives. American Federation of Information Processing Soci Organization of computer-related societies. Members include the Association for Computer Machinery, the Institute of Electrical and Electronic Engineers Computer Group, Simulation Councils, Inc., and American Society for Information Science. American National Standards Institute (ANSI) An organization that develops American industry standards. American Standard Code for Information Interchange A 7-bit plus parity-bit code advocated by the American Standards Association. ASCII is designed to establish a uniform means of transferring information between data processing systems, communications systems, and terminal equipment. American wire gauge The American standard that specifies the wire size. AMI Alternate mark inversion. AMIS See audio messaging interchange specification. amplifier An electrical device that strengthens the signal in an analog transmission. amplitude The distance between high or low points of a signal or waveform. The peak value of a varying quantity. amplitude modulation (AM) The technique of varying the amplitude or wavelength of a carrier wave in direct proportion to the strength of the input signal while maintaining a constant frequency and phase. AMPS See advanced mobile phone service. AMR Automatic Message Routing. AMS Asymmetric Multiprocessing System (IBM). analog An electrical signal that varies in amplitude or frequency depending on changes in sound, light, heat, etc. analog cellular The standard for equipment used for cellular telephone transmissions, using radio wavelengths and frequencies to transmit phone calls. analog channel A channel that imposes no specified limits on transmitted data (i.e., there are no discrete packages or pulses of information). analog display services interface (ADSI) A telecommunications standard, developed by Bellcore, for communicating with telephones supporting a display screen analog loopback Method of testing modems by disconnecting the telephone line and looping back the transmitted line signal into the local receiver. analog signal An electrical signal that varies in amplitude or frequency depending on various changes such as sound, light, heat, etc. analog transmission A signaling technology in which sound waves or other information are converted into electrical impulses of varying strengths. See also digital signal. analog-to-digital conversion A method by which analog signals are converted to digital signals. analog/digital converter A device that converts an analog transmission signal into digital format. ANC See all-number calling. ancillary equipment Synonymous with auxiliary equipment; equipment not directly controlled by the processing unit. ANDF Architecture Neutral Distribution Format; a foundation on which completely portable applications can be built. (Open Software Foundation) OSI, TCP/IP, and DECnet Phase IV. (Digital Equipment) angstrom (A) A measure of optical wavelength = 10 meters: extensively replaced by nanometers (10 meters). ANI See automatic number identification. annotation The ability to attach notes to graphics or images by typing them in, using a light pen or digitizing tablet. Useful for clarifying documents or editing images. announcement service A station user hears a prearranged announcement upon dialing a predetermined access code. ANS American National Standards. ANSA Advanced Network System Architecture. ANSI See American National Standards Institute. ANSI T1X9.4 American National Standards Institute's Sonet standard. answer signal Signal sent in a backward direction (e.g., from the called subscriber to the central office), which indicates that the called line has answered. answer supervision An off-hook signal transmitted toward the calling end of a switched connection when the called party answers. answer, universal night A PBX feature that permits any station to answer an incoming trunk call when no attendant is present by dialing a single digit (usually after working hours). answerback A signal or sequence of signals from a receiving device indicating that it is ready to accept or acknowledge receipt of data. The signal can be received audibly (through a loudspeaker) at the transmitting end for manual operation or electronically for automatic operation. antenna Device used for transmitting or receiving electromagnetic radiation at radio frequencies. AOL America OnLine. AOS Advanced Operating System (Data General). AOS/VS Advanced Operating System/Virtual Storage (Data General). AP 1. Array Processor. 2. Attached Processor. aperture fluorescent lighting A scanner design that uses a fluorescent light source with a narrow unfrosted strip that lets brighter light pass through with each scan, boosting the accuracy of the captured data. API Application program interface. A set of approved software calls and routines that can be referenced by an application program to access underlying network services. APIA Application Program Interface Association; a group of computer and communication product vendors, formed in 1988 to develop a standard program interface specification for interoperability between different implementations of electronic mail (E-mail) systems on both large and small computers. APL A problem-solving computer programming language developed for mathematical and economic use. APLT See advanced private line termination. APP Application Portability Profile; a guideline for government agencies trying to achieve application portability, interoperability, and scalability. APPC Advanced peer-to-peer communications. See peer communications and Advanced Program-to-Program Communications. APPI Advanced peer-to-peer internetworking. AppleShare Apple Computer's commercial implementation of its AppleTalk protocols. AppleTalk Apple Computer's local area network. Apple Macintosh computers and LaserWriter laser printers are compatible with AppleTalk. AppleTalk Filing Protocol (AFP) Set of Apple Computer services that handle remote file access across a LAN. AFP is a presentation- layer service within the OSI model. AppleTalk Link Access Protocol (ALAP) Set of Apple Computer services that govern packet transmission across an AppleTalk network. ALAP operates at the OSI data-link layer. application layer Top level of ISO's seven layer reference mode of communications protocols, it interfaces between end users and the presentation layer. application program The primary data processing program within a system. Application programs normally contain no input/output coding except in the form of macro instructions that transfer control to supervisory programs. APPN Advanced Peer-to-Peer Networking (IBM); communications capabilities available within IBM's SNA that offer intermediate noderouting, dynamic network services, and improved administration. APPNTAM APPN Topology and Accounting Management. ARC 1. Advanced RISC Computing. 