Glossary
Glossary-9
3830-A2-GB91-20
November 1996
modulation
The process of varying some characteristics
(usually amplitude, frequency, and/or phase) of a
carrier wave to form data transmissions.
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).
power-up self-test
A test that checks most hardware components
when the modem is powered-on.
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).
product code
A three-digit code indicating the modem’s highest
VF data rate.
protocol
The rules for timing, format, error control, and
flow control during data transmission.
