AAL (ATM Adaptation Layer) - the AAL divides the user information into segments suitable for packaging into a series of ATM cells. AAL1 is typically used for CBR traffic such as voice and real time video, while AAL5 is typically used for VBR and VBR traffic such as bursty LAN data.

AAL Connection - an association established by the AAL between two or more next higher layer entities.

AAL-1 (ATM Adaptation Layer Type 1) - AAL functions in support of constant bit rate, time-dependent traffic such as voice and video.

AAL-2 (ATM Adaptation Layer Type 2) - This AAL is still undefined by the International Standards bodies. It is a placeholder for variable bit rate video transmission.

AAL-3/4 (ATM Adaptation Layer Type ¾) - AAL functions in support of variable bit rate, delay-tolerant data traffic requiring some sequencing and/or error detection support. Originally two AAL types, i.e. connection-oriented and connectionless, which have been combined.

AAL-5 (ATM Adaptation Layer Type 5) - AAL functions in support of variable bit rate, delay-tolerant connection-oriented data traffic requiring minimal sequencing or error detection support.

ABR (Available Bit Rate) - a type of traffic for which the ATM network attempts to meet that traffic's bandwidth requirements. It does not guarantee a specific amount of bandwidth and the end station must retransmit any information that did not reach the far end.

A/B Switch - A feature found on all new cellular telephones permitting the user to select either the “A” (non-wireline) carrier or the “B” (wireline) carrier when roaming away from home.

AC (Alternating current) - Typically refers to the 120 volt electricity delivered by your local power utility to the outlet in your wall. The current alternates between plus and minus, 60 times a second.

“A” Carrier - See Non-Wireline Cellular Company.

Acceptance Test - The final test of a new telephone system.

Acceptance Trials - Trials carried out to determine if the specified performance and haracteristics have been met.

Access Fee - A special fee that local telephone companies are allowed to charge all telephone customers for the right to connect with the local phone network. The fee is paid by cellular subscribers, as is a federal 3% telephone excise tax.

Access Level - The level of programs and data to which a given terminal and/or operator are granted access.

ACD (Automatic Call Distribution/Distributor - A specialized phone system for handling many incoming calls. Typically used by airlines, rent-a-car companies, hotels, etc., an ACD has four functions. First, it will recognize and answer an incoming call. Second, it will look in its database for instructions on what to do with that call. Third, based on that database’s instructions, it will send the call to a recording that “somebody will be with you soon, please don’t hang up.” Fourth, it will send the call to one operator of a group of operators as soon as that operator has completed their previous call and/or the caller has heard the canned message.

AC/DC Ringing - A common way of signaling a telephone. An alternating current (AC) rings the phone bell and a direct current (DC) is used to work a relay to shut the ringing off when the called person answers.

AC Distribution Cabinet - A cabinet housing fuses and/or circuit breakers that distribute commercial or reserve AC power to equipment in a telephone building. May be floor or wall mounted.

ACM (Address Complete Message) - A BISUP call control message from the receiving exchange to sending exchange indicating the completion of address information.

ACO (Alarm Cut-Off) - A switch used to silence an audible alarm while maintaining the visual signal.

ACR (Allowable Cell Rate) - 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.

AC Standby Power (Reserve Power) - Power delivered by an engine alternator set (generator) or UPS during interruption of commercial power.

Active Communication Satellite - A satellite with a self-contained energy source, designed to transmit radio communication signals back to earth.

Adapter - A fitting that supplies a passage between two sets of equipment when they cannot be directly interconnected.

Adapter Card - Physical interface card that supports a particular device and its use of a particular technology. For example, an ATM network adapter enables a computer to connect to an ATM network.

Adaptive Differential Pulse Code Modulation (ADPCM) - A technique that allows analog voice signals to be carried on a 32K bps digital channel. Sampling is done at 8Hz with 4 bits used to describe the difference between adjacent samples.

Adaptive Pulse Code Modulation - A technique that effectively reduces occupied bandwidth per active speaker by reducing sampling rates during periods of overflow peak traffic.

Address - A unique identity of each network station on a LAN or WAN.

Address Mask - a bit mask used to identify which bits in an address (usually an IP address) are network significant, subnet significant, and host significant portions of the complete address. This mask is also known as the subnet mask because the subnetwork portion of the address can be determined by comparing the binary version of the mask to an IP address in that subnet. The mask holds the same number of bits as the protocol address it references.

Address Prefix - 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 Resolution - The procedure by which a client associates a LAN destination with the ATM address of another client or the BUS.

Adjacency - The relationship between two communicating neighboring peer nodes.

ADTF (ACR Decrease Time Factor) - For ABR, the time permitted between sending RM-cells before the rate is decreased to the ICR (Initial Cell Rate of .01 to 10.23 seconds with .5 as the default).

AFI (Authority and Format Identifier) - Identifies the format and type of address in use.

Agent (SNMP) - a component of network- and desktop-management software, such as SNMP, that gathers information from MIBs.

AHFG (ATM-attached Host Functional Group) -The group of functions performed by an ATM-attached host that is participating in the MPOA service.

