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&D n
Data Terminal Ready Control{xe "RS-232C:controls"}{xe "AT
commands:&D"}{xe "DTR signal:control of"}{xe "Data Terminal Ready
Control command"}
n = 0, 1, 2, or 3
Default: &D2
The Data Terminal Ready (DTR) signal on pin 20 of the RS-232/V.24{xe "RS-
232C"} interface must be high, or "on," in order for the modem to operate. A high
DTR signal tells the modem that th e computer i t is connected to i s rea dy to
communi cate th rough th e modem.
The DTR signal can also be used to cause the modem to reset to its default parame-
ter{xe "parameters:default"}s, as if you had given the modem an ATZ command.
&D0 (or &D) causes the modem to ignore the DTR signal and treat it as always on.
&D1 causes the modem, if in online data mode, to enter command mode, issue an OK
and remain connected when the DTR drops.
&D2 causes the modem to hang up when DTR drops while the modem is in online
data mode.
&D3 causes the modem to reset when DTR drops {xe "DTR signal:control of"}. It
will also hang up if it is online.
&S n
Data Set Ready Control{xe "RS-232C:controls"}{xe "AT
commands:&S"}{xe "Data Set Ready Control command"}{xe "DSR
signal:control of"}
n = 0 or 1
Default: &S0
Use the &S command to control the state of the Data Set Ready (DSR) signal on the
RS-232/V.24{xe "RS-232C"} interface. Normally, DSR follows CD. You can force
the signal high or allow it to act normally.
&S0 forces DSR high (on).
&S1 allows DSR to act normally, that is, to follow CD.
Error Correction and Data Compression Commands
You can configure a modem to any of three different V.42{xe "V.42"} modes of
operation (each mode can be with or without compression). They are the non-error
correction, auto-reliable, and reliable modes. You can also turn data compression on
or off.
\N n
Error Correction Modes{xe "AT commands:\N"}{xe "Error Correction
Modes command"}{xe "error correction:selecting"}
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{xe "V.42"} error correction{xe "error
correction:disabling"} capabilities, and the modem functions as a non-error
CommPlete Communications Server
3 AT Commands
29
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