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Glossary of broadband terminology: A

A-side unbundling: Apparently it's happening in Australia. I assume it the same as "local loop"
Access Line: The physical telecommunications circuit connecting an end user location with the serving central office in a local network environment. Also called the local loop or "last mile." See also Local Loop.
Access Network: That portion of a public-switched network that connects access nodes to individual subscribers. The access network today is predominantly passive twisted pair copper wiring.
Access Nodes: Points on the edge of the access network that concentrate individual access lines into a smaller number of feeder lines. Access nodes may also perform various forms of protocol conversion. Typical access nodes are DLC systems concentrating individual voice lines to T-1lines, cellular antenna sites, PBXs, and ONUs.
Access Rate: The transmission speed of the physical access circuit between the end user location and the local network. This is generally measured in bits per second; also called Access Speed.
Adapter: See Adapter Card.
Adapter Card: Circuit board or other hardware that provides the physical interface to a communications network; an electronics board installed in a computer which provides network communication capabilities to and from that computer; a card that connects the DTE to the network. Also called a Network Interface Card. See also Data Termination Equipment and Network Interface Card.
ADSL: Asymmetric Digital Subscriber Line - also known by G.413 DMT. Like ISDN, ADSL uses standard phone lines to deliver high-speed data communications. But while ISDN's transmission speed is limited to 64 kbps per channel, ADSL technology can deliver upstream (from the user) speeds of 640 kbps and downstream (to the user) speeds of more than 6 mbps. Theoretically 100mbs is achievable, but a realistic maximum is 50-65mbs. ADSL uses the portion of a phone line's bandwidth not utilized by voice, allowing for simultaneous voice and data transmission. Until late 1996, ADSL was still in development, it only really began to be commercially available around January '98. The roll out is continuing apace, Stateside at least.
ADSL Forum: The organization developing and defining xDSL standards, including those affecting ADSL, SDSL, HDSL, and VDSL. Members participate in committees to vote on ADSL specifications; auditing members receive marketing and technical documentation.
ADSL Transmission Unit - Central Office: The ADSL modem or line card that physically terminates an ADSL connection at the telephone service provider's serving central office.
ADSL Transmission Unit - Remote: The ADSL modem or PC card that physically terminates an ADSL connection at the end user's location.
Always On: Current dial-up services require the user to "make a call" to the ISP. The connection is only active during the duration of the call. Most xDSL implementations (including ADSL, UADSL, and SDSL) enable the connection to be always on in a fashion similar to a LAN.
American Wire Gauge: A measure of the thickness of copper, aluminum, and other wiring in the US and elsewhere. Copper cabling typically varies from 18 to 26 AWG, the higher the number, the thinner the wire. The thicker the wire, the less susceptible it is to interference. In general, thin wire cannot carry the same amount of electrical current the same distance that thicker wire can.
Analog: An electrical signal or wave form in which the amplitude and/or frequency vary continuously.
Analog Front End: The analog front ends are responsible for converting the digital signal to analog and force the signal onto the twisted pair line.
Application Specific Integrated Circuit: A chip designed for a specific application. Examples of an ASIC application can be SDSL or other broadband solutions.
Asymmetrical Digital Subscriber Line: BellCore term for delivery of digital information over ordinary copper phone lines. ADSL uses a system of frequency division whereby lower frequency POTS signals are delivered to the home unaltered while digital signals traverse the phone line at higher frequencies for delivery to end stations such as a video CODEC or PC. Asymmetric refers to the fact that the downstream (to the user) channels can outweigh the upstream (to the network) channels by a ratio as high as 20:1. This asymmetry is a good fit for video on demand and Internet access applications where the paradigm is a small request up to the network and a large delivery to the user.
Asynchronous Transfer Mode: See ATM below
Asynchronous Transmission: Data transmission one character at a time to the receiving device, with intervals of varying lengths between transmittals and with start bits at the beginning and stop bits at the end of each character, to control the transmission. In xDSL and in most dial-up modem communications, asynchronous communications are often found in Internet access and remote office applications. See Synchronous Transmission.
ATM - Asynchronous Transfer Mode: A protocol that packs digital information into 53-byte cells (5-byte header and 48 bytes of payload) that are switched throughout a network over virtual circuits (standardized by the ITUT in 1988 to create a BISDN). Its ability to accommodate multiple types of media (voice, video, and data) makes it a likely player for full service networks based on ADSL and VDSL.

A connection-oriented, packet-like switching technology that utilizes virtual channels instead of dedicated circuits to carry data in fixed-length (1 cell = 53 bytes) over a broadband network.
ATM25: A high speed, cell based, direct connection to a network where an ATM25 network interface card (NIC) is installed so that the user can access any host connected to the network.
ATM Adaption Layer 5: A standard adopted by the ATM Forum for a class of service called High Speed Data Transfer.
ATM Cell: An ATM cell is 53 bytes long containing a 5-byte header and a 48-byte payload. The header of an ATM cell contains all necessary information for data to reach the appropriate endpoint. The payload portion of an ATM cell can contain any type of information, be it voice, video, or data.
ATM Connection: An ATM connection is actually one physical connection between two endpoints, that contains multiple VCs. Furthermore, multiple VCs can be grouped to traverse a VP. See also Permanent Virtual Circuit, Switched Virtual Circuit, Virtual Channel Identifier, and Virtual Path Identifier.
ATM Forum: The organization tasked with developing and defining ATM standards.
ATM Passive Optical Network: A passive optical network running ATM.
ATM25: ATM Forum-defined 25.6 Mbps cell-based user interface based on IBM token ring network.
Attenuation: The dissipation of the power of a transmitted signal as it travels over the copper wire line.
ATU-R's: .
Available Bit Rate: Provides a guaranteed minimum capacity but allows data to be bursted at higher capacities when the network is free.