1912

On 1 January the Postmaster-General took over the system of the National Telephone Company at a cost of £12,515,264, inheriting 9,000 employees, 1,500,000 miles of wire and 1,565 exchanges - of which 231 had more than 300 subscribers each. The National Telephone Company provided for 561,738 subscribers altogether. Just under 70 exchanges were of the Central Battery type; most of the rest were of the magneto type.

For the first time a unified telephone system was available throughout most of Britain. From this date the Post Office became the monopoly supplier of telephone services with the exception of the remaining municipal services in Hull, Portsmouth and Guernsey. There followed a period of rapid expansion. In the next three years no fewer than 450 new exchanges were opened in places where there had previously been no telephone service.

The first experimental public automatic telephone exchange installed in the UK was opened for service at Epsom, Surrey, on 18 May. The equipment used was of the Strowger two-wire type and was supplied and installed by the Automatic Telephone Manufacturing Company Ltd of Liverpool. It had a capacity of 500 lines, and was the forerunner of the standard Strowger equipment adopted by the Post Office from 1922.

On 13 July another Strowger-type exchange was opened for service at the General Post Office, London. It was intended for Post Office use as a private branch exchange and was known as 'Official Switch'. Its equipment was for 900 lines, with an ultimate capacity of 1,500 lines, and it enabled GPO engineers to observe its technical performance and gain experience of its working.

The SS Titanic sank with great loss of life on 15 April after hitting an iceberg. But 700 passengers who would otherwise have been lost were saved as a result of a distress call by wireless telegraphy.

1913

The telephone system provided by the Corporation of Portsmouth was transferred to the control of the Post Office in Great Britain, leaving the Post Office as the only provider of a telephone service, other than Hull Corporation and the States of Guernsey.

The first 'Keith Line Switch' non-director exchange with remote manual board was opened at Chepstow ).

1914

junction telephone service was inaugurated between Liverpool and Manchester.

submarine telephone cable was laid between Dover and Dunkirk.

A telephone service was opened with Switzerland.

Hull Corporation's licence to operate a local telephone service was renewed on the understanding that the Corporation would purchase the ex-National Telephone Company's nine exchanges in the area for £192,423. These, together with responsibility for 9,126 stations and 197 call offices, were transferred to the Corporation.

The third automatic telephone exchange in this country was opened at Hereford on 1 August. The Lorimer system, as it was known, was built by the Canadian Machine Telephone Co and had a 500line capacity. It had been patented in the United States by E A Faller (US Patent No. 686892) for a 'well-designed mechanism performing a definite cycle of operations and driven by some source of power'. The power source used was, in fact, a constantly revolving shaft with a mechanical clutch, comprised of toothed wheels, brought into operation by an electro-magnet. The 100-point rotary switch with switched 'wipers' (part of the selecting device) passed over the contacts in one direction only. An unusual feature of this system was a lever-calling device on the telephone on which the caller composed the number by adjusting the levers. The caller could see and check the number before turning a crank and lifting the receiver to set the calling mechanism in operation. The subscriber could pay for two, three or more number composing levers, allowing the selection of local, intermediate or longer distance calls. Hereford was the only exchange of the Lorimer type installed in this country and remained in efficient working order for more than 11 years. Ultimately, the Post Office decided on the Strowger system as its standard in 1922.

Western Electric Company Rotary type automatic exchange was opened at Darlington for public service on 10 October. It was similar to the Lorimer system in the use of power-driven selector switches, but it featured the 'Register', a device to receive the subscriber's signals from a rotary tenhole dial and to store them for subsequent control of the switches.

Another exchange of this type was opened at Dudley on 9 September 1916 - but with the adoption of the Strowger system as the Post Office standard automatic exchange in 1922, it saw little further service in this country, although it was popular in Europe.

1915

The 'Archangel' submarine telegraph cable was laid between Great Britain and Russia.

1916

The Post Office made the first effective use of amplifiers on telephone circuits when research staff installed experimental repeaters in the London to Belfast and London to Dublin circuits at Liverpool. A few weeks later, the first permanent repeaters were installed in the London to Liverpool cable at Birmingham. The installation of these vacuum tube repeaters was the first commercial use of such equipment.

HMTS Monarch (No. 3) of 1,150 tons joined the Post Office Cableship fleet, remaining in service until being sunk in April 1945 off Southwold, Suffolk. She had already seen damage the previous year in 1944 when she was mistakenly shelled by an American destroyer.

