Ok, this is probably an easy question:
Say I have my kamailio server set up and all of my voip clients are gleefully calling each other... but now I want to connect them to the PSTN.

Can I set up kamailo to trunk calls using a few grandstream gateways? or is Asterisk neccesary?

Sorry if the answers out there, but I haven't found anything that answered the question directly.
I'm a linux admin, but I'm new to PBX's and the like. I've installed kamailio in the past using instructions specific to that situation, but haven't configured trunking (or I didn't recognize thats what it was)

references to howtos or tutorials would also be greatly appreciated

Thanks for your help,
Jared Martin