THIS QUESTION IS BEING CLOSED
I have a phone dialer as part of a larger app. The phone dialer is modeled after an example Dialer program that came from Microsoft. The Microsoft dialer example stops/cancels/ends the dialing operation by sending an ATH + Carrage Return followed immediately by closing the comm port. (I assuming this may be the problem, but I don't really know what's causing it.)
Even though this does not allow the modem to complete the hangup and report OK, it works on most modems except US Robotics.
Users with US Robotics modems report that after dialing one number the modem locks up. They can't dial another number. Getting out of the program and back in doesn't help. Some report they must reboot to reset the modem. Others report going into any other program that uses the modem resets it. I have tried sending all the commands I can think of to reset it but without success.
What are the other comm. programs doing that is effective reseting the modem? Or, what does Windows do during a power on restart that resets it?