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 Digital Loop Carrier systems concentrating individual voice lines to T1 lines, cellular antenna sites, PBXs, and Optical Network Units (ONUs).

ADSL Asymmetric Digital Subscriber Line: Modems attached to twisted pair copper wiring that transmit from 1.5 Mbps to 9 Mbps downstream (to the subscriber) and from 16 kbps to 800 kbps upstream, depending on line distance.

APON ATM Passive Optical Network: a passive optical network running ATM.

ATM Asynchronous Transfer Mode: an ultra high speed cell based data transmission protocol which may be run over ADSL.

ATM25 ATM Forum defined 25.6Mbit/s cell based user interface based on IBM token ring network.

ATU-C and ATU-R ADSL Transmission Unit, Central or Remote: the device at the end of an ADSL line that stands between the line and the first item of equipment in the subscriber premises or telephone switch. It may be integrated within an access node.

BDSL Same as VDSL.

B-ISDN Broadband Integrated Digital Network: A digital network with ATM switching operating at data rates in excess of 1.544 or 2.048 Mbps. ATM enables transport and switching of voice, data, image, and video over the same infrastructure.

CATV Community Access Television: also known as Cable TV.CPE Customer Premises Equipment: that portion of the ADSL system residing within the customer's premises.

Core Network Combination of switching offices and transmission plant connecting switching offices together. In the U.S. local exchange Core Networks are linked by several competing Interexchange networks; in the rest of the world (now) the Core Network extends to national boundaries.

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

DSLAM Digital Subscriber Line Access Multiplexer: specifically, a device which takes a number of ADSL subscriber lines and concentrates these to a single ATM line

DS0 Digital Signal 0: 64 kbps digital representation of voice.

DS1 Digital Signal 1: Twenty four voice channels packed into a 193 bit frame and transmitted at 1.544 Mbps. The unframed version, or payload, is 192 bits at a rate of 1.536 Mbps.

DS2 Digital Signal 2: Four T1 frames packed into a higher level frame transmitted at 6.312 Mbps.

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

E1 European basic multiplex rate which packs thirty voice channels into a 256 bit frame and transmitted at 2.048 Mbps.

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

FEXT Far End CrossTalk: the interference occurring between two signals at the end of the lines remote from the telphone switch.

FTTCab Fibre To The Cabinet: network architecture where an optical fiber connects the telephone switch to a street-side cabinet where the signal is converted to feed the subscriber over a twisted copper pair.

FTTH Fibre To The Home: network where an optical fibre runs from telephone switch to the subscriber's premises or home.

FTTK or FTTC Fiber To the Kerb: a network where an optical fiber runs from telephone switch to a kerbside distribution point close to the subscriber where it is converted to a copper pair.

HFC Hybrid Fibre Coax: a system (usually CATV) where fibre is run to a distribution point close to the subscriber and then the signal is converted to run to the subscriber's premises over coaxial cable.

HDSL High data rate Digital Subscribe Line: Modems on either end of one or more twisted pair wires that deliver T1 or E1 speeds. At present T1 requires two lines and E1 requires three. See SDSL for one line HDSL.

ISDL Uses ISDN transmission technology to deliver data at 128kbps into an IDSL "modem bank" connected to a router.

ISP Internet Service Provider: an organization offering and providing Internet services to the public and having its own computer servers to provide the services offered.

LAN Local Area Network.

LEC Local Exchange Carrier: one of the new U.S. telephone access and service providers that have grown up with the recent U.S. deregulation of telecommunications.

MPEG Motion Picture Experts Group: the group that has defined the standards for compressed video transmission.

NAP Network Access Provider: another name for the provider of networked telephone and associated services, usually in the U.S.

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

N-ISDN Narrowband ISDN: same as ISDN

NSP Network Service Provider: the term for an organization offering and providing value added network services on a telecommunications network.

NTE Network Termination Equipment: the equipment at the ends of the line.

OC3 Optical Carrier 3: an optical fibre line carrying 155mbps; a U.S. designation generally recognized throughout the telecommunications community worldwide.

ONU Optical Network Unit: A form of Access Node that converts optical signals transmitted via fiber to electrical signals that can be transmitted via coaxial cable or twisted pair copper wiring to individual subscribers.

PON Passive Optical Network: the usual acronym for a fibre based transmission network containing no active electronics.

POTS Plain Old Telephone Service: the only name recognized around the world for basic analog telephone service. POTS takes the lowest 4kHz of bandwidth on twisted pair wiring. Any service sharing a line with POTS must either use frequencies a bove POTS or convert POTS to digital and interleave with other data signals.

PTT The generic European name usually used to refer to state owned telephone companies.

RADSL Rate Adaptive ADSL: a version of ADSL where the modems test the line at start up and adapt their operating speed to the fastest the line can handle.

RBOC Regional Bell Operating Company: one of the seven U.S. Telephone companies that resulted from the break up of AT&T.

SDSL Symmetric Digital Subscriber Line: HDSL plus POTS over a single telephone line. This name has not been adopted by a standards group, but is being discussed by ETSI. It is important to distinguish, however, as SDSL operates over POTS and would be suitable for symmetric services to premises of individual customers.

STS-1 SONET basic transmission rate of 51.84 Mbps.

T1 Same as DS1.

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

TPON Telephony over Passive Optical Network: telephony using a PON as all or part of the transmission system between telephone switch and subscriber.

UDSL Unidirectional HDSL as proposed by one company in Europe without much sign of interest from anyone else.

VADSL Very high speed ADSL: same as VDSL (or a subset of VDSL, if VDSL includes symmetric mode transmission)

VDSL Very high data rate Digital Subscriber Line: Modem for twisted-pair access 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: Private network facilities, usually offered by public telephone companies but increasingly available from alternative access providers (sometimes called Competitive Access Providers, or CAPs), that link business network nodes.