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Events in telecommunications history

1920

G A Campbell, an American, invented the anti-sidetone telephone circuit. In the older type of telephone circuit the power from the transmitter was divided between the line and the local receiver, so that the caller heard his own voice. This was called ' sidetone'. In the circuit which G A Campbell devised this unwanted current was considerably reduced, leading to greater efficiency.

Private Automatic Branch Exchanges (PABXs) were introduced.

The first wireless telegraph point-to-point service was opened with the Continent.

A telephone conversation by wireless radio was exchanged on 19 August between Sir Samuel Instone of the Instone Air Line from a private residence in London to an aeroplane in flight to Paris. The plane was a Vickers G-EASI and was fitted with an AD2 pilot operated radio-telephone piece of equipment.

The Post Office commenced its long-distance radio-telegraph service to ships.

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