Subj : COM  Ring Indicator
To   : borland.public.cpp.borlandcpp
From : Jack Sawatzky
Date : Fri Jul 15 2005 02:53 pm

The ring indicator signal  (RS232,  DB9 pin 9)  is the only unused signal
available in a system which I am upgrading.  My circuit can switch it
between +8 and -8 volts, but I have not been able to detect it from my
software.  I tested the following code extensively for errors  (invalid
handle, etc.), and all reports where successful.  But it always shows
the same result, whether the signal is on or off.

       hcom=CreateFile("COM3", GENERIC_READ, 0, NULL, OPEN_EXISTING,
        FILE_ATTRIBUTE_NORMAL, NULL);

        GetCommModemStatus(hcom, &ring);                              
          if(ring && MS_RING_ON ) { indicate  }

I looked at  SetCommState(), but was unable to see anything that
related to the ring indicator.
Can you tell me how to access this signal?

Thanks.

.