B.20. Congestion()

Indicates congestion (insufficient resources available) on the channel.
Congestion([timeout])
Indicates congestion on the channel and waits until the caller hangs up or until the specified timeout timeout has expired.
This application indicates congestion in the system but does not indicate this to the caller. Should you wish to notify the caller, use Playtones(congestion).
Returns -1.
; for Caller ID is 888-555-8701, always signal congestion:
exten => 123,1,GotoIf($[${CALLERID(num)} = 8885558701]?10)
exten => 123,n,Playtones(congestion)
exten => 123,n,Congestion(5)
exten => 123,n,Hangup()
exten => 123,10,Dial(Zap/1)

Note

Internal help for this application in Asterisk 1.4:
  -= Info about application 'Congestion' =- 

[Synopsis]
Indicate the Congestion condition

[Description]
  Congestion([timeout]): This application will indicate the congestion
condition to the calling channel. If the optional timeout is specified, the
calling channel will be hung up after the specified number of seconds.
Otherwise, this application will wait until the calling channel hangs up.
diff output to internal help in Asterisk 1.2:
8c8
<   Congestion([timeout]): This application will indicate the congestion
---
>   Congestion([timeout]): This application will indicate the congenstion