asterisk users - Apr 2008 - Time out to disconnec: IAX trunk, SIP Trunk, Zaptel Channel

Hi All;

I would like to know if any one can helps or have idea
on how to disconnect the call in case no media (all
parties hanged up, but the channel still open) for the
following cases:

1) If we have IAX trunk, then how to disconnect the
call automatically after specific time (time out
media) if all parties closed and no more media packets
is moving between the endpoints?

2) If we have SIP trunk, and same above senaio?

3) In case the call came for the Zaptel channel (FXO)
and the source disconnect the call and the disconnect
signal was not detected as the telecom service
provider does not send it and asterisk did not detect
it, so: how to hangup zaptel automatically after a
specific timeout as no more media is going through?

Any help?
Regards
Bilal

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