I have several discontinued Sierra Wireless MP775 mobile GSM/EDGE radio modems. These devices were originally installed in emergency vehicles to provide data and voice access along with GPS reporting. They have external RF connections for GSM/EDGE and GPS signals. The baseband side includes four wire audio, RS-232 serial, USB and some parallel digital I/O for panic switches etc. GSM voice connections are established by sending AT commands via the RS-232 serial or USB ports and utilizing a handset connected to the four-wire audio jack. Here is a link to the Sierra Wireless web pages for the MP775.
http://www.sierrawireless.com/support/mp775.aspx My interest comes in finding an inexpensive way to connect an Asterisk PBX or similar system to the PSTN via GSM when POTS and Internet service isn't available or is too costly to connect. In my case, I'm considering building a house at the end of a long unpopulated stretch of dead end road and the cost of trenching and cabling from the nearest telco POP is prohibitive. I would like to find a way to connect these modems to my network so they appear as a SIP FXS device. This would require a device generating/reading AT commands and passing baseband audio on the front end and SIP emulation on the backend. I'm sure there must be a way to do this with a pc but to minimize power consumption; I would prefer to use something like a small single board computer with a Geode processor. The latter, having multiple RS-232 and audio ports, ought to be capable of handling at least two of the MP775's. Has anyone seen any hardware, software or combination that would allow me to accomplish such an interface? Regards, George
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