[Freeswitch-users] how to check if freetdm channel in use

Hi people! I have a A200 board running, and I want to figure out in the dialplan through it's variables if the channel is in use or not that if a second call comes inside to be routed somewhere else, let us say to my voicebox. I want to check if freetdm/1/1 is busy at the moment.... Has anyone an idea how to accomplish this?! Tamer