ADTRAN 1200070L1 - Manual (Page 172)

Glossary
156 Express XL/XLT User Manual 61200.070L1-1
Telnet
The TCP/IP standard protocol for remote terminal connection service. Telnet
allows a user at one site to interact with a remote timesharing system at anoth-
er site as if the user's terminal were connected directly to the remote machine.
TCP/IP
Transmission Control Protocol/Internet Protocol. A set of protocols devel-
oped by the Department of Defense to link dissimilar computers across many
kinds of networks.
twisted pair
Two wires twisted around each other to reduce induction (interference) from
one wire to the other. Several sets of twisted pair wires may be enclosed in a
single cable. Twisted pair is the normal cabling from a central office to your
home or office, or from your PBX to your office phone. Twisted pair wiring
comes in various thicknesses. As a general rule, the thicker the cable is, the
better the quality of the conversation and the longer cable can be and still get
acceptable conversation quality. However, the thicker it is, the more it costs.
2B+D
The Basic Rate Interface (BRI) in ISDN. A single ISDN circuit divided into two
64 kbps digital channels for voice or data and one 16 kbps channel for low
speed data (up to 9,600 baud) and signalling. 2B+D is carried on one or two
pairs of wires depending on the interface, the same wire pairs that today bring
a single voice circuit into your home or office. See ISDN.
23B+D
In ISDN, also known as the Primary Rate Interface. A circuit with a wide
range of frequencies that is divided in twenty-three 64 kbps paths for carrying
voice, data, video, or other information simultaneously. It bears a remarkable
similarity to today’s T1 link, except that T1 carries 24 voice channels. In ISDN,
23B+D gives twenty-three channels and one D channel for out-of-band signal-
ling. However, in T1, signalling is handled in-band. See ISDN.
two-wire circuit
A transmission circuit composed of two wires, signal and ground, used to both
send and receive information. In contrast, a 4-wire circuit consists of two
pairs. One pair is used to send and one pair is used to receive. All trunk cir-
cuits (long distance) are 4-wire. A 4-wire circuit delivers better reception, but
also costs more. All local loop circuits (those coming from a Class 5 central of-
fice to the subscriber’s phone system) are 2-wire, unless a 4-wire circuit is re-
quested.