What Was A Party Line ?

What Was A Party Line ?

A party line was basically a way to share a phone line.

There were originally two types of party line on the automatic system.

1 – Common metering – where they both shared the same line circuit but had separate ringing to earth via either the B wire or the A wire (X and Y subscribers). To make a call on this system, the handset was just picked up and the call was dialled.

2 – Separate metering – where each party had their own line circuit but the earth was removed from the K relay contact preventing a loop from seizing the line circuit. Each subscribers telephone was fitted with a ‘Call exchange’ button. This earthed the appropriate A (Y party) or B (X party) wire to seize their line circuit (and hence effect metering on their meter). Ringing was still individual to each subscriber – the only common bit being the subscribers number from the selector multiple – with a cross to make put the ring current on the opposite wire for the ‘Y’ party.

There was no privacy. If one of the users was making a call, and the other picked up, they would hear the conversation (and be heard). Later on, a technology called WB900 came along. This shared the pair, by having a conventional DEL “audio” and a “carrier” sub, whose service was provided by a radio carrier down the pair. The transmitter/receiver at the carrier subs house, had rechargeable cells which were charged by the “Audio” subs line.

There was privacy and both parties could use the phone at once. However, if the Audio subscriber used his phone a lot, the carriers battery tended to go flat….

Later on, a fully digital system came along “DACS” which, digitised the pair between the exchange and the teeing point, for both customers. It does the job a treat for plain old telephony.  These were notorious for capping the maximum speed people could expect from their analogue modems, while surfing the net, ie 56k modems would only run at 28k. The only thing that was shared in a party line was the pair of wires from the exchange to the Cabinet (the green box in the street and the point at which the pressurized main cable from the exchange MDF is terminated on the ‘E’ side) This was only applicable to ‘Separate Metering’ – ‘Common Metering’ used a single line circuit as well as a ‘common’ cable pair.

Pairs were also shared as far as insulators on the pole route from the DP – not just to the ‘green Cabinet’.

“Inserts, Insulator – used inside Insulators No 16 and 22 when teeing shared service lines – See E.I. Lines Overhead E 3139”. The Insert was a round black composition block with a brass insert which accepted three wires at 120 degree spacing – the 40lb cadmium copper line wires.

Shared Service was provided for 2 reasons:-

1) Shortage of mains back from the PCP/SCP (Cabinet/Pillar) and was the most common.

2) Shortage of exchange equipment, that gave exclusive use. This meant the sharers were anywhere on the exchange area.

The term Party Line applied to more than 2 customers in rural, manual areas, and these had been removed once the exchange went auto. In a copy of the Service Instructions for 8/63 they are already shown as obsolescent. Even requests to take over a Rural Party Line were refused from 1961 onwards.

From what I was told by someone who worked in sales (1968-1972) they were instructed not to refer to Shared Service as a Party Line.

In the 1950/60’s Shared Service was provided by two further different types :-

1) Common Metering. If there was poor earth return then a bell set 41 was provided, at both properties, and the two customers had to agree their portion of the bill. There only being 1 meter. This form had been eliminated by the late 1950’s.

2) Separate metering. There was good earth return and the button seized the equipment and the relevant meter recorded the calls.

Good earth return was achieved by attaching wire to the lead water pipe coming into property an alternative was to drive a spike into the ground outside and attach it to that.

Liability to share.

Some Residential customers were not liable to share. Those who had had service prior to January 1948 were exempt. If they moved then they started out afresh at the new property, though.

All other Residential installations had a box completed on the providing/transfer advice note with the letters PP (Potential Party) entered (even though we were not allowed to refer to it as Party Line). That was recorded by the Routeing Officer on the Line Plant records to show this installation was liable. There were 2 other ones that come to mind and there may have been more. USS meant the installation was Unsuitable for Shared Service. Could have had a coin box, burglar alarm connected via block terminal, subs private meter etc.

Then there was VSS who was a voluntary sharer. They used the ‘phone very little and liked the 10 shilling (50p) reduction in rent in 1960’s. It later increased to £1 difference.

When a Line Plant enquiry form or call to the ‘Router’ was made and there were no pairs left he would supply a list of all the PP subscribers’ on that DP, if that was where the problem was. In the case of the ‘Cab’ having no mains we would look for a shared line that currently was without a partner. If there happened to be a ‘stop’* installation then that could be utilised or it meant selecting the person who had been connected the most recently and sending them a letter. If no response then an appointment would be made and both customers notified of the date. If the person, to share, obstructed the change then they were informed that service could be withdrawn and they normally then agreed.

* Stop is where the line is still connected and line plant exists but it is out of service in the exchange.

Many thanks to all the people from various telecoms groups who helped Duncan from SystemTek to compile this document.


Duncan Newell

Duncan is a technology professional with over 20 years experience of working in various IT roles. He has a interest in cyber security, and has a wide range of other skills in radio, electronics and telecommunications.

One thought on “What Was A Party Line ?

  • October 7, 2016 at 3:41 pm

    Thanks just what I was looking for


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