[Asterisk-Users] Zap channels not disconnecting after PSTN line hangs up (getting empty voicemails)

[Mike Garey]

When someone calls into our asterisk server over a PSTN line, dials an
extension and then hangs up, the SIP phone related to the given
extension will ring about 4 or 5 times before asterisk shows that the
channel has been hung up in the console.  This isn't such a big deal
on its own, but what's happening now is that if a user calls in from a
PSTN line, gets voicemail on the extension, and hangs up before the
voicemail starts to record, an empty message will still be recorded
and sent to the user.

I've tried setting "minmessage=3" in voicemail.conf, but that only
seems to work when calling from SIP phone to SIP phone - for calls
through the PSTN, it makes no difference (since it seems the Zap
channel isn't disconnecting immediately).

I'm also curious about the maxsilence setting in voicemail.conf, it says:

"Maxsilence defines how long Asterisk will wait for a contiguous
period of silence before terminating an incoming call to voice mail.
The default value is 0, which means the silence detector is disabled
and the wait time is infinite. Maxsilence takes a value of zero or a
positive integer value which is the number of seconds of silence to
wait before disconnecting."

does that mean that once a call goes to voicemail, asterisk will wait
maxsilence seconds before disconnecting the call, even if the user is
still connected? I guess this is for handling the case where the
dialing in user is still connected, but hasn't actually said anything,
ie, they may have had to rush away from the phone for some emergency
without hanging it up first, so rather than have asterisk record
everything, it disconnects after maxsilence seconds have elapsed with
no sound..  If this is the behaviour, then it looks like maxsilence
has nothing to do with preventing a dropped call from being recorded
in the first place, since it seems that the maxsilence behaviour is
only applicable after voicemail has already picked up.

So if anyone has any other suggestions, please let me know, since I'm
getting a lot of complaints from users about empty voicemails, and
would like to fix this as soon as possible.  Thanks in advance,

Mike