AT&T MERLIN LEGEND Data Manual page 140

Glossary
DIP (dual in-line package) switch
A switch on a 400EM module used to select the signaling format for tie-line transmission. DIP switches are also used on other
equipment for setting hardware options.
direct facility termination (DFT)
A central office (CO) line/trunk that terminates directly on one or more telephones; in PBX mode a DFT cannot be part of a
trunk pool.
direct inward dialing (DID)
A service that transmits the called station number to the communications system from the central office (CO) and routes
incoming calls directly to the called station, calling group, or outgoing trunk pool, bypassing the system operator.
Direct Station Selector (DSS)
A 60-button adjunct that enhances the call-handling capabilities of an MLX-20L telephone or MLX-28D telephone when used
as an operator console.
display buttons
The buttons on an MLX display telephone used to access the telephone's display.
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
signals, each composed of two voice-band frequencies.
E
E and M signaling
Trunk supervisory signaling, used between two communications systems, in which signaling information is transferred
through two-state voltage conditions (on the E and M leads) for analog applications and through two bits for digital
applications. Used in tie trunks.
EIA (Electronic Industries Association)
A trade association of the electronics industry that establishes 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 (ESF) format
A framing format consisting of individual frames of 24 eight-bit slots and
superframe. See also D4 framing format.
GL-6
1 signal bit (193 bits) in a 24-frame extended
12 distinct