Call progress on FXO port for later bridging

Hi!, I was wondering if this is possible to achieve:

Upon reception of an incoming call, dial some extensions of the dialplan and, at the same time, make a call through an FXO port (that happens to be attached to a GSM line) in order to reach a cell phone.

SHOULD the cell phone get answered, the call gets bridged to the one ringing the other extensions, and of course ringing gets finished.

I’m not quite an expert in Asterisk (yet :smile:), but this should be a good approach for cheap (no VoIP GSM gateways involved) reaching a GSM phone, as if it was another extension of the PBX.

Any light on?


It should not be hard at all. All you have to do is dial both extensions at once. The only issue you may have if using an FXO is that as soon as asterisk grabs the line it may show it as answered. You may want to pay a developer to set up Zaptel that it only shows answerd on an FXO if it was actually picked up at the other end (you can tell by the polarity of the wires - I do not know much about this).


what you say is correct. Asterisk thinks the FXO outgoing call got answered as soon as it gets dial tone, instead of waiting the cell phone to actually off-hook.

I’ll try the approach trying to detect polarity changes (hope the GSM-PSTN gateway I got here does or can do it…)

Thanks for the clue!