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Glossary
Glossary-73810-A2-GB30-20 November 1996
modem (Modulator/DEModulator). A device that transforms signals from digital to analog form
and vice versa.
modulation The process of varying some characteristics (usually amplitude, frequency, and/or phase)
of a carrier wave to form data transmissions.
network A communications circuit.
network address The customer-assigned diagnostic address of a tributary modem.
NIM Network Interface Module. The interface provided, up to two per carrier, for the public
switched telephone network (PSTN) used by Model 381
1 dial modems.
NMS
Network Management System. A set of diagnostic and configuration management tools
for a data communication network, consisting of software programs and dedicated
computer hardware.
off-hook
A telephone or modem is being used.
on-hook
A telephone or modem is not being used.
Originate mode The modem is in a state where it is ready to transmit a call. In a dial network, it is the
modem that makes the call. In a leased-line network, it is one of two sides of the network
that is selected to be the originating modem.
parity A way of checking data accuracy by counting the number of bits that have a value of
one.
PBX Telephone switching equipment (Private Branch Exchange) dedicated to one customer
. A
PBX connects private telephones to each other and to the public dial network.
permissive interface A dial modem operating mode characterized by a fixed output power level of –9 dBm. It
is one of two possible modes of operation for modems connected to dial lines (see
programmable interface).
physical address The diagnostic address of a control modem derived from its location in the carrier: its
carrier and slot number.
power-up self-test
A test that checks most hardware components when the modem is powered-on.
product code A three-digit code indicating the modem’
s highest VF data rate.
programmable interface A dial modem operating mode characterized by an output power level (–12 to 0 dBm) set
by a programming resistor in the jack. It is one of two possible modes of operation for
modems connected to dial lines (see permissive interface).
protocol The rules for timing, format, error control, and flow control during data transmission.
PSTN Public Switched T
elephone Network. A network shared among many users who can use
telephones to establish connections between two points. Also known as dial network.
pulse dialing One of two dialing methods, in which telephone numbers are sent as pulses (brief
changes in voltage or current intensity) across the telephone line. Rotary telephones use
pulse dialing.