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Old 3rd Jul 2019, 10:54 am   #1
G6Tanuki
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Default A question about overhead phone-lines.

All the photos of pre-WWII street-scenes have the 'classic' telegraph-poles with multiple cross-bars and a separate insulator for each wire.

Same goes for railway-lines of a similar age - poles, cross-bars, and multiple separate wires.

When exactly did the change to insulated-pairs take place? My parents' house was built in 1958 and that had a single insulated-pair incomer but this was still attached to one of the old black tar-and-asbestos type insulators. The incoming cable - after being looped round the insulator - disappeared up inside the base of the insulator and a thinner cable then came out the same way - from memory the top of the insulator unscrewed and there was a junction-box inside to transition from the overhead-wire to the wire which led to the phones in the house.

When did this change from paired bare-wires to insulated-pair take place?

Also, in the 1970s I remember seeing multi-pair cable strung between telegraph-poles and every 7 or 8 poles there was a thin yellow-greyish wire/tube running down the pole to some sort of fitting - to me it looked more like a tube-connector than a socket. What was this for? Did they pressurise the multi-pair cables somehow to keep moisture out?
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Old 3rd Jul 2019, 7:10 pm   #2
Pellseinydd
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Default Re: A question about overhead phone-lines.

Covered 'drop-wire' a one pair cable started to appear in the 1930's - (see page 1158 in Vol 1 of Herbert & Procters 'Telephony' published in 1934) - attached at each end to eccentric pulley wheel that clamped the single pair cable.

Exact dates for the introduction would be hard to establish - only the approximate year. The eccentric pulley wheel (still seen on odd brackets on buildings) was later replaced by a 'clamp' that dropped over the spindle at each end to support the cable. Usually only a single spare from a 'ring' type distribution pole. Then in the late 1950's more types of single and two pair drop wire started to appear - usually polythene covered and held by a curly 'pigtail' clamp' and still in use today. They replaced the bare cadmium copper wires on insulators. There wasn't a junction box in the No 16 screw type insulators. But there was a three way 'drop in' block terminal (three way because of the proliferation of party lines sharing the same pair of wires at the exchange. There are still the odd pairs of bare copper wires in remote locations.

The last bare copper wires on a junction route connecting an exchange to the rest of the network went out of use in March 1995 in NW of Scotland between Diabaig and Torridon, a distance of about ten miles on a route built in the 1870's to carry a single telegraph wire to Diabaig. There was no road to Diabaig until the 1960's but the route built by the Royal Engineers for the GPO climbed up to 1600 ft as it crossed a mountain range. That steep that in places, the bottom of one pole was higher than the top of the preceding pole! The pairs for the telephone exchange were added were added in 1937 when a small magneto exchange for the two telephone lines in Diabaig opened in 1937. The open wire route was replaced by three microwave links when the exchange went digital in 1995. I have photos of the route plus a video of the little bit of telecoms history (No 36 in 'Great Pole Routes of the World' )

The 'tube connector' would have been a 'jointing sleeve' where the many pairs were connected. Some cables were pressurised (usually the paper insulated lead covered cables) - others in later years were 'grease filled' to keep out the moisture.
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Old 4th Jul 2019, 3:19 am   #3
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Default Re: A question about overhead phone-lines.

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Originally Posted by Pellseinydd View Post
I have photos of the route plus a video of the little bit of telecoms history (No 36 in 'Great Pole Routes of the World' )
For some reason that reminded me of a film we saw at intermediate school about construction of the transmission line from Manapuori to the Tiwai Point aluminium smelter... and sure enough, it's available online: https://www.nzonscreen.com/title/the-line-1970
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Old 4th Jul 2019, 9:23 am   #4
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Default Re: A question about overhead phone-lines.

