That Wiki link is very North American, I remember in the late 80's configuring customer telephone switches (large key systems rather than PABXs) imported from Canada like the BT Septara and they use to refer to the incoming lines as 'Central Office' (CO) within their configuration, although not a term used here in the UK.

Edit: No comment from me regarding the earth wire

Edited by deleted (Thu 12-Nov-20 16:16:37)

In reply to a post by RobertoS:

Nobody on this forum knows what has been done inside or outside that connector box since it was (presumably) properly wired up some time ago. Many seem to be assuming that whatever disconnecting has been done has been carried out by a BT engineer, or a contractor, or a house wiring electrician, or a DIY job, and done correctly.

Of course none of those ever does a slapdash job. (In case of doubt about that list, I have never known a GPO/BT/Openreach engineer be slapdash. It's just a list of the possible disconnectors. I would be amazed if a "BT" one was involved in leaving the assembly looking like that).

Just to let you know: I have an external BT66 junction box that still has a single copper earth wire leading from it to ground, it is not connected to the terminals within the box but from a casual external view one might think it is. Several years ago the internal NTE5 was relocated by a BT/OR engineer and wired to that junction box but that earth wire was not fully removed.

Actually the drop wire connections within the BT66 are done through a screw block terminal and one day i need to get them replaced with gel crimps

Edited by 4M2 (Thu 12-Nov-20 17:09:58)

Had one as a child, shared with lady up the road. Each had its own number so only rang for the number called.

Just looked it up, ring current was over A leg and earth for one and B leg and earth for the other. Voice over A & B which is why you could hear the other party when they were using the line.

As a child of the 70s, I remember us having a party line. We had the very modern (for the time) Trimphone, rather than the more traditional GPO dial phone of the time.

At the base of the phone at the front there was a long "switch bar" which needed to be pressed to get a dial tone. I never understood why - but I do now!

I remember my parents often commenting about "someone else on the line" and recall them mentioning the party line.

Our property was on the boundary for the Cosham and Fareham exchanges in Hampshire. Our party line was on the Cosham exchange. I guess being a new estate and on the exchange fringe meant there weren't enough E side pairs left.

By the late 70s, I remember every house in the estate was switched over to the Fareham exchange - I suppose a new cabinet and expansion of E side cables took place and we got a new number. The Trimphone was replaced - and this time it was a variant without the switch...

My current late 1970s property has the later style GPO junction box, with a new cable from there to a modern NTE. The junction box still has an earth wire on an unused terminal, so I presume this property used to have a party line as well.

I've got no idea if this house had anything like that or not. The house has been in the family since my grandparents had it built in the 60s. I was born in 1980 so it's possible

The younger people on the forum maybe do not know the 'Earth' wire did not have any insulation like nowadays, that in the photo looks like 3/.029", if I remember correctly you also had 7/.029" = 7 strands of 0.029" bare tin coated copper wires.

Your mention of 3/.029 caught my eye.

Back in the early 1970s, our telephone number was the Name of the Exchange 3029 a few years later 54 was added and it became 543029. However in between that I was thinking one day, I know that number and thought that I knew someone else with a number ending 3029. Then it dawned on me, 3 strands of 0.029 inch diameter wire as used relatively recently for lighting circuits, now 1mm ^2

Annoyingly after our house was built we had to wait months for the Post Office as it was to connect the 30 or so house to the local exchange. All but one house had a telephone line. Then a few years later the house next door to ours, the one without a phone, wanted one. So the Post Office decided that ours and the house across the road would become party lines - the house which then had the new connection got an exclusive live!

We had two phones, permanently connected as they were then with the bells in series and utilising the ring capacitor in one of the phones. Since there was a concrete path all around our house, they could not fit an earth rod, so instead connected one of the 4 cores to the main earth terminal of our electricity supply. Not a neat job. The Engineer simply opened up the insulation of the 4-core cable and connected a wire to it and wrapped it with insulation tape. The other end going into the earth terminal.

It proved annoying; especially when I was away at sea and after waiting an hour or so for a telephone call home to find that the phone number was engaged when it wasn't. The way out of that then being the Post Office Radio Station at Portishead to get the local operator to break in on the call taking place and advise of an incoming call.

Those were the days?

Cheers!

Dunning-Kruger in full effect I think.
Those who work with this stuff, (and you've had several people with a combined professional experience probably in excess of double your lifetime) understand what it is, what it did when in use, how it did it and that it is no longer in use.

If it is connected to an otherwise unused terminal, what did it ever do?

I don't know how many times you need this explaining?
The earth was connected to a switch inside the telephone used to signal the exchange. The shared service telephone has been removed, ergo the switch has been removed too, so the earth is no longer connected to anything.

In reply to a post by panda:

Dunning-Kruger in full effect I think.
Those who work with this stuff, (and you've had several people with a combined professional experience probably in excess of double your lifetime) understand what it is, what it did when in use, how it did it and that it is no longer in use.

If it is connected to an otherwise unused terminal, what did it ever do?

I don't know how many times you need this explaining?
The earth was connected to a switch inside the telephone used to signal the exchange. The shared service telephone has been removed, ergo the switch has been removed too, so the earth is no longer connected to anything.

If you want a counter-example, my drop wire untiil very recently (when Openreach replaced my 18SWG flat twin drop wire for a compliant FTTP connection wiith associated copper) went into a GPO (sic) junction box with an earth wire which was both connected and not connected to the two signal wires by spark gaps. I was sad to see it bypassed!

In reply to a post by rogerh:

If you want a counter-example, my drop wire untiil very recently (when Openreach replaced my 18SWG flat twin drop wire for a compliant FTTP connection wiith associated copper) went into a GPO (sic) junction box with an earth wire which was both connected and not connected to the two signal wires by spark gaps. I was sad to see it bypassed!

Different use of earth in your scenario. Yours was for lightning protection, rather than a shared service. The terminal block in your case would have been far deeper to accommodate the surge protectors, instead of the simple block linked from the OP.
As an aside, lightning protection was discontinued as it was mostly ineffectual. It could help a little with induced surges, but not with strikes. A lightning bolt will traverse thousands of feet through air, so a minimal spark gap was pointless.