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Old 19th Aug 2014, 7:11 pm   #1
recordamus
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Default 1950s/60s 'phones on BT exchange lines

I have a 706L and a 746 GPO 'phone. The 706 was modified and now has a RotaTone DTMF (pulse-to-tone) converter fitted - and everything worked tickety-boo UNTIL I had BT Infinity 2 FTTC broadband installed recently. Now, neither 'phone works: no dial-tone and no 'battery' (side-tone).
Curiously, we have a Binatone corded base with two wireless handsets which continues to work perfectly! Wonder if anyone has any ideas? I've tried everything I know.
Pete
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Old 19th Aug 2014, 7:14 pm   #2
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Default Re: 1950s/60s 'phones on BT exchange lines

That's very odd.

Try them via a good quality plug-in microfilter and report back, if you can.

N.
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Old 19th Aug 2014, 8:04 pm   #3
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Default Re: 1950s/60s 'phones on BT exchange lines

Thanks, Nick. I've tried 3 different vintage phones and removed the faceplate of the BT line socket to try the 'phones in the internal plug. Still the same. I just can't figure it out at all. Is it that the 706 is presenting too low an impedance to the line, do you think? As I said in my original posting, the modern Binatone corded phone - which, of course, is the 'phone which is normally plugged into the linebox (built-in filtering, by the way) along with the Open Reach modem which supports the BT Home Hub 4 - still works just fine. This has only happened since Open Reach fitted the new linebox, modem and hub.
P.
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Old 19th Aug 2014, 8:22 pm   #4
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Default Re: 1950s/60s 'phones on BT exchange lines

Do try a microfilter as they contain a ringing capacitor.

How are the phones wired? "Converted" in the usual way to 3-wire PTSN plug-in working?

N.
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Old 19th Aug 2014, 10:26 pm   #5
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Default Re: 1950s/60s 'phones on BT exchange lines

Polarity swapped?
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Old 19th Aug 2014, 10:45 pm   #6
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Default Re: 1950s/60s 'phones on BT exchange lines

Nick - I'll get back to you in an hour or so when I've managed to lay my hands on a micro-filter (got one somewhere!)

Biggles: I did wonder about that - but as I have said, the old 'phones did work before BT installed Infinity 2 FTTC and nothing has since been changed on them. One has had a RotaTone pulse-to-tone converter fitted and one is 'original' (no mods - still pulse dialling). The one with the RotaTone is fitted with a bridge rectifier as polarity reversal protection. AND the Binatone modern corded base has not been affected.

Thanks for taking the trouble to respond.
Pete
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Old 19th Aug 2014, 11:34 pm   #7
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Default Re: 1950s/60s 'phones on BT exchange lines

Nick - I've plugged a brand new microfilter into the BT linebox and it makes no difference to my problem. The linebox has Open Reach written along the top and a connection to the Open Reach modem below which is a conventional socket for the telephone.
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Old 20th Aug 2014, 4:57 pm   #8
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Default Re: 1950s/60s 'phones on BT exchange lines

Measure across L1 L2 when receiver is on and off hook. You should get about 50V on hook, about 7 or 8 volts off hook. Compare this with results on the new phone. Are they very different? If you are now using fibre, the exchange will not have a hard wire connection, and presumably there is some kind of interface to the fibre to provide "normal" line conditions for phone use. It may be that this can't supply enough line current to operate an old phone, but may well be compatible with new phones. Try your old phones in a normal line in another house if you can, to see if they behave normally with a hard wired connection.

Last edited by Biggles; 20th Aug 2014 at 4:59 pm. Reason: typo
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Old 20th Aug 2014, 10:15 pm   #9
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Default Re: 1950s/60s 'phones on BT exchange lines

Quote:
Originally Posted by Biggles View Post
......If you are now using fibre, the exchange will not have a hard wire connection, and presumably there is some kind of interface to the fibre to provide "normal" li.e conditions for phone use......
As far as I am aware the only difference with BT "fibre to cab" connection is the relocation of the DSLAM (Digital Subscriber Line Access Module) to the cab rather than at the exchange end, which allows faster broadband speeds to be achieved, and the copper pair from/to the exchange and customer premises should not have changed, or may now be multiplexed on to the fibre feed at the street cabinet in similar fashion to how cable operators provide their telephone voice (not broadband) services.

