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G
LOSSARY
7-6
LAPM
Link Access Procedure for Modems. An error-
control
protocol defined in ITU-T recommendation
V.42 . Like the MNP protocols, LAPM uses cyclic
redundancy checking ( CRC ) and retransmission
of corrupted data ( ARQ ) to ensure data reliability.
local echo
A modem feature that enables the modem to display
keyboard commands and transmitted data on the
screen. See command En.
MNP
Microcom Networking Protocol, an error-control
protocol developed by Microcom, Inc., and now in
the public domain. There are several different MNP
protocols, but the most commonly used one ensures
error-free transmission through error detection
(
CRC ) and retransmission of flawed frames .
modem
A device that transmits/receives computer data
through a communications channel such as radio or
telephone lines. It also changes signals received
from the phone line back to
digital signals before
passing them to the receiving computer.
nonvolatile memory (NVRAM)
User-programmable random access memory whose
data is retained when power is turned off. On the
U.S. Robotics modem, it includes four stored phone
numbers and the modem settings.
off/on hook
Modem operations that are the equivalent of
manually lifting a phone receiver (taking it off-
hook) and replacing it (going on-hook).
online fall back/fall forward
A feature that allows high-speed, error-control
modems to monitor line quality and fall back to the
next lower speed in a defined range if line quality
diminishes. As line conditions improve, the
modems switch up to the next higher speed.
originate mode
The mode used by your modem when initiating an
outgoing call to a destination modem. The
transmit/receive frequencies are the reverse of the
called modem, which is in
answer mode .
parity
A simple error-detection method that checks the
validity of a transmitted
character . Character