Problems receiving calls via PSTN gradually getting worse

[jmgVOIP]

I am based in the UK.

I have been using an OBI202 fitted with an OBiLine successfully for a few years. Recently I have been experiencing problems receiving calls on the PSTN line, getting gradually worse over the last couple of days and today I cannot receive any calls at all (I am using my cellphone to test).  I have not changed anything at all. I have noticed the LED on the Line port sometimes flickers for 2-3 seconds when I make the call and then stops. However other times it does not even flicker. I have also monitored the line and noticed the voltage going to around -65 as I make the call with the cellphone but it is noisy,  swinging to around -120 and sometimes goes positive to around +25v. Another observation is that sometimes it shows ringing on the status for 2-3 seconds then it turns on-hook and stays, probably in unison with the flickering of the Line described above.

I thought it might be the ObiLine or the OBI202 itself, so I swapped it for an OBI110 (my previous ATA!). Interestingly, it shows exactly the same behaviour - can make in/out calls via SP and out calls via PSTN but cannot recive calls via the PSTN line!!!

Could it be a problem with the phone line? Any ideas what to test next?

I appreciate any suggestion as I have run out of ideas!

[drgeoff]

You don't appear to have done the obvious test!

Plug your phone directly into the PSTN line and call it from your mobile phone.

[jmgVOIP]

Hello drgeoff, I forgot to say but yes I connected the phone directly and works fine. It is the OBI not able to detect the incoming call ringing. As I said, it sometimes works and sometimes shows "ringing" in the status page for 2-3 seconds and then return to on-hook. But most of the time now the OBI does not detect the incoming call - the status stays on-hook no matter how long I keep ringing.

[gsmlnx]

Have you performed the quiet line test?

This involves plugging in a corded phone to the master socket on the main phone socket.

Look at the instructions here from a UK telecoms company, it is the same for all UK land line customers irrespective of supplier AFAIAA.

https://support.zen.co.uk/kb/Knowledgebase/Performing-a-Quiet-Line-Test

[drgeoff]

Hello drgeoff, I forgot to say but yes I connected the phone directly and works fine. It is the OBI not able to detect the incoming call ringing. As I said, it sometimes works and sometimes shows "ringing" in the status page for 2-3 seconds and then return to on-hook. But most of the time now the OBI does not detect the incoming call - the status stays on-hook no matter how long I keep ringing.

That you experience the same with the 202 plus OBiline and the 110 suggests that neither of them is the culprit. Can you swap out the cables and any US to UK adsptors you are using?

One test that might give clues. If you have had the 110 for a few years it may be the hardware version that has a relay between the LINE and PHONE jacks.  It joins the two when the 110 is unpowered. Connect up using the 110 but do not plug in the PSU. Lift the handset and if you hear dial tone you have the relay version. If so, call from your mobile.  What happens.

Another test you can do is to connect the PHONE jack output of one OBi to the LINE input jack of the 110 or OBiLINE. The PHONE jack acts just like the PSTN line. You should be able to receive a SIP call to to the first device through a phone connected to the second one. (110 should be powered up.)

[jmgVOIP]

Thanks drgeoff/gsmlnx for your suggestions which I will be trying over the next couple of days. I will let you know of my findings when I conclude the tests.

[jmgVOIP]

I could not carry out a quiet line test as I don't subscribe to BT. I have carried out the first test suggested by drgeoff. First of all it is an old OBI110 and yes it has a relay which can be heard when powered on/off. If I connect a phone and power off the OBI I can make calls in with my mobile reliably. As soon as a power on the OBI I get the symptons outlined previously i.e. sometimes the line LED flickers for a couple of seconds and then stays on, but most of the time the LED stays on as a rereatedly dial i with my mobile. It seems like the OBI has difficulties detecting the signal in the same way as when loading the master sockets with various extensions and going over the REN safety value some phones will ring and some will not, presumably depending on the sensitivity/REM value of the phone.

I will try the second test later as I need to understand what drgeoff means and tryig to show. I have not my head around the connection scheme suggested.

[ianobi]

It seems like the OBI has difficulties detecting the signal in the same way as when loading the master sockets with various extensions and going over the REN safety value some phones will ring and some will not, presumably depending on the sensitivity/REM value of the phone.

That would seem to suggest that the incoming ringing voltage supplied by the PSTN line has changed - odd but not impossible. As a test you could try reducing these values:

Physical Interfaces > LINE Port > Ring Detection > RingThreshold
Physical Interfaces > LINE Port > Ring Detection > RingValidationTime

I would carry on using the OBi110 for testing, at least until you have an answer.

[drgeoff]

.. I need to understand what drgeoff means and tryig to show. I have not my head around the connection scheme suggested.

The second test is to have a different source of ringing instead of your PSTN line.  The PHONE jack of an OBi supplies DC voltage and ringing voltage to a phone in a very similar manner to how a PSTN line does it.  So the idea is to use the the PHONE jack of one OBi (say the 202) to substitute the PSTN line.  Connect a PHONE jack (the one you usually have the phone plugged in to) of the 202 to the LINE jack of the 110.  Make a call to the number that terminates on a SIP service on the 202.  That will send ringing voltage from the 202 to the 110.  If the 110 and the phone plugged into the 110's PHONE jack detect that reliably, then we would focus on why the PSTN ringing voltage seems insufficient.

It is a quite possible that you have a line fault, external to your property or internal which produces a low resistance between the two legs when ringing voltage is applied by the exchange.  (Dampness, vegetation, verdigris etc.) That could reduce the ringing voltage below the OBi's threshold but still be enough to ring your phone when connected directly to the line.  Indeed it is probably worth reducing the values suggested by ianobi as a quick and easy experiment before doing anything else.

[jmgVOIP]

Some progress, I think. I carried out the tests suggested by drgeoff and in both cases the OBIs behave as they should. It therefore seems very likely that the fault lies with the PSTN line as suggested by drgeoff and ianobi. Unfortunately changing the ringing parameters was unsuccessful. I am now left with the unenviable task to ask my phone/broadband provider (TalkTalk) to check the line. I know exactly what they are going to say; "we only give support for equipment that we have provided. The point is that the broadband works and the phone works if connected directly, so it is going to be fun trying to convince them.

In the meantime thanks a lot for the help to get me where I am considering that a posted the topic only a few hours ago. I'll let you know the outcome.

Enjoy the end of the year!

 

[SteveInWA]

What are the regulations in the UK with regard to point of demarcation and what the telco has to support in cases like this? 

Here in the US, the telco would be required to provide correctly-functioning service at their point of demarcation into the premises, with no Customer Provided Equipment (CPE).  So, that would mean that the three possible voltages on the line be within specification:  the on-hook ~48VDC, the off-hook ~12VDC, and the ring voltage (varies depending on load and loop length, etc, but in the ~70-100VAC range).  The telco should at least test and confirm that, with no customer-provided equipment attached to the line.  They should be able to detect an intermittent short or high-impedance condition.

[drgeoff]

The similarity between what the regulations say and what Talk-Talk do is often difficult to recognise!