Quote:
Originally Posted by Biggles View Post
..........It may be that this can't supply enough line current to operate an old phone.......
Considering the above the line current should be better if anything, it does seem odd however that the phones worked fine before the broadband service was changed, especially as there is now no voice operation. Has the OP tried plugging his phones into the test socket behind the new Master socket? It's not unknown for the faceplate on the NTE5 (Master socket) to become faulty, even when new.

Regards

Andrew
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Old 20th Aug 2014, 11:45 pm   #10
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Default Re: 1950s/60s 'phones on BT exchange lines

Ok Andrew, I stand corrected on that one. I'm not that well up on the fibre side of distribution, our stuff is mainly copper to the end user. It does seem too much of a coincidence that problems started when infinity was installed.
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Old 21st Aug 2014, 7:43 pm   #11
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Default Re: 1950s/60s 'phones on BT exchange lines

I'm grateful for all your comments. Regrettably, the situation remains un-resolved. I only have the use of one arm/hand these days so getting out the Avo is no longer an option for me, I'm afraid to test the on hook/off hook line voltages. Oh, the joys of advancing years!! Will keep an eye on my original posting, just in case.
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Old 21st Aug 2014, 10:53 pm   #12
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Default Re: 1950s/60s 'phones on BT exchange lines

Ok Recordamus, that would be the sensible option if you aren't too confident with checking voltages on the line. They are of a magnitude to be classified as dangerous, particularly ringing voltage when present. Regards. Alan.

Last edited by Biggles; 21st Aug 2014 at 10:54 pm. Reason: typo
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Old 21st Aug 2014, 11:13 pm   #13
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Default Re: 1950s/60s 'phones on BT exchange lines

Thanks, Biggles. It's not that I'm not confident, though (I've been an electronics engineer all my working life!) it's just that I have very little mobility now following a bad stroke - so I am physically unable to do these things. I used to love restoring vintage radio - and telephones, for that matter - until I was incapacitated. I have got these 'phones left from my pre-stroke days and they used to work fine - until BT fitted the Open Reach modem and the Home Hub 4 - then disaster! It is so frustrating that I just can't identify why they have suddenly stopped working. I did wonder if they presented too low an impedance to the line and that the line, since the Infinity FTTC installation, is no longer capable of supplying sufficient current to operate an old vintage 'phone.
Best wishes - Pete
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Old 21st Aug 2014, 11:29 pm   #14
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Default Re: 1950s/60s 'phones on BT exchange lines

These old phones are very sensitive though. Even a very low voltage should cause an audible click in the receiver when the gravity switch is operated if some line voltage is present in the right place, and surely if the phones are loading the line too much, then your modern phones would cease to work too.

I hope someone who's able to have a poke around with a meter comes to your rescue.

Nick.
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Old 22nd Aug 2014, 5:16 pm   #15
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Default Re: 1950s/60s 'phones on BT exchange lines

Sorry for underestimating your skills Pete, sometimes it's best to err on the safe side. This problem sounds like it may be that the new equipment just seems to be incompatible with your old technology. It would definitely prove something if you could try the old phone on another line without the FTTC broadband connected. If you can't even get a dial tone or a click, it would suggest that there is not enough power being supplied to operate the old phone. As a matter of interest, can you "ring in" form a mobile phone to see if the line will ring on the old phone?
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Old 27th Aug 2014, 6:11 pm   #16
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Default Re: 1950s/60s 'phones on BT exchange lines

This has me worried, when my area switches over, I have five rotary dials. From I what I read online about the American fibre optic network, no idea if it's the same for the Uk. It carries no power, but then I'm stumped as to why your Binatone phone works.
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Old 28th Aug 2014, 3:08 pm   #17
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Default Re: 1950s/60s 'phones on BT exchange lines

Misleading advertisements aside, they don't actually install fibre optic right the way to your premises, unless you're a heavy user (for example, a business with sixty phone lines). Then, you get several Primary Rate ISDN lines down two fibres (one for Tx, one for Rx); and you have to supply your own power to the NTE2 (Network Termination Equipment, which converts from fibre to copper) and whatever device you have that plugs into the PRIs (nowadays, typically a computer implementing a PABX in software).

If you just have one or two analogue phone lines, as is usual for a hme or small business, it will be copper to the premises; but those lines may well be multiplexed onto fibre in the wiring cabinet.

At any rate, the Digium TDM410P (and cheap Chinese clones) can handle pulse dialling and isn't too fussy about timings; so you could always build your own PABX to show off your phone collection.
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