Thanks Jim, nicely put!
There is a disconnect signal available from some carriers called "Kwel Start"
(spelling may be wrong)
This reverses Tip and Ring polarity for a instant on disconnect. Some FXO cards
can be set to use this to
signal a hang-up. Apparently, the way to check if this is available is to
optain an old "Princess" phone
with a neon lamp , when the far end disconnects the neon lamp flashes,
indicating a line reversal (Tip and Ring).
Note: Before analog lines were in common use, several references to "cutting
the string" were used :)
TTFN ---H
=================================
Henry L.Coleman [www.VoIP-PBX.ca]
Tel: 647-723-5160 Ext.203
=================================
{ Jim Van Meggelen}
> Waaaay back in the early 90s when voicemail was not yet ubiquitous,
> far-end disconnect supervision for loop start analog lines was something
> that didn't really exist. They were lines, not trunks (the CRTC acually
> tariffed PBXs and Key Systems differently, as well as the kind of
> circuits you could connect to them). It was never a problem before
> voicemail, because as long as your phone system hung up the line (which
> is what would happen when you hung up your phone), the circuit went
> on-hook at your end, and the call was terminated correctly.
>
> If you wanted far-end disconnect supervision, you had to get a
> ground-start trunk. These were analog circuits that didn't use a loop to
> request dial tone, but instead used a ground (we had an extra wire in
> our butt sets so we could ground the line to the frame to get dial tone
> when we were testing.
>
> As voicemail systems became more common, far-end disconnect supervision
> on small key systems became a problem. Lines would appear to be hung,
> but in reality what was happening was that the voicemail simply didn't
> have the smarts to realize the far end was disconnected, and so it
> wouldn't hang up the call.
>
> The solution was a hack. Carriers began to implement disconnect schemes
> on analogue lines. They would send a signal of some sort to indicate to
> the system that the far end had disconnected. This was never perfect,
> and still isn't (although it's pretty darn good).
>
> So the problem is not only related to Asterisk. Any voicemail system on
> a loop-start analog system has to take into account the facts that a)
> the disconnect will not come immediately, and b) sometimes it will not
> com at all.
>
> I don't think that there will ever be a way to solve this problem 100%
> of the time, but you can get close.
>
> The first thing to set correctly is the silence threshold. Three seconds
> is too short, ten seconds too long. What seems to work is about 5 seconds.
>
> maxsilence=5
>
> The next thing to figure out is if we end a recording after 5 seconds of
> silence, we will set our minimum message length to 6, which is one
> second higher than the silence. This will ensure that any message that
> is a result of the caller hanging up and not leaving a message, will
> always be 5 seconds (because that's the silence threshold), and thus
> will not be a valid message (because it is not the minimum of 6 seconds).
>
> minmessage=6
>
> You will have to tell your clients that any messages less than 6 seconds
> may be treated as a hangup by the system. They might not like it, but
> I've never seen anybody unable to get over it.
>
> If you really want to play it safe, you should put something in your
> dialplan to set the absolute maximum length of a call. That could even
> be a few hours if your clients talk on the phone for a while, but at
> least that way the call will always disconnect eventually.
>
> The simple fact is, if you want reliable, fast, far-end disconnect
> supervision, you cannot use analogue circuits.
>
> Jim
>
>
>
>
> Nabeel Jafferali wrote:
>> Thanks for the info.
>>
>> Yes, I do get that, meaning the call does hang up 10-11 seconds after the
>> remote party hangs up. This
>> also means Asterisk voicemail gives me 10 second blank messages if the call
>> had ended up in voicemail.
>>
>> Any way around that?
>>
>> --
>> Nabeel Jafferali
>> X2 Networks
>>
>>
>> -----Original Message-----
>> From: Jim Van Meggelen [mailto:[email protected]]
>> Sent: February-09-09 5:53 PM
>> To: Nabeel Jafferali
>> Cc: [email protected]
>> Subject: Re: [on-asterisk] Audiocodes - Disconnect Supervision
>>
>> You have to wait for the far-end disconnect from the carrier. If you
>> have a butt set you can monitor the line and listen for it. I have found
>> it usually takes about 11 seconds to get the signal.
>>
>> Nabeel Jafferali wrote:
>>
>>> I have an Audiocodes MP-118FXO in production. When a call is made and the
>>> remote party hangs up, the
>>> Audiocodes hangs up the call immediately. But if a call is received and the
>>> remote party hangs up, the
>>> Audiocodes does not hang up immediately.
>>>
>>> Anyone experienced this issue with Audiocodes or any other gateway in
>>> general? Any tips?
>>>
>>> --
>>> Nabeel Jafferali
>>> X2 Networks
>>>
>>>
>>>
>>>
>>
>>
>>
>
>
> --
>
> --
> Jim Van Meggelen
> [email protected]
> http://www.oreillynet.com/pub/au/2177
>
> "A child is the ultimate startup, and I have three.
> This makes me rich."
> Guy Kawasaki
> --
>
>
>
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