Bare wire phone lines

[Keith956]

I recall back in the 60's the phone line was a pair of bare wires, separated by several inches, from the pole to porcelain insulators on the eaves. The wires always used to 'sing' in the wind, I always liked the sound.

When were they replaced by the modern insulated cable?

[G6Tanuki]

I suspect the single-uninsulated-copper wires and separate insulators became extinct for new installations in the mid-50s.

My parents' house was built in 1957 and only ever had the "single" phone-cable [actually two cores in an oblong plastic sheath] fitted from the start.#

If you look at immediately-post-WWII-vintage movies though, you still see a load of the old-style separate-wires-and-insulators-on-crossbars, specially along railway-lines!

[Roger Ramjet]

Hi Keith,

Yes OPEN WIRE distribution I remember being taught how to re tension these at the GPO training facility in Glen Parva Barracks, Leicester circa 69 or maybe 70.

At that time there were still a few existing but they were being phased out for the grey plastic coated drop wire.

Ironically one of the fellow trainees complained that the wires to his parents house were constantly having to be re tensioned instead of being swapped out for drop wire which would have sorted the the problem once & for all.

Also very easy to get a tingle via ears [if ringing voltage present] when working at the top of a pole !

Rog

[Granitehill]

When I joined the GPO as a technician apprentice in 1965, one of my first work experiences was as a member of external wiring and cable gang. The major task was to replace open-wire pairs of 40 pounds per mile cadmium copper with plastic insulated twin known as "drop wire" or "Dropper". This became the standard for subscriber local ends (distribution pole to house). The primary reason was economic - far lower installation and maintenance costs.

The days of open wire weren't over, though. It was around until the 1970s for specialised uses such as inter-exchange junction circuits and the railways used the same kit for trackside signalling circuits. It was almost always cadmium copper with gauges of 70, 150 and 300 in pounds per mile. (It is often called "Hard drawn" by radio amateurs, but in reality it was all hard drawn. Only the telephone wire had the few percent of cadmium which greatly improved it's properties under tension). It also hung on for years as open wire RF feeders at the big HF stations. I think Rugby Radio used gauges up to 600 LB per mile between the big transmitters and the rhombic aerials.

Drop wire wasn't all grey - that was the thinner (cheaper) stuff and a bit of a liability as it was copper plated steel, and prone to rust through where the insulation got abraded. This became black polythene-coated cadmium copper, and eventually morphed into the multi-pair steel-reinforced stuff used these days.

The redundant ceramic insulators are still to be seen occasionally, where the people installing the replacement drop wire didn't bother to remove them. These were known as "16s" (Insulator number 16). They are very strong and ideal as base insulators for HF verticals should you find any lying about...

[Tim]

One does still come across the old grey twin stuff ( dropwire 4 I think)these days. We do try to replace it( on installs) as it is not very good for broadband. Believe it or not there are still a very few open wires from pole to house still remaining. A couple of years ago I went to a fault at a customer off an exchange near Bath, who still had them. He was getting 65Mbps! The fault was internal, and he was happy to leave his wires as they were.

[cmjones01]

An air-spaced copper pair will have a nice low loss, so I'm not surprised it worked well for broadband. The very best microwave cables, used for laboratory measurement and calibration, are also air-spaced for a reason.

Chris

[paulsherwin]

Originally Posted by Granitehill

The redundant ceramic insulators are still to be seen occasionally, where the people installing the replacement drop wire didn't bother to remove them. These were known as "16s" (Insulator number 16). They are very strong and ideal as base insulators for HF verticals should you find any lying about...

The pole outside my house still has the insulators around the top, though others in the same street have had them removed at some stage.

[60 oldjohn]

When I was at school one of the lads in my class knew where there was some phone cable in a ditch, would I like it? YESSS please, it would make a good shortwave aerial. When he finally remembered to bring it it was all taffled up in a ball. It was two single conductors maybe 1.5mm diameter, the black insulation was figure of 8 or rather two square sections side by side. The wire was strange stuff silver in colour and very springy. This would have been around 1969 I would expect GPO were replacing wires and dumped this as it took me quite a while to un-tangle it all.

John.

[Keith956]

Interesting info, thanks. Parents house was built in 1957, we moved into it in 1960, I believe the old bare wires were there until the mid 70's.

We were also on a party line, was strange to pick up the phone sometimes and hear the neighbour!

[See_Mos]

My first job from 1967 to 1970 was quality control at a factory in Wakefield and we were still drawing cadmium copper conductors for the P.O.

[theredhouseinn]

As an old boy I remember the twin conductors on the porcelain insulators.
In the 60's I studied the telecom tech cert at Reading college and the first year was telephony telegraphy and if I remember correctly the spacing and wire diameter was to retain the 600 ohms impedance. 138 X log base 10 X distance between the wires divided by the diameter of one wire.
John.