2. Attached resource computer. Archie A search tool for files stored on FTP servers. architecture The structure of a computer system and the details for how it functions and how its components interact. archival quality The extent to which a reproduced image will last. Though not a precise standard, archival quality media should hold data safely for 50 years. archive To copy data, often compressed, and save it on tape or a different disk for either historical purposes or as a backup. ARCnet Attached Resource Computer Network. Datapoint Corporation's 2.5 Mbps baseband, token passing, media-access protocol. ARCnetPlus Attached Resource Computer Network. Datapoint Corporation's 20 Mbps baseband, token passing, media-access protocol. area code A 3-digit code that precedes the central office code in a complete 10-digit telephone number; used when the called party is in a numbering plan area other than that of the calling party. area code restriction The ability of a switching system to identify specific 3-digit area codes and allow or deny calls to those codes. area, numbering plan (NPA) A geographic subdivision of the territory covered by a national or integrated numbering plan. An NPA is identified by a distinctive area code (NPA code). arithmetic logic unit (ALU) Unit within a microprocessor that computes logical and arithmetical operations. ARO 1. Automatic Recovery Option (NCR). 2. After receipt of order. AROM Alterable Read-Only Memory. ARP See Address Resolution Protocol. ARPA See Advanced Research Projects Agency. ARPANET Advanced Research Projects Agency Network; packet-switching communications network of ARPA (US Department of Defense, Advanced Research Project Agency) ARQ See automatic repeat request. Arrhenius Lifetime Plot A graphical means of estimating the life of any material, by charting the end of the material's life at super-high temperatures, and interpolating how lone it would last at a more normal temperature. ARS See automatic route selection. artificial intelligence (AI) A device's capacity to perform human intelligence functions, such as reasoning and learning. ARU Audio response unit. ASAP Automatic Self-Allocating Processor. ASCII See American Standard Code for Information Interchange. ASI Adapter support interface is an IBM protocol stack supporting token-ring NICs. ASIS American Society for Information Science. ASMP Asymmetrical multiprocessing. ASN.1 Abstract Syntax Notation One, defined in ISO 8824 and ISO8825. ASP Auxiliary Storage Pool. aspect ratio The relationship of width to height. ASPI Advanced SCSI Programming Interface. ASR See automatic send/receive. assembler A software application that translates assembly language (assembler source code) into a computer's machine language. assembly language Assembler source code. assigned night answer (ANA) See night service. asymmetrical compression 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. asymmetrical digital subscriber line Permits the transmission of video signals into offices or homes over existing telephone networks thorough the addition of special equipment to each end of a line. It is a one way video transmission technology with control signals returning from the office or home at 16 kilobits per second. asymmetrical modulation A technique in which a high-speed modem simulates near full-duplex transmission by using the majority of the bandwidth on a dial-up call for transmission in one direction, while using a smaller portion for information flowing in the opposite direction. asynchronous A variable or random time interval between successive characters, operations, or events. Asynchronous data transmission provides for variable intercharacter time, but for fixed interbit time within characters. See also start-stop transmission, synchronous. asynchronous communications software A software package, which, when used together with a modem allows a PC user to access various communications information systems via a telephone line. asynchronous computer A computer in which the initiation of a new event or operation is dependent upon a signal generated by the completion of the previous event or operation. asynchronous data switching A PBX system that supports asynchronous (a sequence wherein operations occur in a sporadic time frame) data. asynchronous digital subscriber loop (ADSL) A compression technology that allows the delivery of video through copper wire. asynchronous transfer mode (ATM) High-speed packet switching technique used for broadband ISDN which packages data in 32 byte pieces. asynchronous transmission Data transmission in which alphanumeric characters are sent at irregular intervals, each having a start and stop bit preceding and immediately following each character. Asynchronous communications software used in conjunction with a modem allows a PC user to access various communications information systems via a dial-up or leased-line modem connection. AT command set The de facto standard command set used by most modems. The AT command set includes a specific set of ASCII characters which, when sent to a modem, initiate various functions, such as go off-hook, dial, echo characters, and