ZyXEL Communications Omni 56K USB Lite User Manual page 37

STANDARD
V.32bis
V.32
V.32 uncoded
V.32
V.23
V.23
V.22bis
2400 Ans
V.22 (BELL 212)
2400 Ans
V.21 (BELL 103)
Error Control
Error control keeps the modem data link error-free by detecting and re-transmitting erroneous data. The
Omni 56K USB Lite supports both MNP and V.42 error control protocols. The MNP protocol was an
industry standard developed and licensed by Microcom, Inc. The Omni 56K USB Lite supports level 4 and 3
error control protocols, commonly denoted as MNP4 and MNP3.
V.42 is a standard developed by CCITT (Consultative Committee for International Telephony and
Telegraphy). V.42 supports both LAPM (Link Access Procedure for Modems) and MNP4. A V.42
handshaking tries an LAPM connection first, and if not successful, it tries MNP4.
Data Compression
In the modem, the data compression is activated in an attempt to reduce the number of bits actually sent. The
receiving modem applies these techniques in reverse to recover the actual data from the compressed data
stream.
The Omni 56K USB Lite supports both V.42bis and MNP5 data compression protocols. Data compression
needs an error-free data link to work correctly, otherwise the corrupted compressed data stream ruins the
decompression process. MNP5 is used with MNP4 error control and V.42bis is used with V.42 error control.
The compression efficiency of V.42bis is generally higher than that of MNP5. In some cases, V.42bis can be
50% to 100% higher and in other cases it is just slightly higher. In general, it is about 50% more efficient.
Specifications and Functional Description
BIT RATE
[BPS]
4800
9600
9600
4800
1200/75
600/75
2400
1200
300
BAUD RATE
[BAUD]
2400
2400
2400
2400
1200/75
600/75
600
600
300
Omni 56K USB Lite
MODULATION
FREQUENCY [HZ]
1800
32-TCM 1800
16-QAM 1800
4-DPSK 1800
FSK
FSK
16-QAM 1200 Call
4-DPSK 1200 Call
FSK
CARRIER
3-5