1917

A bomb dropped by enemy aircraft struck the Central Telegraph Office on 7 July. Damage was caused to the South East corner of the fourth floor. A section of the roof parapet fell down and killed a soldier on sentry duty in the street, but no Post Office people were injured. A journalist who witnessed the attack later claimed that the bombing of the CTO was 'the only instance of a direct hit by German raiders of an object they aimed at'.

The London-Halifax (Nova Scotia) direct cable telegraph link was established, using syphon recorders and Judd & Fraser direct printers. The cable was purchased by the Post Office from the Direct United States Company and opened for traffic on 18 July.

A telephone junction service was opened between Edinburgh and Glasgow on 1 April.

1918

Leeds automatic telephone exchange was opened on 18 May in Basinghall Street - a Strowger-type manufactured and installed by the Automatic Telephone Manufacturing Company. It was the largest of its kind in Europe, equipped for 6,800 lines with an ultimate capacity of 15,000, and the first exchange in this country capable of being extended to give service to 100,000 subscribers. It was also the first in which the caller was required to dial five figures for every local call.

HMTS Alert (No. 2) of 941 tons and of similar design to Monarch (No. 3) was launched. Like her sister ship she gave faithful service during World War II, but was sunk with all hands in February 1945 off the North Goodwins.

Siemens Brothers & Company type automatic exchange was opened at Grimsby on 14 September 1918. It was similar to the Strowger system in many respects, but differed in the form of line switch employed and because the connectors were controlled entirely by relays. The characteristic feature was the 'Preselector', a rotary line switch provided for each subscriber's line to find a disengaged trunk to a selector.

Further Siemens type exchanges were opened at Stockport on 23 August 1919 and at Southampton on 30 June 1923, but the Post Office had decided on the Strowger system as its standard automatic exchange in 1922.

The Wireless Telegraphy Board was set up to coordinate interference problems in radio communication in the English Channel, thereby beginning the frequency management structure that exists today.

The first interdepartmental committee to be established in the UK, the Wireless Telegraphy Board reported back to the Imperial Communications Committee on national (domestic) communication matters. With the outset of World War II, it became a military board known as the British Joint Communications Board (BJCB) and operated as a supporting agency of the Combined Communications Board in Washington, based in London. Following the end of the war it became the British Joint Communications-Electronics Board, and the Wireless Telegraphy Board was disbanded. The interests of users of radio other than Government departments were represented by the Post Office.

The Wireless Telegraphy Act 1949 vested responsibility and the necessary statutory powers with respect to regulating the use radio frequencies in the Postmaster-General. In 1968, in preparation for the change of status of the Post Office, the PO Engineering Department brought together in one unit engineers who were responsible for the numerous technical aspects of radio regulatory work. This unit then transferred to the new Ministry of Posts and Telecommunications in 1969.

When the Ministry was abolished in 1974, responsibility for radio regulation passed to the Home Office in a newly created Radio Regulatory Department. The Department was divided into eight technical branches: broadcasting services; radio interference; regulatory and monitoring; common services; land mobile; space services; microwave and maritime; and long range planning.

The Department moved to the Department of Trade and Industry in 1983, seen as a logical move given the Ministry's responsibility for telecommunications, information technology and innovation. The Department was re-titled the Radio Regulatory Division (RRD).

A further change of name occurred in 1986 when the Radio Regulatory Division became the Radiocommunications Division. Finally, the Division became the Radiocommunications Agency in 1990, under the Government's Next Steps programme.

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.

1921

The first Rural Automatic Exchange (RAX) in this country was brought into service on 24 October at Ramsey, Huntingdonshire, in the Peterborough Telephone Area. It was a 40-line exchange, supplied by Siemens.

This was the first in a series of trials of exchange equipment intended to improve the telephone service to rural subscribers. Rural areas were until now served by small manual exchanges attended by caretaker operators. Exchanges with fewer than 20 subscribers did not normally give service at night or on Sundays, an obvious inconvenience. The Post Office eventually standardised on a GEC designed 100-line automatic exchange for rural areas known as RAX No. 5 in 1929.

A larger GEC design with 200 lines known as RAX No. 6 was introduced in 1931 and yet larger units with more facilities were adopted in 1937. These larger exchanges were suitable for both rural and urban areas and had facilities for dialling into, and receiving calls from main exchanges. Because the unit concept of construction was adopted, which allowed the exchange to be enlarged by the addition of further cabinets of equipment, they were known as UAX (Unit Automatic Exchange) Nos. 12, 13 and 14. The Post Office was now able to give rural communities a telephone service as good as that provided to urban subscribers.

