AT&T MERLIN LEGEND Installation & Maintenance Manual page 695

Glossary
door answering unit
A device that is connected to
a basic telephone jack and
used at an unattended station
or front desk.
DS0 (Digital Signal 0)
A single 64-kbps voice or
data channel.
DS1 (Digital Signal 1)
A bit-oriented signaling (BOS)
interface that multiplexes 24
64-kbps channels into a
single 1.544-Mbps stream.
dual-tone multifrequency
(DTMF) signaling
Touch-tone signaling from
telephones using the voice
transmission path. The code
for DTMF signaling provides
12 distinct signals, each
composed of two voice-band
frequencies.
E
E and M signaling
Tie-trunk supervisory
signaling, used between two
communications systems, in
which information is
transferred through two-state
voltage conditions (on the E
and M leads) for analog
applications and through two
bits for digital applications.
GL-10 Glossary
EIA (Electronic Industries
Association)
A trade association of the
electronics industry that sets
electrical and functional
standards.
electronic switching system
(ESS)
A class of modern switching
central office (CO) systems
developed by AT&T in which
the control functions are
performed principally by
electronic data processors
operating under the direction
of a stored program.
endpoint
The final destination in the
path of an electrical or
telecommunications signal.
expansion carrier
A carrier added to the control
unit when the basic carrier
cannot house all the modules
needed. An expansion carrier
houses a power supply
module and up to six
additional line/trunk and
station modules.
extended superframe format
(ESF)
A framing format consisting of
individual frames of 24 eight-
bit slots and 1 signal bit (193
bits) in a 24-frame extended
superframe. See also D4
framing format.