So far I have come to a dead end. I have decided to go ahead, hook up
the cellular modem to the phone, tap off the lines at the phone, convert
the levels back to RS232 and see if I can decipher what they are sending
to the phone. I checked out the siemens site and all they had was the
GSM phones but they will not work here in the states, or at least not in
this part of the country. Thanks to all who responded on and off the
list. As a temporary fix, I will just make connections to the keypad pcb
directly and control it as if the buttons were being pushed. by using a
standard plugin arrangement, I can build up a batch of phones of
different brands and models and the techs can just unplug the defective
unit and plug in a new one in case of failure.Not the most sophisticated
method, but simple and easy to control the phone. They will not be
accessible to anyone except technicians so that won't really matter. I
had hoped to find a simple serial control method so as not to have to
modify the phones in any way. Maybe after studying the signals passed
back and forth to the cellular modem and the phone.
Thanks a bunch for the suggestions on and off the list guys.

ckchan wrote:
>
> Greetings,
>
> > I have the data cable for the Nokia but I don't need and cannot use a
> > modem for this application. I have a cellular modem (U.S.Robotics)that
> > will connect to the Nokia (or whatever phone with proper cable)but it
> > uses a pc and I need to do this with a small processor(PIC). From all
> > the data I have found, it uses a proprietary protocol to send commands
> > to the phone. Thanks for thinking about me though.
>
> Maybe you can try to send some standard AT command most GSM modem
> supported. In previous post, information from the siemens GSM module might
> be usefull. good luck.
>
> regards,
> ckchan
>
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