Access Network: The so called last mile that connects individual subscribers to access nodes and is typically copper twisted pair wiring.

Access Nodes: Points in the access network that concentrate the individual access lines into feeder lines such as T1 lines, cellular antenna sites, PBXs and optical Network Units (ONUs).

ADSL (Asymmetric Digital Subscriber Line): A twisted pair copper line that carries data at a rate from 1.5 Mbps to 9 Mbps downstream to the subscriber and from 16 Kbps to 754 Kbps upstream, depending on equipment used and line distance.

ATM (Asynchronous Transfer Mode): A data protocol based on high speed cell transmission which may be run over ADSL. Because of its short packet structure it is good for real time voice and video.

ATU-C (ADSL Transmission Unit - Central Office): The device at the end of an ADSL line that stands between the line and the first item of equipment in the subscriber premise. It may be integrated within an access node.

ATU-R (ADSL Transmission Unit - Remote): The device at the end of an ADSL line that stands between the line and the first item of equipment in the subscriber premise. It may be integrated within an access node.

AWG (American Wire Gauge): A Measure used to denote the thickness of wire. The higher the number, the thinner the wire is.

bps (Bits per Second): A measurement of transmission speed.

BERT (Bit Error Rate Test): A test that shows how many received bits are in error in relationship to the number of bits transmitted.

BRI (Basic Rate Interface): A basic rate ISDN interface consisting of one 16 Kbps D (Data) channel and two 64 Kbps B (Bearer) channels for voice and/or data.

Bridge Tap: Copper wire taps on the local loop that, while not causing problems in the voice band, tend to have adverse affects at high frequencies.

CAP (Carrierless Amplitude): A version of QAM which modulates data onto the transmission line utilizing a technique which cancels out the carrier frequency which is then recreated on the far end.

CLEC (Competitive Local Exchange Carrier): A telecommunications service provider which has no local access of its own by rents from the local exchange.

CO (Central Office): A switching center that connects local copper loops to the core network in a given geographical area.

CODEC (Coder DEcoder): Converts analog voice signals into U-law or A-law encoded samples.

CPE (Customer Premises Equipment): Any network equipment found in the customers premises.

Core Network: Combination of switching offices and transmission media which create the core fabric of Inter-exchange of National Exchange networks.

CSA (Carrier Serving Area): A defined area served by a LEC, RBOC or telco, often using Digital Loop Carrier (DLC) technology.

CSU/DSU (Channel Service Unit/Data Service Unit): Data communications equipment used to connect to digital access lines in framing segments of 64 Kbps.

DCE (Data Communications Equipment): A communications device, such as a modem, that connects a DTE to the network.

DMT (Discrete Multi Tone): A signaling technique which divides the frequency band into smaller discrete bands which can then be partially or completely repressed if interference is encountered in the discrete band.

DSL (Digital Subscriber Line): Basic Rate ISDN service provided on a single twisted copper pair. Modems on either end of a single twisted pair wire that delivers ISDN Basic Rate Access.

DSLAM (Digital Subscriber Line Access Multiplexer): A device which concentrates ADSL subscriber lines onto a single ATM line.

DS0 (Digital Signal 0): 64 Kbps digital data signal often used to carry voice.

DS1 (Digital Signal 1): 1.544 Mbps digital data signal able to carry twenty four voice channels, also known as T1.

DS2 (Digital Signal 2): Four T1 frames transmitted at a data rate of 6.312 Mbps.

DTE (Data Terminiation Equipment): The computer or terminal that acts as a data source or destination connects to the network via a DCE.

E1: The European equivalent to T1 which transmits data at a rate of 2.048 Mbps and can carry up to 30 voice channels.

Echo Cancellation: A technique used to cancel the unwanted feedback of the phone network by subtracting the echo based on testing of the line on initial creation of the connection.

Feeder Network: That part of the switched network which connects access nodes to the core network.

FEXT (Far End CrossTalk): Interference between two signals at the end of the lines remote from the telephone switch.

FTTCab (Fiber to the Cabinet): Network architecture where the telephone switch connets to a cabinet via fiber optics which then converted to copper to feed the subscriber.

FTTH (Fiber to the Home): Network architecture where an optical fiber runs from a telephone swtich to the subscriber's premises or home.

FTTK or FTTC (Fiber to the Kerb): A network architecture using fiber runs from telephone switch to a kerbside distribution point close to the subscriber where it is converted to a copper pair.

HFC (Hybrid Fiber Coax): A network architecture using fiber to a distribution point which converts the signal to coax.

HDSL (High data rate Digital Subscribe Line): A technology used to provide T1 with two copper pairs or E1 with three copper pairs which reduces and often eliminates the need for repeaters on the line.

ISDL: A technology similar to HDSL used to deliver data at ISDN speeds of 128 Kbps.

IXC (Inter-exchange Carrier): A long distance phone company.

LEC (Local Exchange Carrier): A telephone service provider which has access to the local loop.

Local Loop: The twisted pair of copper wires and the associated terminating equipment that connects to the central office.

Loop Qualification: Qualification of twisted copper pair for data services.

Modulation: The method of encoding signals onto a different waveform usually for the purposes of transmission.

NEXT (Near End CrossTalk): Signal interference between pairs of lines at the telephone switch end.

N-ISDN (Narrowband ISDN): Same as ISDN.

NTE (Network Terminiation Equipment): The communication equipment at the end of a communications line.

POTS (Plain Old Telephone Service): Basic analog telephone service which utilizes the bandwidth from DC up to 4 KHz.

POTS Splitter: A filter used to separate digital ADSL signals from POTS signals so that they do not interfere with one another.

PRI (Primary Rate Interface): An ISDN interface consisting of one 64 kbps D (Data) channel and 23 or 30 B(Bearer) channels for voice and data.

PSTN (Public Switched Telephone Network): A public telephone network.

PTT (Postal, Telegraph and Telephone): The standard term for state owned telephone companies in Europe.

RADSL (Rate Adaptive ADSL): A version of ADSL adapts itself to the line so that it can transmit at the fastest speed the line can handle.

RBOC (Regional Bell Operating Company): One of the seven US telephone companies that resulted from the break up of AT&T

SDSL (Symmetric Digital Subscriber Line): A technology similar to HDSL only it utilizes only a single telephone line and carries POTS as well.

SNR (Signal to Noise Ratio): A measure of the amount of noise on the transmission medium in relationship to the amount of signal.

T1: Same as DS1.

Telco: The generic term used for telephone companies throughout the world which encompasses RBOCs, LECs and PTTs.

UTP (Unsheilded Twisted Pair): A cable containing one or more twisted pair in a plastic sheath.

VDSL (Very high data rate Digital Subscriber Line): A technology utilizing the existing copper and operating at data rates from 12.9 to 52.8 Mbps with corresponding maximum reach ranging from 4500 feet to 1000 feet of 24 gauge twisted pair.

WAN (Wide Area Network): A service offered by telcos to extend local area networks beyond the limit of buildings and campuses to facilitate communications between remote facilities.