Busy detection on zap channels

Hi… i have a TDM400P with 1 FXS port and 1 FXO ports but if the line 1 is busy, and i call form my ip phone using the same line, it’s like if the line are aviable because in the asterisk console i get
Called Zap…etc
Answered…etc

How i configure my dialplan to check if the line is busy or not before start calling, and if its busy, playback a message (Sorry-line-busy) if not, just call.

Thanks.
kiss :stuck_out_tongue:

[quote]If the call is unsuccessful (because either the channel
is busy or the number can’t be dialed for some reason), the Congestion() application
is called, which plays a “fast busy signalâ€