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Glossary
61202.029L2-1 ISU 128 User Manual 125
ISDN
Integrated Services Digital Network. A network architecture that enables end-to-end
digital connections. The network supports diverse services through integrated access
arrangements and defines a limited set of standard, multipurpose interfaces for
equipment vendors, network providers, and customers. Interworking with a public
switched telephone network is retained.
LATA
Local Access and Transport Area. One of 161 local telephone serving areas in the
United States, generally encompassing the largest standard statistical metropolitan
areas. Subdivisions established as a result of the AT&T divestiture that now
distinguish local from long distance service. Circuits with both end-points within
the LATA (intraLATA) are generally the sole responsibility of the local telephone
company, while circuits that cross outside the LATA (interLATA) are passed on to an
interexchange carrier.
loopback
A diagnostic procedure where data is sent to the device being tested, and the output of
the device is fed directly back to its input, looped around, and the returning data is
checked against that which was sent.
message
The Layer 3 information that is passed between the CPE and SPCS for signalling.
multiplexing
The combining of multiple data channels onto a single transmission medium. Any
process through which a circuit normally dedicated to single user can be shared by
multiple users. Typically, user data streams are interleaved on a bit or byte basis
(time division) or separated by different carrier frequencies (frequency division).
multipoint circuit
A circuit consisting of three or more stations connected directly electrically.
narrowband ISDN
A collective term for BRA and PRA at speeds up to 1.544 Mbps.
non-ISDN line
Any connection from a CPE to a SPCS that is not served by D-Channel signalling.
non-ISDN trunk
Any trunk not served by either SS7 or D-Channel signalling.
NT1
Network Termination 1. A unit that provides physical and electromagnetic
termination of the U-interface 2-wire transmission line, converts between Layer 1
formats used at the U- and T- reference points, and performs some maintenance
functions.