ADSL (Asymetrical Digital Subscriber Line): A method of transmitting data over a standard pair of copper wires that can reach speeds of 8Mbps.

B channel: An ISDN data channel.

Bonding: An old method of combining one or more B channels on an ISDN device to provide greater than 64K conductivity. This is generally used for video conferencing.

BRI (Basic Rate Interface): The method a telco uses to deliver the ISDN line for single-line use. It generally consists of two 64K B channels and one 16K D channel.

Call Teardown: Telco term for hanging up or disconnecting from the switch.

Class C: Third class in the older naming scheme for network numbers. It is a block of 256 IP numbers. Example, is the author's class C.

CO or Central Office: The location on the phone company network where the phone company switches are located and your phone line terminates.

D channel: An ISDN signaling channel used to set up, teardown and do in-call signaling.

In-Band Signaling: A method of signaling where the signalling information is transmitted on the same channel as the data. For example, your analog modem uses tones or pulses to dial the phone number and signal the switch to hang up.

ISDN: Integrated Services Digital Network.

ISP: Internet Service Provider.

MPPP (Multilink PPP): The current method of combining one or more B channels to obtain more than the 64K conductivity generally used for data communications (IP, IPX, etc.).

Netblock: A block of IP numbers, typically a class C.

NT1 (Network Terminal 1): A device to convert the U interface to a S/T interface.

Out-of-Band Signaling: A method of signaling where the signaling information is transmitted on a separate channel from the data. An ISDN line uses a B channel to send data and a D channel to communicate with the switch to do call setup (i.e., dial the number).

PBX (Private Branch eXchange): A private telephone switch used by large corporations to provide access to their telephone network by the telco's telephone network.

Point-to-Point Number: Typically a set of two IP numbers; one for the remote end and one for the local end of the link.

POTS (Plain Old Telephone Service): The old analog phone lines we still use.

POTS Jack: The connection on back of a terminal adapter for the connection of an analog phone.

PRI (Primary Rate Interface): The method a telco uses to deliver the ISDN for multiline use. It is made up of 23 64K B channels and one 64K D channel in North America, 30 64K B channels and one 64K D channel in Europe. Typically, a PRI is used to a access router (ISP) or a company's PBX.

Provisioning: A telco term which defines the way a telephone line is set up and delivered. For example, a telco may provision a PRI line with only 6 active B channels of the 23 available.

S/T Interface: A four-wire method of supplying an ISDN line. Seven ISDN devices can be attached to an ISDN line provisioned with a S interface although only two may access a BRI at any one time. Most telcos in Europe deliver ISDN via the S/T interface. The S/T interface is sometimes called the S interface.

TA (Terminal Adapter): This is the device that connects to the ISDN line and provides the interface between the computer, network or analog phone to the ISDN network.

telco: Telephone company.

U Interface: A two-wire method of supplying an ISDN line. Only one ISDN device can be attached to ISDN line provisioned with a U interface. North American telcos deliver ISDN via the U interface.

SPID (Service Profile IDs): Used to identify what services are available to the attached ISDN device.