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Glossary
ASCII
A binary code system which defines 128 characters using different combinations of 1s and 0s. ASCII
= American Standard Code for Information Interchange.
Asynchronous Data
Transmission where the characters are transmitted one at a time, starting with a start bit and ending
with a stop bit. About 90–95% of all serial data communications are asynchronous.
Baud
The number of data symbols transmitted every second. Often baud = bit/s. Sometimes a few data
symbols can represent several bits since different coding are used to compress data.
Buffer
A memory for storing data for a short time, e.g. until the receiver is ready.
Byte
A byte is a number of data bits (1s or 0s) which forms a character. Most often a character consists of
7 or 8 bits.
DCE
Describes which direction the signals in the RS-232/V.24 contact have. Modems are often DCE.
DCE = Data Communication Equipment.
DIN rail
An installation rail which is used in apparatus cubicles to set up different equipment on a simple way.
DIN = Deutsche Industri Norme.
DTE
Same as DCE but the signals are directed on opposite directions. Terminals, PC's and printers are
most often DTE. DTE = Data Terminal Equipment.
Data Compression and Error Correction.
V.42
CCITT's error correction protocol incorporating LAPM. If the V.42 connection fails then
usually MNP will be tried.
LAPM Link Access Procedure for Modems. An error correction method used in transmissions
via PTT modems.
MNP Microcom Networking Protocol. Several methods for error correction and data compres-
sion for PTT modems.
MNP 1:
MNP 2:
MNP 3:
MNP 4:
MNP 5:
MNP 10:
50
Asynchronous Protocol, half duplex.
Asynchronous Protocol, full duplex, Data is divided into blocks
(slower data rate).
Synchronous Protocol, full duplex. Data in blocks
(higher speeds with no errors).
Similar to 3, but with smaller data blocks allowing for faster data rates
with no errors.
Level 4 with data compression, gives about double the data rate.
Development of MNP5 with dynamic line monitoring and block size
adjustment, used on very bad lines (cellular phone connections).
6178-2203
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