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Standard
BPS rate
(+/-0,01%)
K56flex
56,000 - 32,000
V.34bis
33,600/31,200
V.32bis
14,400
V.32bis
12,000
V.32bis
7,200
V.32
9,600
V.32 uncoded
V.32
4,800
V.29*
9,600
V.29*
7,200
V.29*
4,800
V.27bis*
4,800
V.27bis*
2,400
V.26bis*
2,400
V.23
1,200 / 75
V.23
600 / 75
V.22bis†
2,400
V.22†
1,200
V.21
300
BELL 103
300
G3 FAX
Implemented according to T.30, V.17,V.29 and V.27ter.
Error Control
Error control keeps the modem data link error-free by detecting and re-transmitting
erroneous data. ZyXEL modems support both MNP and V.42 error control protocols.
The MNP protocol was an industry de facto standard developed and licensed by
Microcom, Inc. ZyXEL modems support level 4 and 3 error control protocols,
commonly denoted as MNP4 and MNP3. V.42 is a standard developed by ITU-T. V.42
supports both LAPM (Link Access Procedure for Modem) and MNP4. A V.42
handshake will try an LAPM connection first, and if not successful, it will try MNP4.
The error control (MNP4, LAPM) methods in modem to modem connections are based
on techniques utilized by both modems. They are explained below.
CRC (Cyclical Redundancy Check) Error Detection
At the end of every data block, a 16-bit number CRC, which is calculated through a
polynomial function, is sent. The receiving modem receives the block, calculates its
own CRC through the same polynomial function, then compares the numbers. If it
matches the received CRC, everything is all right. If not, an error(s) has occurred
somewhere in the block. The modem checks every block received for error(s).
9,600
Baud rate
Modulation
(+/-0,01%)
multiple
PCM
2,400
TCM
2,400
128-TCM
2,400
64-TCM
2,400
16-TCM
2,400
32-TCM
2,400
16-QAM
2,400
4-DPSK
2,400
16-QAM
2,400
8-QAM
2,400
4-DPSK
1,600
8-PSK
1,200
4-DPSK
1,200
4-DPSK
1,200 / 75
FSK
600 / 75
FSK
600
16-QAM
600
4-DPSK
300
FSK
300
FSK
Advanced Data Communications 21
Carrier Freq
[Hz]
multiple
1,800
1,800
1,800
1,800
1,800
1,800
1,800
1,700
1,700
1,700
1,800
1,800
1,800
1,200 Orig.
2,400 Ans.
1,200 Orig.
2,400 Ans.
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