[Asterisk-Users] Number of Zap channels in use

[Asterisk]

	Is there any way of knowing how many zap channels were in use at a 
particular time ?

We are getting a lot of "circuit busy" and "reorder" from our Sip phones 
when we're making outbound calls, and I'm convinced that we have not 
used our full complement of 30 channels (EuroIsdn 30).

I was just hoping that somewhere in the logs is a count of the number of 
"in use" channels.

Failing that, is there any way of capturing this information ?