AIM (ATM Inverse Multiplexer) - A term discontinued because of conflict with an established product. Refer to AIMUX.

AIMUX (ATM Inverse Multiplexing) - A device that allows multiple T1 or E1 communications facilities to be combined into a single broadband facility for the transmission of ATM cells.

Airtime - Actual time spent talking on the cellular telephone.

AIS (Alarm Indication Signal) - In T1, an all ones condition used to alert a receiver that its incoming signal (or frame) has been lost. The loss of signal or frame is detected at the receiving end, and the failed signal is replaced by all the ones condition which the receiver interprets as an AIS. The normal response to this is AIS is for the receiving end to generate a yellow alarm signal as part of its transmission towards the faulty end. (The AIS itself is sometimes called a Blue Signal).

alarm - an unsolicited message from a device, typically indicating a problem with the system that requires attention.

Alarm or Indicator Fuse - Type of fuse used on distribution and equipment frames used in parallel with larger load fuses to indicate the operation of the load fuse.

Alarm Center - A location generally within a technical control facility that receives local and remote alarms.

Alarm Condition - Term used to describe equipment in a failed state.

Alarm Display - Attendant console indicators show the status of the telephone system. There are usually two types of displays, minor and major. Minor displays are not usually service affecting, while a major is, and requires immediate attention.

Alarm Pair - A cable pair used to carry alarm circuits. For example, circuits from remote pressure contactors to centrally located alarm equipment in a cable pressurization system.

Alarm Relay - Relay which operates a circuit signaling an alarm.

A-Law - The PCM coding and companding standard used in Europe.

Algorithm - A prescribed finite set of well defined rules or processes for the solution of a problem in a finite number of steps. In normal English, it is the mathematical formula for an operation, such as computing the check digits on packets of data that travel via packet switched networks. In T-1, an “algorithm” is a “recipe” for making a computer do something. A sequence of steps followed by a computer to accomplish a task.

Alphanumeric - A message or other type of readout containing both letters (“alphas”) and numbers (“numerics”). In cellular, “alphanumeric memory dial” is a special type of dial-from-memory option that displays both the name of the individual and that individual’s phone number on the cellular phone handset. The name also can be recalled by using the letters on the phone keypad. By contrast, standard memory dial recalls numbers from number-only locations.

Alternate Routing - A mechanism that supports the use of a new path after an attempt to set up a connection along a previously selected path fails.

Alternating Current Generator - An alternator; a rotating machine which produces an alternating current output.

Alternator - A generator that produces electric power in the form of alternating current and voltage.

Ambient - Surrounding; often used as shorthand for surrounding air.

Ambient Noise Level - The level of acoustic noise existing in a room or other location, as measured with a sound level meter. It is usually measured in decibels above a reference level of 0.00002 newton per square meter in SI units, or 0.0002 dyne per square centimeter in cgs units.

Ambient Temperature - Temperature of surrounding fluid, air, or gas.

AMI (Alternate Mark Inversion) - A line coding format used on T1 facilities that transmits ones by alternate positive and negative pulses.

AMI (ATM Management Interface) - the user interface to Marconi ForeThought switch control software (SCS). AMI lets users monitor and change various operating configurations of Marconi switches and network module hardware and software, IP connectivity, and SNMP network management.

Ammeter - Instrument which measures the amount of current in amperes flowing in a circuit.

Amp - Abbreviated form of ampere.

Ampacity - Current carrying capacity, expressed in amperes, of a wire or cable under stated thermal conditions.

Amperage - The strength of an electric current in amperes.

Amperage Rating - The amperage which may be safely applied to a circuit, service or equipment.

Ampere - A measure of electrical current intensity.

Ampere-Hour - When the current is one ampere, the quantity of electricity that flows in one hour. Multiplying current in amperes by time of flow in hours equals ampere hours. In this case, batteries are often rated over an eight-hour period.

Analog - The traditional method of modulating radio signals so that they can carry information. AM (amplitude modulation) and FM (frequency modulation) are the two most common methods of analog modulation.

Analog Channel - A channel which transmits in analog waveforms.

Analog Device - A simple computer-type device able to operate on analog inputs and produce analog outputs.

Analog/Digital Converter - A device which converts an Analog signal to a digital signal.

Analog Signal - An electrical signal that varies continuously over an infinite range of voltage or current values, as opposed to a digital signal, which varies discretely be-tween two values, usually one and zero. It is easiest to think of analog signals as sine waves of various sizes.

Analog Value - A continuously variable parameter.

Ancestor Node - A logical group node that has a direct parent relationship to a given node (i.e., it is the parent of that node, or the parent's parent.)

Annunciator Panel - Name given to the visual and audible portion of the alarm interface/isolation facility which utilizes visual/audible panels throughout the telephone office.

ANSI (American National Standards Institute) - a private organization that coordinates the setting and approval of some U.S. standards. It also represents the United States to the International Standards Organization.

Antenna - A device for transmitting or receiving, or transmitting and receiving signals. An antenna’s shape and size depends on what frequency and the strength of the signal it is receiving.

Antenna Tower - A self-supporting steel structure able to carry VHF or microwave antennae at different heights above ground.

