[asterisk-users] Sip Node w/ 4 wire audio & AT command set call supervision

[George Bean]

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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