asterisk users - Sep 2003 - FW: Identify the channel ID within a SPAN

Hi list,

If I am using a T1 span to link with another PBX. for a particular call,
after the called party answers the call, how can I identify which channel of
the span is used for the call ??

The deplyoment is as follows:

caller---Asterisk ---- T1------- PBX---called party.

Assume I am using the dial,zap/g1/BYEXTENSION to let asterisk choose the
available channel, and once the call gets answer, can I know which channel
is used for the call, is there any application I can use to figure out when
the call is answered ?

Please advise.

Thanks,

George Lin