[Asterisk-Users] Detect line is busy with Zap?

[Ian Chilton]

Hi,

I have an FXO card connected to my phone line which works in Asterisk as
Zap/1.

Is there any way of detecting whether something else is on the line
before picking up on this channel?

For example, I dont want to pick up and dial out on the line if someone
is on it using another phone (which is connected directly to the line,
rather than through Asterisk).

Also, when an incoming call comes in, i've got this:

[incoming_pstn]
  exten => s,1,NoOp(${CALLERID} calling on Zap/1)
  exten => s,2,Wait,15
  exten => s,3,Answer
  exten => s,4,Voicemail(su1)
  exten => s,5,Hangup

I really want to wrap the Answer, Voicemail and Hangup commands in some
kind of if statement so if Asterisk didn't detect that the call had been
answered for any reason, it wouldn't answer the call if the line was
busy - otherwise it would click in and play the voicemail greeting over
the call which someone is conducting from a non-asterisk phone on the
line.


My zapata.conf looks like this:

[channels]
  context=incoming_pstn
  signalling=fxs_ks
  usecallerid=yes
  echocancel=yes
  echocancelwhenbridged=yes
  echotraining=yes
  rxgain=1.0
  txgain=0.0
  channel => 1


Thanks!

--ian