AT&T DEFINITY 2500 series Network Manual page 328

GL-16
GLOSSARY
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listed directory number
(LDN)
local area network (LAN)
local exchange company
(LEC)
logical channel (or
circuit)
manual dialing
MEGACOM
800
MEGACOM
message-oriented
signaling (MOS)
modem
modem pooling
modular asynchronous
data unit (MADU)
modular processor data
module (MPDM)
modular trunk data
module (MTDM)
The listed number in a public directory for a communications system. An
incoming call to an LDN is usually answered by an attendant.
A networking arrangement specifically designed for a limited geographical
area. Generally, a LAN is limited in range to a maximum of 6.2 miles and
provides high-speed carrier service with low error rates. Common
configurations include star (including circuit switched), ring, and bus. See
also wide area network.
A company franchised to provide public intra-LATA (local access and
transport area) telephone service to subscribers within a defined
geographical area. Also called a local exchange carrier or local telephone
company.
A message slot on a digital communications link. A logical channel is one
of the logically independent elements of a data stream that is multiplexed
onto a single communications carrier.
Use of the dialing pad on a telephone to place a call by dialing each digit
individually.
AT&T's tariffed digital WATS offering for outward calling. See also 800
Service.
AT&T's tariffed digital 800-service offering for inward calling.
See DMI with message-oriented signaling.
A device that converts digital data signals to analog signals for
transmission over telephone circuits. The analog signals are converted
back to the original digital data signals by another modem at the other end
of the circuit.
A capability that provides shared conversion resources (modems and data
modules) for cost-effective access to analog facilities by data terminals.
When needed, modem pooling inserts a conversion resource into the path
of a data call. Modem pooling serves both outgoing and incoming calls.
A rack-mounted equipment unit housing up to eight plug-in asynchronous
data units (ADUs).
A processor data module (PDM) that can be configured to provide several
kinds of interfaces (RS-232C, RS-449, and V.35) to customer-provided
data terminal equipment (DTE). See also processor data module.
A trunk data module (TDM) that can be configured to provide several
kinds of interfaces (RS-232C, RS-449, and V.35) to customer-provided
data terminal equipment (DTE).