Archtek telecom 5634BIF, Руководство пользователя

Страница: 19 / 49

5634BIF User’s Manual
19
C
C
h
h
a
a
p
p
t
t
e
e
r
r
4
4
E
E
r
r
r
r
o
o
r
r
c
c
o
o
r
r
r
r
e
e
c
c
t
t
i
i
o
o
n
n
a
a
n
n
d
d
d
d
a
a
t
t
a
a
c
c
o
o
m
m
p
p
r
r
e
e
s
s
s
s
i
i
o
o
n
n
Your modem supports sophisticated MNP 1- 4 and V.42 error- correcting protocols. These
protocols ensure the transmission of error-free data
−
even over noisy, error- prone
telephone lines. Your modem also supports the V.42bis and MNP 5 data-compression
protocols, which maximizes data throughput and significantly reduces the time needed to
exchange data.
4.1 Error-correction protocols
Your modem includes two error-correction protocols:
•
MNP level 1 through 4
•
CCITT V.42
When these protocols are used, the two modems perform calculations on each "packet" of
data being exchanged and compare their values. If the values do not match, the receiving
modem requests the sending modem to re transmit the packet.
MNP is an acronym for M icrocom N etworking P rotocol. MNP detects and corrects errors
that occur when data is exchanged between two systems. Errors can result from
telephone- line noise and other signal distortions.
4.2 V.42
V.42bis the accepted international standard for error correction, ratified by ITU-T in
January 1990. It is generally felt that the handshake and protocol establishment process
of V.42 is superior to that MNP 4. Therefore, it will provide better initial connections on
poor quality telephone lines.
Moreover, while the effective data speed of V.42 and MNP 4 are almost identical over
noise-free telephone lines, V.42 provides significantly better performance than the ITU-T-
specified MNP4 over noisy telephone lines.
4.3 Configuring for auto-reliable operation
Auto-reliable operation is the modem's default configuration, so if you haven't given the
modem any
\N commands, it should already be in auto-reliable mode.
Auto-reliable mode lets your modem communicate with both MNP/V.42/V.42bis modems
and modems that do not use MNP/V.42/V.42bis :
1. Type AT\N3%C3 (Factory Setting)
2. Press the Enter key. Your modem responds with OK. When your modem originates or
answers calls, it will try to make a V.42bis/V.42 connection. If either or both fail, your
modem will try to make an MNP connection. If that fails, your modem will try to make a
normal connection that does not use error correction.