asterisk users - Nov 2004 - How to connect Siemens Combiset to Asterisk - fxo or fxs ?

Hi,

I have Siemens combiset - it can gateway GSM phone to normal analog phone.
It has output where I can connect regulat analog phone.

How can I connect to combiset with Asterisk - via fxo or fxs ?

Thanks,

regards,

Robert.