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Author Topic: Retirement of PSTN - line diagnostics?  (Read 440 times)

moojuice

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Retirement of PSTN - line diagnostics?
« on: May 29, 2021, 04:34:20 PM »

So BT / Openreach plan to retire PSTN by 2025, going Digital Voice. When this happens, how would one diagnose an ADSL / VDSL line fault as a consumer? Currently the first go-to is to plug a known good hardwired analogue phone into the test socket and dial 17070 and listen out for crackles and pops on the quiet line test. It would be good to know, if an analogue phone is still connected post switchover, that there's some sort of automated tester still on the line based in the exchange, even if it doesnt connect allow you to call any other number.

What do those on migrated Digital Voice services get today if they plug an anlogue phone into the master socket? An automated message? Is 17070 still live post switch over?
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dslexpert

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Re: Retirement of PSTN - line diagnostics?
« Reply #1 on: June 09, 2021, 05:44:40 PM »


170xx won't work any more but I'm not sure it's a particularly useful test method; you can only hear issues in the voice band (not used by DSL); the same impairment may also be affecting the DSL band, but DSL is adaptive and will avoid impaired bins (carrier frequencies) when setting the realtime line profile.  The diagnostics in your modem/router are more useful in seeing line quality - errors, bins in use, CRC issues etc. especially if you take a baseline snapshot during the good times (see attached image).


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j0hn

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Re: Retirement of PSTN - line diagnostics?
« Reply #2 on: June 09, 2021, 05:57:03 PM »

There's no dial tone on SOGEA (Digital Voice).
17070 no longer works.
The ISP can still run line tests though.

A noisy/crackly line only helps diagnose some xDSL faults.
17070 was designed to detect issues with the voice service. With calls moving to IP it no longer serves its purpose.
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Alex Atkin UK

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Re: Retirement of PSTN - line diagnostics?
« Reply #3 on: June 09, 2021, 06:04:31 PM »

I'm more curious if they can expand the band plans of DSL to use voice tones?
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j0hn

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Re: Retirement of PSTN - line diagnostics?
« Reply #4 on: June 09, 2021, 06:48:42 PM »

I'm more curious if they can expand the band plans of DSL to use voice tones?

It could be more trouble than it's worth.
It would only be a tiny increase in the U0 band.
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dslexpert

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Re: Retirement of PSTN - line diagnostics?
« Reply #5 on: June 09, 2021, 06:52:39 PM »

I'm more curious if they can expand the band plans of DSL to use voice tones?

No; the DSL specs. exclude carriers below 4Khz. and as and 'older' technology (relatively) I doubt anyone has much interest in amending the ITU-T specs for what is a tiny bit of extra bandwidth.
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Alex Atkin UK

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Re: Retirement of PSTN - line diagnostics?
« Reply #6 on: June 09, 2021, 08:17:40 PM »

No; the DSL specs. exclude carriers below 4Khz. and as and 'older' technology (relatively) I doubt anyone has much interest in amending the ITU-T specs for what is a tiny bit of extra bandwidth.

That kinda surprises me, you'd think PSTN switch-off would have been considered.  I guess they never figured it would happen BEFORE FTTP became standard.
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jelv

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Re: Retirement of PSTN - line diagnostics?
« Reply #7 on: June 09, 2021, 10:23:54 PM »

170xx won't work any more but I'm not sure it's a particularly useful test method; you can only hear issues in the voice band (not used by DSL); the same impairment may also be affecting the DSL band, but DSL is adaptive and will avoid impaired bins (carrier frequencies) when setting the realtime line profile.  The diagnostics in your modem/router are more useful in seeing line quality - errors, bins in use, CRC issues etc. especially if you take a baseline snapshot during the good times (see attached image).

As a very easy first check for someone with minimal technical ability I think it's useful. If there's significant problems with the voice line, there will be issues with DSL. I can't recall ever seeing a report of someone having voice issues and the DSL being fine.
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craigv

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Re: Retirement of PSTN - line diagnostics?
« Reply #8 on: June 09, 2021, 10:28:41 PM »

As a very easy first check for someone with minimal technical ability I think it's useful. If there's significant problems with the voice line, there will be issues with DSL. I can't recall ever seeing a report of someone having voice issues and the DSL being fine.

I agree, for sure. When my line had serious issues and the VDSL would constantly drop or be unstable, it was the terribly crackly quiet line tests that I collected as proof which that convinced the engineers that there genuinely was an issue, even if it still took 6 visits, they at least knew I wasn't just crazy!

That being said, I'm not sure anybody without technical knowhow is calling up and doing quiet line tests. :D
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hopkins35

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Re: Retirement of PSTN - line diagnostics?
« Reply #9 on: June 12, 2021, 08:31:45 AM »

Andrews & Arnold have re-instated their own version of 17070 on their broadband only lines which features Adrian Kennard's voice, he's the company director for those who don't know, saying "quiet line test" which is quite amusing and useful to still have access to
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