User guide

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Chapter 5 - AT Commands
Error Correction and Data Compression Commands
You can configure modems to any of three different V.42 modes of operation (with or without compression):
non-error correction, auto-reliable, and reliable modes. You also can turn data compression on or off.
\Nn Error Correction Modes
n = 0, 1, 2, 3, 4, 5, or 7
Default: \N3
Select the modem’s error correction mode using the \N command.
\N0 disables the modem’s V.42 error correction capabilities, and the modem functions as a
non-error correction modem with data buffering. This is the same as &Q6, described earlier in
this chapter.
\N1 causes the modem to function in direct mode.
\N2 enables reliable mode, in which the modem uses its V.42 error correction capabilities for
all transmissions. In reliable mode, the modem must be connected to a modem with the V.42
MNP protocol.
\N3 enables auto-reliable mode. During the handshaking procedures at the start of the online
connection, the modem queries whether the other modem is using V.42 error correction. If the
modem determines that the other modem is using V.42, it switches itself into reliable (V.42)
mode and enables error correction. If it determines that the other modem is not using V.42, the
modem remains in non-error correction mode. (This is the same as \N5 and \N7.)
\N4 enables reliable mode, in which the modem uses its V.42 error correction capabilities for
all transmissions. In reliable mode, the modem must be connected to a modem with a V.42
protocol (MNP or LAP-M).
The V.42 standard includes MNP Class 3 and 4 and LAP-M error correction methods.
\N5 enables auto-reliable mode. During the handshaking procedures at the start of the online
connection, the modem queries whether the other modem is using V.42 error correction. If the
modem determines that the other modem is using V.42, it switches itself into reliable (V.42)
mode and enables error correction. If it determines that the other modem is not using V.42, the
modem remains in non-error correction mode. (This is the same as \N3 and \N7.)
\N7 enables auto-reliable mode. During the handshaking procedures at the start of the online
connection, the modem queries whether the other modem is using V.42 error correction. If the
modem determines that the other modem is using V.42, it switches itself into reliable (V.42)
mode and enables error correction. If it determines that the other modem is not using V.42, the
modem remains in non-error correction mode. (This is the same as \N3 and \N5.)
%Cn Data Compression
n = 0 or 1
Default: %C1
The %C command allows you to disable data compression. Data compression is normally
enabled.
%C0 disables V.42bis/MNP 5 data compression.
%C1 enables V.42bis/MNP 5 data compression.