[asterisk-users] GSM Gateway behind SIP ATA?

[Remco Barendse]

I have an analog GSM Gateway that is connected to a normal SIP ATA device.

Basically what it does is this : when you call the extension nr. of the 
SIP ATA port, the GSM Gateway will pick up the phone and presents a (new) 
dial tone, and then dials whichever DTMF tones it received. The SIP ATA ia 
a Grandstream HT286.

I would like to use the GSM Gateway to route my outbound cellular calls, 
how do i do this in Asterisk? Basically Asterisk should dial the extension 
number and then send required number as DTMF tones to the Gateway through 
the ATA.

I am using FreePBX, which allows me to create a custom trunk for the 
outgoing calls. Hope this could work :)