hang up. ATB See all trunks busy. ATM See asynchronous transfer mode. attendant Refers to a local console operator, for example, on a PBX. See also operator. attendant busy override See executive override. attendant call forwarding setup and cancel This feature permits the system attendant to establish and cancel automatic forwarding of calls for any extension. Individual stations need not have any call forwarding features. See also call forwarding -- all calls, call forwarding -- busy, and call forwarding -- do not answer. attendant camp-on A facility that enables the attendant to connect calls to busy extensions or trunks for automatic completion when the party is free. See also camp-on and call park. attendant CO trunk to CO trunk connection A feature that allows the attendant to connect a central office (CO) trunk call to another CO trunk and then release the call from the console. attendant console A centralized cordless operator position for controlling calls and connecting functions. attendant control of trunk group access The attendant controls and restricts access from stations to various trunk groups. Restricted calls are usually routed to the attendant. attendant direct station selection with busy lamp The ability to place or complete calls to stations within the PBX through the attendant console by using a nonblocking push button associated with the desired station; a light indicates whether the station is busy or idle. attendant DISA code setup enable A feature that permits the attendant to change the direct-in system access (DISA) security code that callers must dial to access the system. attendant forced release Feature that permits the attendant to automatically disconnect all parties on a given circuit when the attendant employs the feature and enters the circuit. attendant incoming call control Feature that automatically diverts incoming calls to a specified station after a certain number of rings. attendant locked loop operation Permits the console attendant to recall or supervise any call that was processed. attendant lockout Feature that disallows the attendant from re-entering a call unless recalled by the PBX extension.Also called Attendant restriction. attendant loop release An attendant console loop becomes available for subsequent calls once the previous call is directed to the appropriate station. attendant loop transfer Permits the attendant to transfer calls to other attendants. attendant override A warning tone initiated from an attendant console that enables the attendant to join an ongoing conversation in a busy trunk. attendant position Telephone switchboard operator's position. It provides either automatic (cordless) or manual (plug and jack) operator controls for incoming and/or outgoing telephone calls. attendant recall Forwarded calls, calls on hold, or calls on camp-on status are returned to the console if not answered within a preset period. attendant repertory dialing Feature that allows an attendant to program certain buttons on the console for frequently dialed numbers.Also called automatic dialing. attendant restriction See attendant lockout. attendant serial call See serial call. attendant station busy-out The attendant can busy-out an extension to prevent that station from originating or receiving calls; the attendant can also remove the busy-out condition. attendant timed recall The attendant is automatically alerted when a call extended through the console (or held at the console) has not been answered within a prescribed time. attendant transfer An inside party alerts the attendant to transfer a call by flashing the switchhook or dialing a preselected code and then dialing another extension to complete the transfer without assistance. attendant-controlled conference A feature that allows the attendant to set up conference calls with a specified number of parties plus the attendant. attended operation An environment in which two workstations are required to establish a connection, transfer information, and convert it from voice to data mode. See also unattended operation. attenuation A technique that decreases the magnitude of current, voltage, or power of a transmitted signal. ATTIS AT&T Information Systems. attribute Properties describing a file that take on a defined set of values. audible ringing tone Signal heard by the calling party during the ringing interval. audible signal control A feature that allows attendants or users to set the volume of telephone set signals, such as tones and bells. audio frequencies Frequencies that can be heard by the human ear (usually 30 to 20,000 cycles per second). audio messaging interchange specification (AMIS) A standard for networking voice-mail systems. Audio Response Unit A device that provides synthesized voice responses to dual-tone multi-frequency signaling input. These devices process calls based on the caller's input, information received from a host data base, and information carried with the incoming call. audiotex Interactive voice response equipment and services. Permits a computer to interpret spoken commands and, if appropriate, deliver the requested data. audit trail A record of transactions in an information system that provides a means of identifying and verifying the accurate transmission of network data. authentication The verification process used in the Motorola Integrated Radio System (MIRS) system which automatically checks subscriber identification to provide additional security to end- users. authoring Software that helps multimedia developers create interactive presentations without much programming overhead. authorization code An identification number that the caller enters for billing purposes when placing a call. auto selection The ability of photo manipulation/imaging editing software to select entire areas of the image within a specified range of color values. auto-baud (ABR) An asynchronous communications technique in which a called modem or computer analyzes transmitted data and determines such