User`s guide

40 56K Message Modem

half duplex

Signals will flow in both directions, but only one way at a time. In

microcomputer communications, may refer to activation of the online

local echo, which causes the modem to send a copy of the transmitted

data to the screen of the sending computer.

Hertz, a frequency measurement unit used internationally to indicate

cycles per second.

ITU-T (International Telecommunications Union)

An international organization that defines standards for telegraphic and

telephone equipment. For example, the Bell 212A standard for 1200-

bps communication in North America is observed internationally as ITU-

T V.22. For 2400-bps communication, most U.S. manufacturers

observe V.22 bis. The initials ITU-T represent the French name. In

English it is known as the International Telegraph and Telephone

Consultative Committee.

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 erred 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.