USRobotics V.34 - Manual (Page 174)

COURIER HIGH SPEED MODEMS
Synchronous Operations F-9
Commands and Result Codes NOT Supported
• CRI (Call request with identification number)
• PRI (Program identifier)
• RLI (Request list of identification numbers)
• RLD (List of delayed call numbers)
Hanging Up
Since the modem cannot accept commands once it is connected
in synchronous mode, you cannot use the ATH (hang up)
command or the +++ escape sequence.
The only way for the modem to disconnect is to drop its DTR
signal. This is normally done with software. However, if the
modem is initially set to S32=6 when it is in asynchronous
mode, the modem will reset when the voice/data switch is
pressed, thus dropping DTR.
Returning to Asynchronous Mode
Once you've completed a communication session, you can
switch between synchronous and asynchronous modes by
flipping DIP switch 10 OFF (factory settings, asynchronous
mode) and then ON (NVRAM settings, synchronous mode if
the modem is set to &M6 or &M7).
The modem cannot switch between synchronous and
asynchronous while a call is connected.
ONLINE SYNCHRONOUS REQUIREMENTS
Although personal computers do not usually support
synchronous communications, they can be dedicated to do so.
If you have a personal computer you must find out what
hardware and software you need before setting the Courier for
synchronous calls.