Antimony Battery - Storage cell which utilizes lead-antimony alloy plates.

API (Application Program Interface) - a language format that defines how a program can be made to interact with another program, service, or other software; it allows users to develop custom interfaces with Marconi products.

APP (application program) - a complete, self-contained program that performs a specific function directly for the user.

Apparatus Blank - A blank panel used to cover open equipment space in a rack or shelf.

Applet - A program designed to be executed from within another application. Unlike an application, applets cannot be executed directly from the operating system. Web browsers, which are often equipped with Java virtual machines, can interpret applets from Web servers. Because applets are small in files size, cross-platform compatible, and highly secure (can't be used to access users' hard drives), they are ideal for small Internet applications accessible from a browser.

AppleTalk - a networking protocol developed by Apple Computer for communication between Apple's products and other computers. Independent of the network layer, AppleTalk runs on LocalTalk, EtherTalk and TokenTalk.

Application Layer - Layer seven of the ISO reference model; provides the actual end-user interface.

APS (Automatic Protection Switching) - Equipment installed in communications systems to detect circuit failures and automatically switch to redundant, standby equipment.

Arcing - Sustained luminous passage of current between contacts or electrodes.

ARP (Address Resolution Protocol) - a method used to resolve higher level protocol addressing (such as IP) into the appropriate header data required for ATM; i.e., port, VPI, and VCI; also defines the AAL type to be used.

Arrestor - A device used to protect equipment from lightning, electrical storms, etc.

ASCII (American Standard Code for Information Interchange) - a standard character set that (typically) assigns a 7-bit sequence to each letter, number, and selected control characters.

Assigned Cell - a cell that provides a service to an upper layer entity or ATM Layer Management entity (ATMM-entity).

asxmon - a Marconi program that repeatedly displays the state of the switch and of all its active ports.

ATC (ATM Transfer Capability) - Octet 5A in the BBC IE. The ATC is used to identify a sub category of ATM service category. For example, ATC 5 represents a CBR Service Category with a BCOB of X and requiring end-to-end timing.

ATDM (Asynchronous Time Division Multiplexing) - a multiplexing technique in which a transmission capability is organized into a priori, unassigned time slots. The time slots are assigned to cells upon request of each application's instantaneous real need.

ATM (Asynchronous Transfer Mode) - a transfer mode in which the information is organized into cells. It is asynchronous in the sense that the recurrence of cells containing information from an individual user is not necessarily periodic.

ATM Address - Defined in the UNI Specification as 3 formats, each having 20 bytes in length.

ATM Anycast Capability - The ability to allow an application to request a point-to-point connection to a single ATM end system that is part of an ATM group.

ATM Forum - an international non-profit organization formed with the objective of accelerating the use of ATM products and services through a rapid convergence of interoperability specifications. In addition, the Forum promotes industry cooperation and awareness.

ATMF-PNNI - Refers to a PNNI (Private Network Node Interface or Private Network-to-Network Interface) which has been standardized by the ATM Forum.

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

ATM Link - a virtual path link (VPL) or a virtual channel link (VCL).

ATM Peer-to-Peer Connection - a virtual channel connection (VCC) or a virtual path connection (VPC) directly established, such as workstation-to-workstation. This setup is not commonly used in networks.

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

ATM User-to-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 layer entities or between two or more ATM entities). The communication over an ATM Layer connection may be either bi-directional or unidirectional. The same Virtual Channel Identifier (VCI) is used for both directions of a connection at an interface.

atmarp - a Marconi program that shows and manipulates ATM ARP entries maintained by the given device driver. This is also used to establish PVC connections.

atmconfig - a Marconi program used to enable or disable SPANS signaling.

atmstat - a Marconi program that shows statistics gathered about a given adapter card by the device driver. These statistics include ATM layer and ATM adaptation layer cell and error counts. This can also be used to query other hosts via SNMP.

Audible Ring - The signal which rings the telephone set.

Audible/Visual Panel - An alarm panel usually equipped with audible, visual and alarm cut-off features.

AUI (Attachment User Interface) - IEEE 802.3 interface between a media attachment unit (MAU) and a network interface card (NIC). The term AUI can also refer to the rear panel port to which an AUI cable might attach.

Auto-logout - a feature that automatically logs out a user if there has been no user interface activity for a specified length of time.

Automatic Equalization - The process of compensating for distortion of data communications signals over an analog circuit. With regard to battery systems, an automatic means to raise the battery voltage slightly to equalize the voltage on all of the battery cells.

Automatic Power Transfer - Automatic transfer of a load from one power source to another, or to a standby source.

Autotransformer - Transformer in which both the primary and secondary currents flow through one common part of the coil.

Auxiliary Power - An alternate source of electric power, serving as back-up for the primary power at the station main bus or prescribed sub-bus.

AvCR (Available Cell Rate) - Measure of effective available bandwidth. Available Cell Rate applies to all service categories except UBR.

AW (Administrative Weight) - The link or nodal-state parameter set by an administrator to indicate preference.

AWG (American Wire Gauge) - Measurement scale for non-ferrous (copper, bronze, etc.) wire.