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Author Topic: OBI110 Disconnect Detection not working on UK PSTN  (Read 39986 times)
paulm
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Posts: 5


« on: November 21, 2015, 03:17:33 pm »

Hi All - I've recently purchased an OBI110. I've loaded the UK Configuration XML file (from here: http://www.obitalk.com/forum/index.php?topic=8434.0) and most things seem to be working fine.  Certainly, I can make and receive calls via the landline without any problem.  However, I am having problems with the disconnect detection.

If a call is connected and the far end disconnects, the Obi110 continues to stay on the line (for at least a few minutes - complete with various warning noises and periods of silence provided by the Telco).  The behaviour I'm expecting is that the Obi110 detects the disconnect and puts the Line Port on-hook immediately.

So, two questions really.  First, is my expectation about the Obi110 hanging-up immediately correct - is this what the device should be doing?  Second, are there other settings that need to change to get this working?

Have already seen and tried advice in https://www.obitalk.com/forum/index.php?topic=9060.0 and https://www.obitalk.com/forum/index.php?topic=679.msg5575#msg5575.  Have tried, at Obihai helpdesk suggestion, all the various ACImpedence settings.

Any help greatly appreciated.

Thanks, Paul

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Second,

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ianobi
Hero Member & Beta Tester
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Posts: 1828


« Reply #1 on: November 22, 2015, 01:23:56 am »

Quote
First, is my expectation about the Obi110 hanging-up immediately correct - is this what the device should be doing?

Yes! Within 2 to 3 seconds.


Quote
Second, are there other settings that need to change to get this working?

The only relevant settings are those in Physical Interfaces -> LINE Port -> PSTN Disconnect Detection.

Here's the relevant quote from British Telecom info:
British Telecom CPC duration may be between 90ms and 130ms.
British Telecom Disconnection Tone is a minimum of 3 seconds 400Hz at -30dBm.

The settings that work for me are:
DetectCPC - enable
CPCTimeThreshold - 100  (you could try as low as 90)
DetectDisconnectTone - enable
DisconnectTonePattern - 400-30;3 (you could try 400-30;2)

All other PSTN Disconnect Detection settings disabled.

Are you using a BT line? I used to use Virgin Media and I know they inherited a real mix of exchanges from the various original cable companies. Many of these used different methods for PSTN disconnection detection.

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paulm
Newbie
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Posts: 5


« Reply #2 on: November 22, 2015, 02:08:57 am »

Quote
Quote
First, is my expectation about the Obi110 hanging-up immediately correct - is this what the device should be doing?

Yes! Within 2 to 3 seconds.

Thanks for the confirmation.  That's immediate enough for my purposes and certainly not the behaviour I'm getting.

Quote
The only relevant settings are those in Physical Interfaces -> LINE Port -> PSTN Disconnect Detection.
...
Are you using a BT line? ...

I've tried your settings without any success. They're pretty close if not identical to what is in the UK XML file so no surprise there.  Yes. I'm using a BT line.  I am a fair distance from the exchange (5 miles or so) and this causes some issues with my broadband ... is it likely that this would cause problems with the OBI110 too?

Thanks for your help

Paul
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ianobi
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Posts: 1828


« Reply #3 on: November 22, 2015, 03:06:27 am »

Disable all PSTN disconnection options. Make a call into your PSTN line (from mobile maybe). Establish call, then clear down mobile. You should now hear "NU" tone after maybe a short break. If so listen to how long it lasts. The OBi110 will not disconnect as you have removed all of the disconnect functions, but at least you will prove that "NU" is there.

It's hard to test for CPC unless you have an oscilloscope handy! CPC is simply a short removal of voltage from the line. The capacitance of your five mile line may be making the CPC shorter or longer - hard to say.