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Originally Posted by Pellseinydd View Post
The 'tube connector' would have been a 'jointing sleeve' where the many pairs were connected. Some cables were pressurised (usually the paper insulated lead covered cables) - others in later years were 'grease filled' to keep out the moisture.
I recall seeing the line chaps making a lead junction on one of those joints and attaching a mobile compressor to ventilate the lines. You also used to see odd little rectangular boxes on the poles which I was informed, contained inductances to compensate for line capacitance.
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Old 4th Jul 2019, 9:32 am   #5
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Default Re: A question about overhead phone-lines.

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You also used to see odd little rectangular boxes on the poles which I was informed, contained inductances to compensate for line capacitance.
Loading (or Heaviside) coils. They maintained a reasonably flat line circuit response over the 300-3400Hz range.
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Old 4th Jul 2019, 4:53 pm   #6
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Default Re: A question about overhead phone-lines.

Hi Ian, what I would like to know, and perhaps the OP too, is when did the GPO begin the wholesale replacement open-wire drops with the CCS figure-of-eight pairs in suburban streets?

I would guess our street was rewired between 1960-1965, but childhood memories can be deceptive.

My recollection was that all the drops on a given DP were renewed at the same time.

Incidentally, our exchange was MRCHE, one I know you have worked at.
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Old 4th Jul 2019, 5:29 pm   #7
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Default Re: A question about overhead phone-lines.

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Hi Ian, what I would like to know, and perhaps the OP too, is when did the GPO begin the wholesale replacement open-wire drops with the CCS figure-of-eight pairs in suburban streets?

I would guess our street was rewired between 1960-1965, but childhood memories can be deceptive.

My recollection was that all the drops on a given DP were renewed at the same time.

Incidentally, our exchange was MRCHE, one I know you have worked at.
I doubt you could say a particular date as it wasn't done as a 'nationwide' project. I know there were still ring type DP's (with double 'J' spindles and two insulators and all bare copper wires still in use in the late 1980's. There was one in Hereford with about 15 pairs and not a single dropwire!

Not sure where MRCHE (without looking through my '1144') other than Manchester Telephone Area. I may have visited it on a Sunday in the mid 1990's on my tour of most of the exchanges between the Mersey and the Scottish border 'acquiring things of interest' - thanks to BT for providing me with a TO (Technical Officer) and a Transit van. Most of my GPO years were spent deep underground looking after a major hub of the Defence Telecoms Network way west of Manchester.
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Old 4th Jul 2019, 6:01 pm   #8
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Default Re: A question about overhead phone-lines.

MR/CHE Cheetham Hill if I recall
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Old 4th Jul 2019, 6:27 pm   #9
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Default Re: A question about overhead phone-lines.

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Originally Posted by arjoll View Post
Quote:
Originally Posted by Pellseinydd View Post
I have photos of the route plus a video of the little bit of telecoms history (No 36 in 'Great Pole Routes of the World' )
For some reason that reminded me of a film we saw at intermediate school about construction of the transmission line from Manapuori to the Tiwai Point aluminium smelter... and sure enough, it's available online: https://www.nzonscreen.com/title/the-line-1970
That reminds me of a network of PAXs I looked after at Dinorwig Power Station in the late1970's/early 1980's - it was the largest civil engineering contract ever issued by the UK Government it the time. The Power Station was half a mile into a mountain Elidir Fawr (924m - 3031ft high) and 2500 ft below its summit. The power station was built in two caverns nearly 200ft high, 75ft wide and 600ft long which I was lucky enough to see just lit with a line of lights along the roof before the multistory power station was built in them. One of the oddest places I've ever looked after a telephone system. There was a 100 line AT&E PAX just outside the main lakeside tunnel entrance with a 50 line AT&E PAX mounted in an old railway van body held down with steel cables at 650 m (2132 ft) above the old slate quarry on the mountainside. At the highest point . Then there was a 25 line AT&E PAX up by Marchlyn Mawr reservoir reached by driving up the tunnel from the 50 line PAX location (at the top of a vertical shaft used to get the water down to the power station below) to the upper reservoir of the pumped storage scheme. On the top left above the quarry in this photo with the 100 line bottom left just outside the tunnel entrance.. The PAXs were all interlinked with tie-lines. The distance between them was very little as the crow flies but took some miles to drive up the mountain side on rough tracks. When the contract came to an end, I was contacted by the contracts MBZ who asked if I'd 'like the PAXs?' knowing of my interest in Strowger. Sadly I hadn't the room and they went for scrap

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Old 4th Jul 2019, 9:17 pm   #10
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Default Re: A question about overhead phone-lines.

