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Chapter 4 Problems and Solutions 25
In the following table, “protocol” means error
correction and data compression. Note that the
first two lines in the table are likely to be the
most valuable.
Note 1: In the command strings shown in the table that
follows, the character 0 is zero, not the letter “O.”
To force the different communication speeds Type these commands and
press Enter
Negotiate speed and protocol
(default setting)
AT &F
Negotiate speed only, no protocol (not recom-
mended)
AT \N0
To force protocol
AT \N3
To force the different communication speeds
(i.e., maximum possible speed; actual speed
depends on line conditions and other factors)
Type these commands and
press Enter
Connect at 56000 bps (V.90)
AT +MS=V90,0
Connect at 56000 bps (K56flex)
AT +MS=K56,0
Connect at 33600 bps (V.34)
AT +MS=V34
Connect at 14400 bps (V.32bis)
AT +MS=V32B
Connect at 9600 bps (V.32)
AT +MS=V32
Note 2: You may find it helpful to include S95=44 in your
initialization string. This enables the responses
CARRIER (telephone line speed) and PROTOCOL,
as well as CONNECT (faxmodem-to-computer
speed).
Note 3: Some software allows these commands to be
added to the list of dial prefixes.
There are other configurations that can be forced as well.
If you need to select a particular configuration, use the AT
command strings shown below. You can always return to
the modem’s default configuration by typing AT &F and
pressing the Enter key. Remember that if you do this, the
modem will not have received the commands in your soft-
ware’s initialization string as it normally would. Using the
ATZ command overcomes this problem if you have saved
all of your setup parameters in nonvolatile memory. (To
save setup parameters in nonvolatile memory in AT termi-
nal mode: Type AT, followed by the parameter settings you
choose, followed by &W, and press Enter. For example, if
you type AT &C1 &D2 &W and press Enter, the &C1 and