[asterisk-users] Installed TDM02B - Problem when other end hangs up

[Stephen Bosch]

Stephen Bosch wrote:
> Lee Jenkins wrote:
>>> Well, not really -- when the extension hangs up, Asterisk knows the
>>> channel has been abandoned and clears it.
>>>
>>> When the remote party hangs up first, the card doesn't tell Asterisk
>>> that the channel is clear (because it doesn't know the caller has hung
>>> up), so Asterisk has no idea and presumes it is unavailable.
>>>
>> Interesting.  But if that was the case, wouldn't restarting asterisk
>> (#CLI restart now) clear the problem?  Because on my system, it does not
>> clear the problem, only a complete restart of the server seems to work.
>>  Well that and trying again some considerable time later which may or
>> may not work then.
> 
> That's because I assumed (based on what you said in previous posts) that
> the card thought the line was clear, but if your experience is anything
> like mine, the card leaves the channel open because it doesn't detect
> the disconnect signal from the CO.
> 
> If the card still thinks the line is in use too, it will refuse access
> to the channel. That's why restarting Asterisk doesn't help.
> 
> I'm getting a test dongle and a multimeter to see if I can observe a
> disconnect supervision signal on one of my lines.
> 
> I'll let you know what I find. It will take me a few minutes.

Okay. Here's what I can tell you.

Scenario:

On hook state: line voltage is 52 VDC.
Phone A calls Phone B
Off hook state: line voltage is 7.5 VDC.
Phone B answers
Phone A and Phone B yak
Phone B hangs up, but Phone A stays on the line
After ~65 seconds (give or take a few milliseconds), the CO drops the
voltage to 1.5 volts (from 7.5) for roughly half a second, then the
voltage returns to 7.5. No polarity reversal (unless the reversal is so
quick that my digital multimeter doesn't have time to display it, which
is also a possibility; what I suppose really need is an analog meter...
how ironic).

So, my telco is doing some kind of disconnect signalling. The question
is whether the TDM card can detect it.

Either way, 65 seconds is a bloody eternity in the phone world. That's
65 seconds during which the line can't be used...

Am I the only one who thinks that's insane? I'd be interested in some
feedback from other users; how long does it normally take to get a
disconnect signal in your area?

The repair guy I talked to said that it was pretty much an impossibility
that I would ever get them to reduce the delay and to forget about it
immediately.

I'm going to do some testing later today to see if that 65 second delay
is consistent or totally random.

-Stephen-