I am new to raspberry pi and have been reading online about how people have successfully made VoIP gsm gateway using raspberry pi.
I wish to achieve the following:
1. A device which allows me to connect to my existing wifi network and allow to make calls wirelessly using the sim card on the raspberry pi.
Incoming calls are not important now although if all incoming calls can be defined by a simple pbx rule...ring ext1 for 4 rings if not answered ring ext2 for 4 rings and if not answered go to voice mail (voice mail also on the pi)
I have read people using Chan_dongle to connect a 3G dongle to make voice calls.
I was wondering of a GSM module can be used instead. like the SIM900
Please help and oblige. Also please share links if you can to this project so that I can read more and am able to achieve what I wish to.