Mobile telephones linked by radio

Early mobile radios

Radio communication systems faded into use over a period. By the 1920's, police forces in the USA were experimenting with two-way radios in patrol cars. Radios connected directly to the telephone network came rather later.

Radio telephones

After the second world war, a few radio telephones were fitted into the cars of the rich and important in several countries.

These units worked by connecting to one or more base stations, and were half-duplex (meaning that although the transmit and receive frequencies were different, you could either talk or listen, not both at once).

The transmitters had output powers of 20 or more watts, and the areas they worked in were restricted to the range of their signal.

But not too many of them!

Because of the wide channel spacing and high powers used, combined with the limited range of frequencies available, there was only capacity for a few thousand radio telephones across the country.

As with early fixed phones, calls had to be connected by an operator, and it was some years before automatic exchanges were widely introduced, though the first automatic mobile system went live in Sweden in 1956. There was no possibility of hand-portable units: these devices could run your car battery down if you weren't careful!

During the 1960's mobile telephone systems were available in parts of the UK (starting in Lancashire in 1959). The service reached London in 1965, using the Post Office Tower as a base.

Proper telephones

In 1964 the Bell System introduced the american Improved Mobile Telephone Service (IMTS). It was a full-duplex system – you didn't have to press a button to talk. Speech went to and fro just like a normal telephone. It offered direct dialing, automatic channel selection and reduced bandwidth to 25-30 kHz.

In the UK, full-duplex, direct-dial mobile telephones arrived with the launch of System 4. First launched in 1983 it gradually rolled out to cover most of the populated areas, but still using six regional 'zones'. It was not a national service.

This was a major step forward, but before wider use of mobile phones could be possible, some way of re-using frequencies had to be developed: this had been designed by Bell Laboratories in the USA in 1947, but was not fully implemented for another 20 years or so.

Cellular – room for growth

In the 1980's cellular mobile phone networks were being developed in several countries... See the Cellular page for the next chapter.

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