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NB This is a sub-section of General Post Office
of Dollis Hill, N.W.2.
Part of the General Post Office, which had a research branch from its early involvement in telephones.
1909 The Post Office Research Station was first established as a separate section of the General Post Office in 1909.
1921 the Research Station moved to Dollis Hill
During the 1920s work focused on the application of electronic techniques to telephony, including development of valve amplifiers to enable long-distance calls.
1933 The main permanent buildings at Dollis Hill were opened by Prime Minister Ramsay MacDonald.
1936 Development of the "speaking clock"
WWII The code-breaking Colossus computer, used at Bletchley Park during the Second World War, was built at the Post Office Research Station by a team led by Tommy Flowers. It was the world’s first programmable electronic computer. It contained 1,500 electronic valves and played a crucial part in cracking German codes during the second world war.
1946 Began to construct hardware for the Automatic Computing Engine to National Physical Laboratory's design but after a while the contract was ended. The Post Office continued to work on a computer based on the ACE design - this machine became MOSAIC, which went to Telecommunications Research Establishment at Malvern and worked for the Ministry of Supply there.
1952 Had developed electronic switching for telephone exchanges; trial at Richmond exchange.
1954 The trial of electronic switching at Richmond was recognized as a success and performed as well as electro-magnetic switching. Nevertheless much research and development was still needed before a complete system using electronics could be implemented
1960s Dollis Hill worked on introduction of reliable semiconductor-based repeaters which replaced the valve technology previously used for submarine telephone cables. Also pulse-code modulation underpinned a switch to digital technology throughout the telephone system. Optical fibre began to replace copper cable. Introduction of the Post Office's Viewdata service — later called Prestel.
Late 1960s the Post Office acquired part of the site of the decommissioned Martlesham airfield for its research laboratory which was moved from Dollis Hill.
1968 The Post Office installed the first example in the world of a pulse code modulated (PCM) exchange which was based on technology developed at Dollis Hill
1975 The research station was officially opened at Martlesham Heath, Suffolk.
The Post Office Research Station building at Dollis Hill has now been converted into 62 flats and is now known as 'Chartwell Court', with an access road called 'Flowers Close'.