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Alternating Current. An electrical power transmission system in which the direction of current flow alternates on a periodic basis.

AC Alternating Current (AC):
Current in which the charge-flow periodically reverses.

AC Resistance:
The total resistance offered by a device in an alternating current circuit due to inductive and capacitive effects, as well as the direct current resistance .

Active Hub:
Multiported device that amplifies LAN transmission signals.

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 management tasks such as ensuring that tokens are not lost or that frames do not circulate indefinitely.

A device that enables any or all of the following a) different sizes or types of plugs to mate with one another or to fit into a telecommunications outlet/connector; b) the rearrangement of leads; c) large cables with numerous wires to fan out into smalle

A mechanical media termination device designed to align and join fiber optic connectors. Often referred to as a coupling, bulkhead, or interconnect sleeve.

Adaptive Routing:
See dynamic routing.

Advanced Data Communications Control Protocol.

Aerial Cable:
A cable suspended in the air on poles or other overhead structure

Aluminum Interlocked Armor.

Air Core:
A telephone outside plant cable construction for aerial and duct installation in which the insulated conductors in the cable core are surrounded by air.

Air Spaced Coaxial Cable:
One in which air is essentially the dielectric material. A spirally wound synthetic filament, beads, or braided filaments may be used to center the conductor.

Air-Handling Plenum:
A designated area, closed or open, used for environmental air.

Alarm indication signal. In a T1 transmission, an all-ones signal transmitted in lieu of the normal signal to maintain transmission continuity and to indicate to the receiving terminal that there is a transmission fault that is located either at, or upstream from, the transmitting terminal.

Telephone cable sheath employing a corrugated aluminum shield and an outer polyethylene jacket.

A type of cable consisting of insulated conductors enclosed in a continuous, closely fitting aluminum tube.

Alternating Current (AC):
Electric current that continually reverses its direction. It is expressed in cycles per second (hertz or Hz).

Alternating Voltage:
The voltage developed a cross a resistance or impedance through which alternating current is flowing.

Aluminum Conductor:
An aluminum wire or group of wires not suitably insulated to carry electrical current.

Aluminum-Steel Conductor:
A composite conductor made up of a combination of aluminum and steel wires.

Amplitude Modulation. Modulation technique whereby information is conveyed through the amplitude of the carrier signal. Compare with FM and PAM. See also modulation.

Referring to a set of conditions that exist independently of the system of interest.

Ambient Temperature:
The temperature of the medium surrounding an object. Generally a lower temperature than the temperature at which the cable is operating.

American Wire Gauge (AWG):
The standard system used for designating wire diameter. The lower the AWG number, the larger the diameter. Also called the Brown and Sharpe (B&S) wire gauges.

Ampere. A standard unit of measurement for electrical current flow.

Ampere (AMP):
The unit of cur rent. One ampere is the current flowing through one ohm of resistance at one volt potential.

In the terminology of wave motion, the height of the wave. Amplitude is usually measured from a reference point of 0. In electrical waves, amplitude is typically expressed in volts.

A signaling format that uses continuous physical variables such as voltage amplitude or frequency variations to transmit information.

Analog Signal:
A signal in which the intelligence is represented by continuously varying quantities.

Analog Transmission:
Signal transmission over wires or through the air in which information is conveyed through variation of some combination of signal amplitude, frequency, and phase.

American National Standards Institute. The principle group in the US. for defining standards.

Application Programming Interface. A set of tools and procedures provided by the programmer of an application so that other programmers can control, exchange data with, or extend the functionality of an application.

Appliance Wire and Cable:
Appliance wiring material is a classification of Underwriters' Laboratories, Inc., covering insulated wire and cable intended for internal wiring of appliances and equipment. Each construction satisfies the requirements for use in particular applications.

Application Layer:
Layer 7 of the OSI reference model. This layer provides services to application processes (such as electronic mail, file transfer, and terminal emulation) that are outside of the OSI model. The application layer identifies and establishes the availability of intended communication partners (and the resources required to connect with them), synchronizes cooperating applications, and agreement on procedures for error recovery and control of data integrity. Corresponds roughly with the transaction services layer in the SNA model. See also data link layer, network layer, physical layer, presentation layer, session layer, and transport layer.

Advanced Peer-to-Peer Networking. Enhancement to the original IBM SNA architecture. APPN handles session establishment between peer nodes, dynamic transparent route calculation, and traffic prioritization for APPC traffic. Compare with APPN+. See also APPC.

Next-generation APPN that replaces the label-swapping routing algorithm with source routing. Also called high-performance routing. See also APPN.

Aramid Yarn:
Strength elements that provide tensile strength, support, and additional protection of fiber bundles. It is commonly referred to as Kevlar (a DuPont trademark).

Arc Resistance:
The time required for an arc to establish a conductive path in a material.

Attached Resource Computer Network. A 2.5-Mbps token-bus LAN developed in the late 1970s and early 1980s by Datapoint Corporation.

A braid or wrapping of metal, usually steel or aluminum, used for additional mechanical protection in harsh environments.

The American Standards Association, former name of ANSI.

Autonomous system boundary router. ABR located between an OSPF autonomous system and a non-OSPF network. ASBRs run both OSPF and another routing protocol, such as RIP, ASBRs must reside on a nonstub OSPF area.

Referring to a standard 7-bit character system that includes the alphanumeric characters and printer control codes.

Application-Specific Integrated Circuit. A custom chip for a specific application.

A cable sheath consisting of a corrugated aluminum (A) shield, corrugated steel (S) shield, flooding compound and an outer polyethylene (P) jacket.

Automatic spanning tree. Function that supports the automatic resolution of spanning trees in SRB networks, providing a single path for spanning explorer frames to traverse from a given node in the network to another. AST is based on the IEEE 802.1 standard.

Asynchronous time-division multiplexing. Method of sending information that resembles normal TDM, except that time slots are allocated as needed rather than preassigned to specific transmitters. Compare with FDM, Statistical multiplexing, and TDM.

Asynchronous Transfer Mode. A broadband transmission system using 53-octet packets over a cell-switched network at speeds up to 2.2 GBPS.

A loss in the amplitude or strength of a signal due to an interaction with the signal's media. Generally expressed in decibels.

Attenuation to Crosstalk Ratio (ACR):
The difference between attenuation and crosstalk, measured in dB, at a given frequency. Important characteristic in networking transmission to assure that signal sent down a twisted pair is stronger at the receiving end, after being attenuated, than are a

Attachment unit interface. IEEE 802.3 interface between an MAU and a NIC (network interface card). Also called transceiver cable.

Average Rate:
The average rate, in kilobits per second (kbps), at which a given virtual circuit will transmit.

Abbreviation for American Wire Gauge.