[Roger Ramjet]

Sure I recall that in certain locations, the open wires had what looked like cork bottle stoppers fitted at regular intervals - presumably to protect large birds from flying in into same. Maybe called "game guards" ?

Rog

[John M0GLN]

Originally Posted by Keith956

I recall back in the 60's the phone line was a pair of bare wires, separated by several inches, from the pole to porcelain insulators on the eaves. The wires always used to 'sing' in the wind, I always liked the sound.

Bare wires, so that's the reason for singing phone lines, I liked that sound as well but since moving to Southport in the mid fifties I've never heard it as all the towns telephone wires are underground.

John

[Hartley118]

Originally Posted by theredhouseinn

As an old boy I remember the twin conductors on the porcelain insulators.
In the 60's I studied the telecom tech cert at Reading college and the first year was telephony telegraphy and if I remember correctly the spacing and wire diameter was to retain the 600 ohms impedance. 138 X log base 10 X distance between the wires divided by the diameter of one wire.
John.

It's fascinating that the '600 ohm impedance' of historical telephone connections still retains such prominence today in an audio world which has never encountered open conductors on porcelain insulators. Some audio engineers still seem to attribute a kind of mystical significance to a 600 ohm analogue audio termination impedance when the typical characteristic impedance of twin-screened audio cable is nearer 100 ohms than 600 ohms.

Of course, with analogue audio, considerations of cable characteristic impedance and termination impedance are generally only relevant for the distances involved in telecoms work in order to avoid audible reflections. I'm therefore intrigued by the apparently seamless transition which happened in the 20th century telecoms industry from open wire 600 ohm circuits to paper insulated (and more recently polythene insulated) twisted pairs. Were termination impedances changed? Were there reflection problems? And, recognising that some terminations were by default just an ordinary telephone, what's a typical phone impedance and was it changed when open wire circuits were discontinued?

Martin

[Tim]

It was two single conductors maybe 1.5mm diameter, the black insulation was figure of 8 or rather two square sections side by side. The wire was strange stuff silver in colour and very springy.

That sounds like Dropwire 8. It was used for long runs( low loss/resistance) and, in those days, lines crossing under / over high voltage(>1000v) due to its thick insulation.
Later versions had blue sheathing. Available until about 10 years ago until superseded by Dropwire 12 which has a twisted pair of 0.9mm dia conductors in round black sheathing. Outside diameter approx 6mm. Still used for the rare occasions when lines cross HV, long spans etc.
AFAIK 12 was introduced so that it and “ normal” dropwire 10/10G were the same outside diameter to make them both compatible with current joints and closures.

[DrStrangelove]

Originally Posted by Roger Ramjet

Sure I recall that in certain locations, the open wires had what looked like cork bottle stoppers fitted at regular intervals - presumably to protect large birds from flying in into same. Maybe called "game guards" ?

Rog

I remember those around here.

I seem to recall that they were loading coils.

[Roger Ramjet]

Originally Posted by Tim

That sounds like Dropwire 8. It was used for long runs( low loss/resistance) and, in those days, lines crossing under / over high voltage(>1000v) due to its thick insulation.
Later versions had blue sheathing. Available until about 10 years ago until superseded by Dropwire 12 which has a twisted pair of 0.9mm dia conductors in round black sheathing. Outside diameter approx 6mm. Still used for the rare occasions when lines cross HV, long spans etc.
AFAIK 12 was introduced so that it and “ normal” dropwire 10/10G were the same outside diameter to make them both compatible with current joints and closures.

The fitter I trained with called it "HV BLUE"' & also used on shared poles provided for telephone & mains electricity in rural locations. The HV BLUE was always about a yard lower than the the electricity cables for obvious reasons. Secured at both ends by a wedge type clamp to match he thick insulation rather than the usual drop wire wrap around thingy's.

[duncanlowe]

My Parent's previous house was built in the 60's. No overhead lines, they were all buried.

There was a little cast (aluminium?) post in every few gardens, where the cable to each property were spliced in.

I don't think the cables were ducted as when there was a fault in the street, it had to be dug up to fix it.

[Roger Ramjet]

Originally Posted by duncanlowe

My Parent's previous house was built in the 60's. No overhead lines, they were all buried.

There was a little cast (aluminium?) post in every few gardens, where the cable to each property were spliced in.

I don't think the cables were ducted as when there was a fault in the street, it had to be dug up to fix it.

Takes me back Duncan to when I bought a brand new house in 1975 which had the same arrangement. As you suspect there were no ducts i.e. the UG cable was SWA for protection & trenched in by the builder as a joint venture with BT [who provided the cable]. The cast alli box was called a "Jointing Post", & conductors were gel crimped. Each cable had two pairs similar to current generation drop wire.

[TowerRadio]

We still have the bare wires connecting our house to a pole in the back alley.I recently removed the last portion of downlead when repainting.The BT connection hasn't been used since 2009. Can you use one of these wires as an aerial for a crystal set? Les