[Asterisk-Users] Instant hangup on busy Zap channel.

[Richard Scobie]

A call is placed via IAX2 from one asterisk to another, to a TDM400 
channel whose extensions.conf entry is

exten => 502,1,Dial(${COLIN})
exten => 502,2,Congestion

If  this channel is already busy when called, the call is instantly 
hungup, without the caller hearing the congestion tone.

The log from the callers asterisk shows:

 -- Executing Dial("Zap/1-1", "IAX2/192.168.3.223/502|30") in new stack
    -- Called 192.168.3.223/502
    -- Call accepted by 192.168.3.223 (format 4)
    -- Format for call is 4
    -- IAX2[pbxak]/2 is circuit-busy
  == Everyone is busy at this time
    -- Hungup 'IAX2[pbxak]/2'
    -- Executing Hangup("Zap/1-1", "") in new stack
  == Spawn extension (incoming, 502, 2) exited non-zero on 'Zap/1-1'
    -- Hungup 'Zap/1-1'

Is this expected behavior, or have I missed something in the configuration?

Thanks,

Richard