Revisiting A GSM Interface For Your Asterisk Server

Some time ago @Boxdog pointed me to a uCPBX in Bulgaria. They are reselling various small Asterisk systems based upon the Astfin project. They have a few variations on the IP04, including an 8 port variant (IP08 = 8 FXOs) as well as 1 or 4 port BRI capable versions.

ucpbx-astfin-br4-back

The design of the base system supports adding interface ports through the use of little daughter cards. I believe that their daughter cards are compatible with Digium’s TDM-400P card. The cards even use the standard DAHDI driver making installation especially easy.

ucpbx-gsm-cardThe same company also offer a GSM trunk interface that they call simply GSM1. It is also in the form factor of a daughter card for the TDM-400P. That means that it can be added directly to the IP04 appliance, or to an existing TDM card in a more traditional server host. It looks like a TDM-400P card can host two of the GSM interfaces.

This little GSM card is being offered for 150 Euro which is around$220 USD. At that price it’s marginally cheaper than the Portech MV-370 that I bought last year, presuming that you already have the TDM-400P card. If you have to buy both then the Portech box is cheaper.

There’s a certain elegance about having the GSM interface right inside your Asterisk system. No extra power supply or network wiring to worry about. That makes for a very clean, reliable installation.

I still think that a cellular gateway is a solid approach to having an emergency trunk when you don’t have any POTS lines to your location. You can use it to provide 411 and 911 service, and leverage that offer of a zillion free “mobile-to-mobile” minutes when calling to other cell phones.

Of course, I’ve written about all this before.

How To: Add A Cellular Trunk To Your VOIP System

  • This little card looked pretty interesting, but I’ll say I was disappointed that it had no way to send/receive SMS or MMS messages. The Portech at least has some out-of-band methods to send text (though they should convert to SIP messaging.) SMS is really an indispensable feature if you have a GSM channel – it doesn’t make sense to have a system that doesn’t allow integration with Asterisk for short messages.