AC75 AT Command Set
4. Serial Interface Control Commands s
AC75_ATC_V01.002 Page 105 of 569 10/30/06
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4. Serial Interface Control Commands
The AT Commands described in this chapter allow the external application to determine various settings related
to the AC75's serial interface.

4.1 AT\Q Flow control

Syntax
Parameter Description
[0](&F) Disable flow control
1 XON/XOFF software flow control
2 Only CTS by DCE (TA)
3 RTS/CTS hardware flow control
Recommended for the following procedures: incoming or outgoing data calls,
fax calls, MUX mode.
Often, the initialization routine of Fax programs includes enabling RTS/CTS
handshake, eliminating the need to issue AT\Q3 once again.
Notes
• When using XON/XOFF flow control (AT\Q1) in online mode, +++ should not be used while the data trans-
mission is paused with XOFF. Before entering the command mode with +++ the paused transmission should
be resumed using the XON character.
• For compatibility reasons, the AT\Q command can be used in Multiplex mode, though the settings will not
take effect. However, be aware that whenever you use the AT\Q write command in Multiplex mode and then
save the current configuration to the user profile with AT&W, the changed AT\Q setting will become active after
restart.
•With AT+IFC, flow control can be set separately for each data direction, while AT\Q applies to both directions.
The two commands influence each other, i.e. settings made with AT\Q apply to AT+IFC and, vice versa,
AT+IFC changes the AT\Q setting.
Exec Command
AT\Q[<n>]
Response(s)
OK
If RTS/CTS flow control is not supported by interface and <n> is 2 or 3:
ERROR
Reference(s) PIN ASC0 ASC1 USB MUX1 MUX2 MUX3 Charge 4Last
SIEMENS - + + - ± ± ± - + -
<n>(num)(&W)(&V)