regarding gsm

Can you please send me some sites regarding details about GSM/GPRS

well one such popular modem industrial is wavecom...
you can join the forum ..
search wavecom Open AT development forum on google...
neways we have a very good person in shailesh nayak to help u out he has done enough on gsm to help u out!! :-)

here is the link
www.wavecom.com/forum

In order to fulfill your customer requirements, you need to build a product
that consists of 3 main functions.
1. Subscriber line interface (or 2 to 4 wires interface) - to do the interface
between desktop phone and your product
2. DTMF decoder / encoder - to detect DTMF signals sent by the desktop
phone
3. uP (Microprocessor) - to communicate with WM module according to
DTMF inputs
A copy of sample block diagram is shown as below for your reference.
As described from the above diagram, uP (Microprocessor) controlled the
whole system; if detect DTMF signal, uP will off the audio path, and send
DTMF command to module, and for audio it will direct to module audio path
via subscriber line interface unit. Also, you may consider to use the following
components in your product design.




Subscriber line Interface (2 to 4 wires system): STLC3055
DTMF decoder/encoder: Mitel MT8888CS
Please note that the purpose of the above diagram is for reference only.
Hope this will help you out!