HOW TO connect GSM-gateway to PBX

Hi
I am very new to PBX so please go easy on me if I miss something.
I got Fritzbox to which I connect GSM-gateway through PSTN port.
So my question is
Is it possible to register as a truck or incorporate into my PBX my gsm gateway or pstn line.
So for example I would like to make call to mobile from other extensions e.g. xlite on other computer.
thanks for any help in advance

RE: HOW TO connect GSM-gateway to PBX

Getting the Fritz!Box to allow any of its' trunks to be used from another SIP User Agent is not easy.

However, I have recently located a very informative guide on how to enable use of the Fritz!Box VoIP line from a soft-phone. I haven't had the chance to try it yet, and it's not for the faint at heart.

I am not sure if it will work for the PSTN port though. Anyone else with an opinion?

RE: HOW TO connect GSM-gateway to PBX

Thank you for reply
Well I can use spa3120 for this purpose too
can I use my gsm gateway with pbxes than?

RE: HOW TO connect GSM-gateway to PBX

i am using spa-3102 for the same, i use subpbxes function.

1) create sub pbxes username and passord.
2) use this userid and password in pstn tab in 3102
3) then create outbound route to use this sub pbxex to make calls through spa 3102

i have been using this and its works perfectely.

RE: HOW TO connect GSM-gateway to PBX

Thanks a lot
but I amusing for outgoing calls (callthru) as well as incoming diverted to my sip.
Will this work both ways if I set up to Routing correctly?