Westermo TD-34 - Manual (Page 53)

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9. 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 sym-
bols 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 ITU-T’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 transmis-
sions 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
(slower data rate).
MNP 3: Synchronous Protocol, full duplex. Data in blocks
(higher speeds with no errors).
MNP 4: Similar to 3, but with smaller data blocks 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 (cellular phone connections).
ARQ Automatic Repeat reQuest.When incorrect data is detected a request to retransmit
the data is made to the remote modem.
V.42bis. Data Compression technique used by modems rather than MNP5, because it offers
better transmission on already compressed data.