Britain: An official handbook > 1977

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BRITAIN 1977: AN OFFICIAL HANDBOOK
million telephone calls were made comprising 13,736 million local calls, 2,356
million trunk calls and 92 million international calls.
Hull District Council is the only local authority to exercise its option of
operating its own service under licence from the Post Office; this service is
connected to the Post Office trunk network.
The first operational electronic exchange in Europe was opened at Amber-
gate, Derbyshire, in 1966. There are now over 700 such exchanges in Britain.
Mobile electronic exchanges were introduced in 1973 and the first of a new
series of electronic telephone exchanges, with capacities of up to 40,000
lines, was brought into service in Birmingham in February 1976. Pulse code
modulation systems are being used to increase the circuit capacity of lines
on routes between exchanges.
International subscriber dialling operates from London and most other
major cities to 32 countries including most of western Europe and a number
of countries outside Europe. The Post Office is engaged in a five-year pro¬
gramme costing ^250 million to expand Britain s international telephone
exchange network. The Edgware international exchange in London is the
largest of its kind in the world. Calls to Europe are connected via cable and
microwave radio links, and to countries outside Europe by way of trans¬
atlantic and Commonwealth cable networks, communications satellites and
high frequency radio systems.
A radio tower, 620 feet (189 metres) high, in London provides microwave
radio links for carrying long-distance telephone and television circuits. There
are about 200 Post Office communications masts and towers in use.
Special Telephone Several specialised services are available by telephone, including the 999
Services emergency dialling service enabling subscribers to be connected as quickly
as possible, and free of charge, to the police, ambulance or fire brigade
services. A public radiotelephone service operating in several areas enables
users of vehicles fitted with suitable equipment to make or receive calls to
or from any telephone in the British network. Initial trials are in progress on
‘viewdata’, a service in which a telephone subscriber calls a centre to obtain
information which is displayed on his television screen or on a special screen,
full-scale trials are planned to start in late 1977. Recorded information
services include: the speaking clock, weather forecasts, motoring information,
recipes, cricket scores, binancial Times Share Index and Business News
Summary, and ‘Dial a Disc’. In London a recorded service provides details
in five languages of events taking place, and a similar service, in English only,
is provided in Edinburgh during the summer.
Submarine There are some 25 submarine cable systems between Britain and the continent
Cables of Europe and five between Britain and North America, covering a total of
about 17,800 nautical miles (33,000 kilometres). Cable systems using tran¬
sistors in place of thermionic valves have been developed and refined by
British manufacturers in consultation with the Post Office Research Station
and are used in all new systems. A comprehensive Commonwealth telephone
cable plan, completed by 1967, involved the construction of three long¬
distance telephone cable systems covering a total of 17,3°° nautical miles
(32,100 kilometres). Subsequently there have been large increases in the
capacity of new submarine cables—a cable to France installed in 1976 has
3,400 circuits and one to Belgium, which will be laid in I977> have 4,000
circuits. The Post Office acts as a consultant to overseas administrations
on the installation of submarine cables.