[Asterisk-Users] Picking a channel (FXO port or SIP) for outbound calls

[Rich Adamson]

> >From a post to this very thread just a few hours ago:
> 
> > exten => _9.,1,ChanIsAvail(Zap/1&Zap/2)
> > exten => _9.,2,Dial(${AVAILCHAN})
> > exten => _9.,102,NoOp
> > exten => _9.,103,Congestion 

Kind of a side question... what does ChanIsAvail actually check in the
above (loop attached, dialtone, or just that a call is/isn't in progress)?