[asterisk-users] How to avoid automatic answer with callwaiting=yes on fxs channels?

[Niccolò Belli]

I will make an example:
A is an fxs phone with callwaiting=yes in chan_dahdi.conf

X calls A. A answers.
Y calls A. A hears the call waiting tone.

Now if A hangs up before X, then A rings again (which is what I want).
BUT if X hangs up first, then A automatically answers Y without even 
ringing. Is there a way to avoid it? If X hangs up first I want A to 
hear the busy tone until it hangs up too. Then I want A to ring again. 
Otherwise if both A and X hang up at the same time there is no way to 
know what happened.

Thanks,
Niccolò
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