PARTY LINES

An Overview

The Party Line or as it is officially known, Shared Service, is a complex subject and changed over the years as technology progressed.

This is where more than one subscriber shared a line.  It was generally used to reduce costs on line plant and later exchange equipment.

Whilst the customer may have a reduced line rental, they complained about the inconvenience especially if the other party was using the phone a lot.

The first shared lines were on the old manual exchanges and the switchboard operators would have to ring the lines a number of times depending on how many were sharing.  In the US, where lines could reach 20 miles in length this was quite common, but it also allowed others to listen in as all the phones rang.  But, because many of them knew each other, they also arranged conference calls so they could all chat and get the local gossip.

In the UK some shared lines could have up to 10 subscribers on them, but only one person could be involved on a call.  As the line circuit consisted of two wires the sharers would be split so that half of them would use one wire and the other half the other wire.  But that was just for incoming ringing and the speech aspect would be shared by all.

The telephones on Ten-Station Party Lines would be connected as follows:-
Stations 3, 5, 7, and 9, should be connected up as Station 1; Stations 4, 6, 8, and 10 as Station 2.

The exchange numbers on Ten-Station Party Lines would be allocated as follows:-
Stations 1, 3, 5, 7, and 9 will be given the circuit number with the addition of X1, X2, X3, X4, and X5 respectively.  Stations 2, 4, 6, 8, and 10 similarly have the same circuit number with the addition of Y1, Y2, Y3, Y4, and Y5.

E.G. a number 20X5 would equate to exchange number 20, station 9.

When requesting to be connected the caller would ask the switchboard operator, for example, 20X5 and the switchboard operator would then ring the X wire of number 20, five times.  You can see these numbers in old telephone directories.

As Automatic systems were introduced then sharing caused a problem as the exchanges in the UK could only differentiate between the two wires and Party Lines then just consisted of two customers.  To make an outgoing call you just lifted your receiver and dialled.  Incoming calls could differentiate between the two as there were two wires, so the right phone would ring.  Because there was no differentiation on outgoing calls the two parties had to negotiate the bill!  That did not go down to well!

The automatic systems were later designed so that when an outgoing call was to be made a button was pressed to get dial tone.  This differentiated the two lines and it was called the Separate Metering System as each party had their own meter in the exchange.

In the early 1970's the 1+1 Carrier System (WB 900) was introduced.  This allowed two customers to share a line in complete secrecy from one another and no press button.  The Carrier system used a higher frequency for one party so they could not hear each other and each phone only rang if their line was called.  Click here for more information on the 1+1 Carrier System.

This system continued to be in use until the late 1980's when System X and System Y exchanges were introduced into the UK and these systems did not provide for Shared Service.

The Carrier system was then used solely as this worked on a standard exchange line.  Not really Shared Service but in principle two people shared the circuit.

Click here - for a technical description of the separate metering system.

Click here - for details of the WB900 1+1 Carrier System.

Last revised: December 04, 2024