In 1954, I was 10 years old, living in a village 6 miles south of Birmingham. One of our seasonal games was the making and flying of newspaper kites. There was only one house with a telephone and this had two bare copper wires running across the road between pairs of porclain insulators. If I remember right, getting the tail of the kite wrapped tightly around the two wires resulted in a bell ringing in the house and children runnning away. Is this how they worked then? pete
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Old 5th Jul 2019, 8:57 am   #11
Dave Moll
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Default Re: A question about overhead phone-lines.

I would have thought that shorting out the line would (at most) cause the equivalent of "bell-tinkle" rather than causing the bells to ring.
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Old 5th Jul 2019, 2:36 pm   #12
carnivalpete
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Default Re: A question about overhead phone-lines.

>Dave - You are absolutely right - I should have called it bell tinkling rather than implying continuous ringing. It nonetheless amused us as children as this happened every time the wind caught the tangled kite. pete
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Old 5th Jul 2019, 2:49 pm   #13
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Default Re: A question about overhead phone-lines.

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Originally Posted by Pellseinydd View Post
Most of my GPO years were spent deep underground looking after a major hub of the Defence Telecoms Network way west of Manchester.
Anywhere near Nantwich?
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Old 5th Jul 2019, 4:44 pm   #14
G6Tanuki
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Default Re: A question about overhead phone-lines.

Some fascinating observations: yes indeed the setup at my parents' house was a party-line - as well as the 2-core cable from the pole to the insulator on the house there was an earth-connection to a rod outside the lounge window. This was made in uninsulated twisted-strand copper wire and over the years acquired quite a few 'bodge' repairs using choc-block type connectors after various gardening accidents.

The overhead cable was black and like a rectangle-with-rounded-off-corners in cross-section, - like the sort of cable used on modern table-lamps - and it was looped round the upper flange of the insluator then bound with what looked like black PVC-coated single-core wire.

It was later replaced some time in the 1970s by the more-modern grey "figure-of-8" type that was tied-off to the metal insulator-bracket using one of the twirly pigtail things. By that time we'd gone from party-line to dedicated line - I guess concurrently with the exchange-upgrade that took us from 4- to 6-digit phone numbers?
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Old 5th Jul 2019, 7:52 pm   #15
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Default Re: A question about overhead phone-lines.

GPO/BT were still training apprentices how to run and tension open wires in the early 70.s also how to install drop wire and aerial cable joints. but not how to make up a lead joint.
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Old 5th Jul 2019, 10:25 pm   #16
Pellseinydd
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Default Re: A question about overhead phone-lines.

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Quote:
Originally Posted by Pellseinydd View Post
Most of my GPO years were spent deep underground looking after a major hub of the Defence Telecoms Network way west of Manchester.
Anywhere near Nantwich?
No. That was a minor place compared with the comms we had. We had an approx. 20 position sleeve control manual board with a couple of hundred lines to various corners of the UK - 24 lines to Whitehall alone plus others to Northern Ireland, Scotland etc. Plus a complex of telegraph equipment - more teleprinters than the rest of the telephone area put together. Hence we were trained on just about everything that the GPO had. We did have a line to the bunker at Nantwich but our location had been built before WW2 in anticipation of the war.
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Old 5th Jul 2019, 11:34 pm   #17
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Default Re: A question about overhead phone-lines.

My formative transmission days were spent deep in a cave in the Scottish highlands. We had a couple of 4MHZ coax systms to various security places in th UK, and systems nding up in places in the states or Canada. The older place had blast doors ,that we shut before going on duty.
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