Now try both disconnect methods one at a time. Try settings outside the limits. Maybe a CPC of 80 or try much longer settings. Less than 80 risks false disconnections. Disconnect tone may be being attenuated by your long line so maybe try 400-35;2 or 400-40;2 to detect a fainter signal. Again going too low may lead to false disconnections.
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paulm
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Posts: 5


« Reply #4 on: November 22, 2015, 04:43:25 am »

Quote
...at least you will prove that "NU" is there.

It's there alright.  It goes on for about 15 seconds.  According to the tuner app on my phone it is pitched at 392Hz.

Quote
It's hard to test for CPC unless you have an oscilloscope handy!

I do have one handy as it happens! But it's not a fancy storage scope which I think I'd need to see this one off event.

Quote
Now try both disconnect methods one at a time. Try settings outside the limits. Maybe a CPC of 80 or try much longer settings. Less than 80 risks false disconnections. Disconnect tone may be being attenuated by your long line so maybe try 400-35;2 or 400-40;2 to detect a fainter signal. Again going too low may lead to false disconnections.

Still no joy.  I hadn't thought of changing the Disconnect Tone attenuation before. I've tried down to 400-62;2 (and 392-62;2) on the Disconnect Tone and down to 10 on the CPC detection threshold and I cannot even get a false disconnection!  I think this item might have to go back to Amazon for replacement.

Thanks for your help
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paulm
Newbie
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Posts: 5


« Reply #5 on: November 26, 2015, 10:03:04 am »

The replacement OBi110 arrived today. Have loaded it up with the UK XML file and it is detecting disconnects.  CPC detection still isn't working, but it is detecting the 400Hz tone and going on-hook after a few seconds.  It is maybe a bit longer delay than I would like, but I shall probably live with it.

Now have to arrange to send the old one back for a refund.

Thanks to ianobi for the helpful responses!
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paulm
Newbie
*
Posts: 5


« Reply #6 on: January 27, 2016, 10:03:31 am »

Sorry to bring up an old subject.  I thought it was fixed...

The replacement OBi110 arrived today. Have loaded it up with the UK XML file and it is detecting disconnects.  CPC detection still isn't working, but it is detecting the 400Hz tone and going on-hook after a few seconds.  It is maybe a bit longer delay than I would like, but I shall probably live with it.

But after spending a little while (well, a couple of months) of slowly getting pbx and ip phone extensions configured and working I tried to get voicemail running today and found the problem has returned.  Unfortunately I have no idea at what point the Obi110 stopped detecting disconnects as I wasn't making a point of testing this along the way.

I've done a factory reset and re-loaded the UK XML configuration file...with the same settings that worked when I took delivery of this particular device...but this has not cured the problem.  The disconnect tone is still there when the caller hangs up, and I've tried some different changes to the disconnect tone pattern setting on the Obi110 as suggested previously in this thread, but still the Obi110 now consistently fails to detect the disconnect.

Any ideas on how to get disconnect detection back?  Alternatively, is there some workaround that I could implement in the PBX?  I'm using Raspbx (FreePBX and Asterisk running on a Raspberry Pi).

Any help greatly appreciated.

Thanks, Paul
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ianobi
Hero Member & Beta Tester
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Posts: 1828


« Reply #7 on: January 28, 2016, 06:13:39 am »

It seems unlikely that two OBi110s have the same problem. In OBi terms it is now quite an old and proven reliable device. Time to eliminate other factors if possible. If it's not an OBi problem, then it must be some other problem in your setup or a problem with your BT line.

Where your BT line enters your home (the NTTP socket) you can disconnect all of your internal wiring from the external BT line. Try connecting your OBi110 at this point to the BT line and try CPC and disconnect tone functions one at a time from there.

If they are feeling helpful, BT can give you a whopping 800ms CPC. See this article:

http://www.stocksy.co.uk/articles/Networks/how_to_get_disconnect_supervision_on_your_bt_telephone_line/

If they agree to do this, then set your OBi110 CPC to something below 800ms - say 600ms.
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