A manhole cover which says ‘POST OFFICE TELEPHONES’ looks like a bit of a mystery.

When the UK telephone system was being developed in the twentieth century it was completely under the control of the Post Office.

The name Post Office Telephones was used until October 1969 when the Post Office ceased to be a Government department. This new division in the The Post Office Corporation became Post Office Telecommunications in 1975.

Post Office Telecommunications operated as a division within the Post Office Corporation (a nationalised industry). The telecommunications part of the business was still very much under Post Office control,

In 1980 this division became British Telecom - part of the Post Office.

In 1981, Post Office Telecommunications officially became British Telecommunications a separate corporation.

In 1984 British Telecom became the trading name for the privatised company British Telecommunications plc - entirely separate from the Post Office.

In 1991 BT became the new trading name of British Telecommunications plc. The government no longer had any (significant) financial holding in BT, but the company was regulated by OFTEL ( OFfice of TELecommunications) which was appointed by the government.

Until the 1970s these things just didn’t exist:
    Battery phone
    Car phone
    Cellphone
    Cordless phone
    Digital phone
    Mobile phone
    Push-button phone
    Radio phone
    Smartphone

Before the 1970s all telephones were in a house, an office or a telephone box in the street and were physically connected to the telephone system along copper wires.

The number of telephone conversations which the system could support at any one time depended on the actual number of copper wires across the country.

Many of these wires between towns and cities ran alongside railway lines, supported on telegraph poles.

Telephones were equipped with dials. A telephone dial has a disc with ten holes.

The telephone dial generated a series of clicks or pulses down the line there being just ten different combinations of pulses. As the phone line was just two wires, the telephone dial was effectively a switch which switched on and off at about ten times a second.

The handset was connected to the base by a cord or wire.

How to use a rotary telephone dial: Click Here

Try it yourself

There were no plug-in telephones. The telephone itself was hard-wired to the incoming line and could only be installed by a Post Office engineer.

The telephone in your house was owned by the Post Office and you paid rent on the equipment in the same way as some people today pay rent for the phone line itself.

Getting a telephone installed in your house could take many months. In some places there were not enough physical telephone lines to a particular area and you might then have to use a ‘party line’. This was where two or more subscribers were connected to one telephone line.

Party lines did not provide secrecy from the other party, but they were arranged so that only the intended recipient's telephone bell rang for an incoming call. When a subscriber wished to make a call they had to operate a push-to-make switch on their telephone to signal to the exchange that they wished to make a call, this ensured that the exchange metering billed the correct subscriber.

A subscriber wishing to make a call had to wait for the other party to finish their call, if they were already on a call. If the call was an emergency they had to request the other party to end their call. Shared service was introduced on automatic exchanges in 1942 but ended in the early 1980's as the new System X digital exchanges did not have the facility for party lines.

So this is why we talk about ‘dialling‘ a telephone number or listening for a ‘dialling tone‘. Well, in the first half of the twentieth century, in order to speak to a particular person on a telephone you either had to use the telephone to speak to a ‘telephone operator‘ at the local telephone exchange or use a rotary ‘dial‘ on the telephone to enter a combination of letters and numbers - the recipent’s telepone number.

At that time we would refer to a person’s telephone number as an exchange name and a number so if you were using a telephone dial you would dial the first three letters of the exchange name followed by the actual number.

I was brought up in North West London in the 1940s, 1950s and 1960s. The area was then part of the county of Middlesex (which no longer exists as it became part of Greater London in 1965).

We were probably quite early in having a home telephone because my father was self-employed and worked at home.

EXPLAIN HOW MY PHONE WORKED

Our telephone had a dial so we were able to dial directly to any telephone in the London area. A London telephone number comprised three letters and four digits. Our telephone number was COLindale 1443. Anybody in the London area could call us by dialling the seven characters COL1443.

A school friend of mine lived in Stanmore on the Grimsdyke telephone exchange. His telephone had no dial. To make a telephone call it was necessary just to pick up the handset and the operator at the exchange would say “Number please”.

You could also dial three-letter codes such as TIM for the speaking clock, DIR for directory enquiries, TEL to send a telegram and UMP for the latest cricket scores.

Over the years telephone numbers have gradually been lengthened. In 1958 Subscriber Trunk Dialling (STD) was introduced. In London it wasn't introduced until 1961. So in 1958 a telephone subscriber in Bristol could have dialled 01COL1443 and got through to us.

In 1966 All Figure Numbers were introduced so you would no longer refer to a telephone number by its exchange name. Our number became 012051443. In 1990 that number would have become 0812051443. In 1995 it became 01812051443. In 2000 the numbers were changed once again so it would now be 02082051443.

Incidentally, until the advent of STD dialling zero would put you through to the operator. This was changed to 100 in 1958.