Post Office Telephones

Background

At the start of the Cold War, the General Post Office (GPO) was a Government department responsible for all communications in the United Kingdom. The letter and parcel business became Royal Mail and the electrical communications became Post Office Telephones and was privatised into British Telecom.

In the 1960's and 70's the UK telecomm infrastructure was very different from today's complex telephone networks. The network was exclusively run by the Post Office. It was not until the 1980's that other companies were allowed to provide telephone services. The Post Office, as a Government department was starved of money by the exchequer. Many users had party lines, which meant that two houses would share the same wires to the exchange, although they had different numbers, there was no privacy between parties. Waiting lists were common and there were even television adverts discouraging the use of the telephone.

When I became an apprentice, I was amazed to see the toilet paper was like tracing paper and had 'Government Property' printed on each sheet. The soap was called 'White Windsor' and had an 'ER' stamped into it. My notebooks a pencils were supplied by the Stationery Office and had 'ER' and Crowns on them too.

Land Line Communications

Until the 1980's the Post Office (PO) had almost exclusive rights to provide landline based communications systems. They ran the whole of the public telephone system. A separate public teleprinter network. Their own teleprinter network for sending Telegrams between telegraph offices. Some large companies had their own internal telephone systems, which still relied on PO lines to connect between offices. These were known as private circuits. This meant the renter had exclusive use of the wires provided their premises by the PO. Television pictures were carried on PO cables from studios to transmitter sites. The general public had little perception of the work of the PO, thinking all it did was provide the telephone and postal service.

It made sense that the PO would provide all landline based Military and Civil Defence communications too. The WB400/WB600, Royal Observer Corps networks and the Emergency Manual Switch System are examples covered in topics elsewhere on this site, linked from the bottom of this page.

The military had thousands of point to point private circuits provided by the PO. These were not secret as such. Records existed in all exchange through which the circuits passed so faults could be rectified. However the records did not reveal what the circuit was used for. A simple code system made it awkward to locate the two ends from somewhere in the middle. At the Kelvedon Hatch RGHQ Bunker museum, a display indicates its code was 'QMET' when operational. I knew Bawburgh RGHQ 4.1 only as 'QETN', somewhere near Norwich as this was the last identifiable exchange, but that was all.

PO Microwave System

Over the years there has been much speculation of the purpose of the microwave system, consisting of chains of towers across the countryside every 30 miles or so. The London 'Post Office' now 'BT' tower being the one familiar to most people. At the time, microwave links each carrying 600 telephone channels offered a cost effective alternative to laying long distance copper cables.

It certainly was used for carrying Television, Telephone and Private circuits over long distances. However devious military or spying purposes are suggested by some authors. The web site dedicated to Cold War buildings www.subbrit.org.uk which is linked from my Main Topic Index page carries an account of the 'Backbone Microwave Towers' which I believe to be accurate.

Secret Underground Exchanges

Three underground exchanges were built in the 1950's which were classified until the 1960's. These were designed to withstand a Hiroshima type blast, but as atomic weapons became more powerful they became useless. There are a number of websites dedicated to these units. Use a search engine to look for 'Birmingham Anchor', 'London Kingsway' or 'Manchester Guardian'. Bear in mind that some sites do tend to guess at the true facts, again subbrit does carry some good information.

Hardened Repeater Stations

The connection between the home telephone and the exchange is carried on a single pair of wires. Over the relative short distances involved, it is economical to bundle these together in large cables, some containing 2000 wires. Over long distances, the use of large cables is not economic. A system of multiplexing 24 analogue speech channels into two pairs of wires was developed. Further developments increased this capacity. By the 1970's a 4Mhz co-axial cable could carry 960 channels on two coax tubes. Today 40Ghz optical fibres have 10,000 times this capacity.

When a single telephone call is sent down a long pair of wires between exchanges, it must be amplified at regular intervals. The amplifying point is called a telephone repeater station (TRS). Most large Automatic Telephone Exchange (ATE) buildings incorporated a repeater station. On long distance routes, the multiplex equipment at each end was housed in the repeater station rather than the exchange part of the building. Coax cables carrying television or multiplexed speech channels required amplifying every couple of miles. Where no suitable exchange building existed, a repeater station in a small brick building the size of a garden shed was built.

At some locations such as Rothwell Haigh in Yorkshire, special hardened repeaters stations were built to house the terminal equipment, this served a now disused RAF communications centre, and has been sold off.