Westermo TD-22 - Manual (Page 46)

47 6177-2203
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. In local data communications, baud = bit/s.
In telecommunication, each symbol may encode several bits.
Buffer
A memory for storing data for a short time, e.g. until the receiver is ready
Byte
A character comprising binary numbers, e.g. an ASCII character which consists of 7–8 data bits, each
corresponding to an alphanumerical character.
DCE
Data Communication Equipment. Like a Modem, protocol converter or line driver.
DIN rail
Deutsche Industri Norme standard mounting for the installation of equipment in an apparatus cubicle.
DTE
Data Terminal Equipment like PC,s, terminals and printers.
Data Compression and Error Correction
V.42
CCITT’s error correction protocol incorporating LAPM. If the V.42 connection fails then 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 compression for PTT
modems.
MNP 1: Asynchronous Protocol, half duplex.
MNP 2: Asynchronous Protocol, full duplex, Data is divided into blocks (data rate actually slows).
MNP 3: Synchronous Protocol, full duplex. Data in blocks (higher speeds with no errors).
MNP 4: Similar to 3, but with smaller data blacks allowing for faster data rates with no errors.
MNP 5: Level 4 with data compression, gives about double the data rate.
MNP 10: Development of MNP5 with dynamic line monitoring and block size adjustment, used on
very bad lines.
ARQ
Automatic Repeat reQuest. When incorrect data is detected a modem a request to retransmit the data
is made to the remote modem.