characteristics as transmission rate, parity, and the number of stop bits contained in the data. AUTODIN The automatic digital network serving the U.S. Department of Defense providing both message- and circuit-switching capability. The circuit-switching portion provides point-to-point service between like circuit terminals; the message-switching element provides service to large-volume terminals and unlike terminals. automated attendant A device connected to a PBX that performs most of the functions of an attendant, such as answering and transferring calls. To access the system, users usually press buttons on their dialpad in response to options presented, and depending on the information required. automatic answer A machine answers a call to an unattended telephone line. automatic blue frame In painting, animation, and imaging editing programs, the ability to display a faint blue copy of the previous version or cel while editing the current image to match positions precisely or create an accurate trace. automatic call distributor (ACD) A device that attaches to a telephone system to connect incoming calls to a given extension or any free extension without operator intervention. automatic callback A feature that allows the station user, when encountering an internal station busy signal, to dial a 1-or 2-digit code and hang up. When both parties (calling and called) are free, the system automatically rings and connects the parties. While activated, this feature does not prevent the calling station from either initiating or receiving calls. automatic calling unit (ACU) Also called automatic dialing unit. A dialing device supplied by the communications common carrier. This device allows a business machine to dial calls automatically over a communications network. automatic camp-on A station user can automatically camp on a busy station by remaining off hook; when the called party extension becomes idle, the call rings through. See also camp-on. automatic circuit assurance (ACA) A PBX feature that facilitates the identification of malfunctioning trunk lines. automatic dialer Device that automatically generates a pre-programmed telephone number, and is accessible through the telephone keypad. Also called repertory dialer, autodialer, and automatic dialing unit. automatic dialing Feature accessed by pressing a button on the telephone, which then automatically dials a pre-programmed number. Also called reparatory dialing. automatic equalization Equalization of a transmission channel that is adjusted while sending special signals. automatic error detection/correction A feature that automatically detects and corrects errors in a data transmission signal. automatic exclusion First station to gain entry to a line prevents other stations from accessing the same line. automatic hold This feature enables a caller to press a button to place an existing call on hold to answer a second call. automatic identification of outward dialing (AIOD) A hardware system or PBX feature that automatically obtains the identity of a calling station over a separate data link for automatic message accounting. automatic message-switching center According to its destination, this is the location through which messages are automatically routed. automatic number identification (ANI) Feature that automatically identifies the calling station's extension number, or outside party's telephone number. automatic preselection See line preference. automatic recall See attendant recall. automatic recovery Permits restart of the switched message flow after a fatal system failure. The recovery process is started by an operator response when the system is reloaded, and works from special records saved in the communications data bank. automatic redial A technique that allows a primary network workstation to continually redial a secondary station until a successful connection is established. automatic repeat request (ARQ) A feature that automatically initiates a request for retransmission when a data transmission error is detected during communication. automatic route selection (ARS) Computerized or mechanically-controlled selection and routing of outgoing calls over the least-cost route for the type of call initiated. automatic send/receive (ASR) A teleprinter unit with keyboard, page printer, paper tape reader, and paper tape punch that allows users to prepare messages and edit them off-line on paper tape for automatic transmission. automatic station release A PBX system feature that automatically releases and locks out an extension when a digit is not dialed within the dial-timeout period, exceeds the interdigit timeout period, or is not disconnected after a call is completed. The PBX can be programmed to activate an alarm at the console when a lockout condition exists. automatic station restriction Prevents unauthorized (and unaccountable) phone calls from vacant hotel rooms by automatically restricting outbound calls when a guest is checked out from the room and cancelling the restriction when a guest checks in. automatic time-out If a station stays off-hook without dialing or is busy for a long time, switching equipment automatically connects the station to an intercept position. automatic vehicle location A wireless service that allows a central dispatcher to track the exact longitude and latitude of a moving or stationary vehicle. automatic wake-up See alarm call. Autoreversing/Autopositive Types of COM film which yield a negative image (white characters on black background.) Negative images are easier to see in a microfiche reader. autostitch The ability of a hand-scanner's software to combine several passes over a document into a single image. AUTOVON Automatic voice network (U.S. Military) auxiliary equipment access The ability of a system to interface with such auxiliary equipment as dial dictation and paging systems. AVD See alternate voice/data. AVDcircuits Alternate voice/data circuits that are able to manage both voice and data traffic. AWG see American wire gauge.