[Asterisk-Users] hangup detection

[Steven Critchfield]

On Fri, 2004-01-02 at 13:02, Sean Adams wrote:
> >
> > Are the tones increasing in pitch?
> 
> No, the beeps are the same pitch - sounds like it was deliberately  
> designed to be a loud and awful sounding as possible through an  
> off-hook phone, to get your attention to go hang it up. My ears tell me  
> it's roughly 250ms on, 250ms off and so on.

Okay.

> Taking my first peek at the code now...

Always a good thing.

> > BTW, which CAC channel bank did you buy? The ADIT 600 should do
> > disconnect supervision, and I thought the AB1 did too.
> 
> It's the AB1 with 8 fxo, 16xfs. Here's the page I was talking about:
> 
> http://www.voip-info.org/wiki-Asterisk+hardware
> 
> Also, others have reported this problem but I can't find a resolution:
> 
> http://www.mail-archive.com/asterisk-users@lists.digium.com/msg18626.html
> 
> > Are you also sure
> > you have that on your line so as to be detected? Your other option  
> > might
> > be to switch to groundstart lines which detect hangup much easier. May
> > be difficult to get unless you are a business though.
> 
> I just have regular business lines without any special provisioning. I  
> don't understand why a $20 answering machine can do this but an  
> expensive channel bank can't. :(

The difference is acceptable failure. If your $20 answering machine
fails by hanging up early, they only one really annoyed is the person
leaving a message and they will think they hit a record length limit
unless it was pretty short. If you are placing a call though the machine
and it thought the other side hung up and so it disconnected your
conversation, you would consider that unacceptable.

The other part is that disconnect supervision is something that
basically breaks the loop long enough, or reverse polarity for a moment
to let the other side disconnect. Think about how a relay would work,
reverse polarity or disconnect battery and it will disconnect the
points. Now days, that type of technology is rarely used, and therefore
not implemented unless asked for. 

It is highly probably that you don't have disconnect supervision on your
phone line. You should be able to hook up your test equipment and see
it. I think it has been discussed here before about using a phone that
takes power from the line to light up, if it blinks when the other side
hangs up, you have disconnect supervision. Otherwise, it will always be
a problem detecting hangup without waiting for those tones and matching
on them. 
-- 
Steven Critchfield  <critch at basesys.com>