Kiosk No. 1 was introduced, the first standard Post Office design and primarily intended for use as an open-air public call office in rural areas, later superseded by the No. 3. It was similar in design to the old wooden-box call offices, but was made up from three sections of reinforced concrete and fitted with a wooden door with the two sides and front containing glass panels. Once the kiosk had been constructed it could then be painted any colour to meet local conditions. The most distinctive feature of this kiosk was the spear-like finial on the roof, and roof signs were added on certain obscure kiosks. An initial contract had been placed with Somerville & Company in March 1920 for the supply of 50 kiosks at a price of £35 each - this was reduced to £15 in following years because of demand. Although the kiosk was quite successful, it was considered that a better design could be found. Eventually by 1931 the installation of the No. 1 in rural areas was discontinued.

Toll Exchange was opened at 3-5 Norwich Street, Fetter Lane, London, on 17 September, inaugurating the Toll System of call routing in London. The system was necessary because of heavy demands on the Trunk Exchange in GPO South in Carter Lane, EC4 (opened in 1904). As part of the new system, 350 direct short-distance trunk lines were diverted from GPO South to the new Toll Exchange by means of a new cable scheme, a major operation causing severe disruption in Ludgate Hill, and between the Old Bailey and Ludgate Circus. London subscribers saw a greatly improved service. Previously, making a trunk call involved what was known as 'delay working' where a subscriber booked long distance calls in advance and was later rung back by the operator when one of the trunk lines became available. Obviously, the greater the demand made on the exchange, the longer the wait. Under the new 'Toll' system subscribers were now able to ask the local operator for 'Tol' for calls to exchanges within the London Toll Area. They were then connected to the Toll operator who completed the call while the subscriber remained at the telephone. Later, as more automatic exchanges were introduced, the subscriber simply had to dial 'TOL' to be connected to the Toll operator.

The London Toll Area boundary was extended in 1923 and again in 1928, so that eventually Southampton, Portsmouth, Reading, Bedford, Colchester and the whole of Kent and Sussex were included. The system was later introduced to other large cities and remained in use until the late 1950s when, with the advent of STD, Toll was eventually phased out.

The Post Office Advisory Council was set up this year to advise the Postmaster-General and keep the Post Office in touch with the views of the business community and other users of its many services. Its membership consisted of representatives of a variety of interests in careful balance - political, national, social and functional.

The Research Section of the Post Office Engineering Department was moved from the City to a number of army huts at Dollis Hill. The Dollis Hill Research Station was later built on the same site in 1933.

1922

The first 'relay' automatic exchange for the public telephone service in this country was provided for the Post Office at Fleetwood, Lancashire by the Relay Automatic Company (originally set up as the Betulander Automatic Telephone Company by Marconi's Wireless Telegraph Co Ltd in 1913). It was opened for service on 15 July.

The relay system was developed from that devised by Gotthief Angarius Betulander, an engineer in the Swedish Post Office and, as the name 'relay' suggests, was dependent on electro magnetic relays for performing the switching function. There was thus no frictional wear and the system was an entirely different concept from electro-mechanical type such as Strowger which involved the moving of a brush on a wiper over a number of contacts. In principle, the relay system, with its use of markers and relay crosspoint matrix and link trunking, foreshadowed the later crossbar and reed-electronic exchanges (although the crossbar switch itself had already been invented).

However, it was the Strowger system which was finally adopted by the Post Office (see below), and the relay system was considered better suited for small Private Automatic Branch Exchanges (PABXs). The first installed for the Post Office was brought into service at Debenhams in Wigmore Street, London, on 8 December 1923. After a series of full scale experiments in which different automatic telephone systems had been tried (including the Lorimer system in Hereford, Strowger system in Leeds, Western Electric rotary system at Darlington, Siemens system at Grimsby, and the relay system at Fleetwood), the Post Office decided to adopt the Strowger system as its standard. By the spring of 1924, Britain had nearly 265,000 lines working on 23 automatic exchanges, from a capacity of 25 line to 15,000, and by seven different manufacturers. Strowger exchanges became the backbone of the UK telephone network and remained a key component for over 50 years. The last Strowger exchange, Crawford in Scotland, was not removed from service until 23 June 1995.

It had been thought that there might be difficulties using the Strowger system in very large cities such as London where numbers of large exchanges, and consequently a great number of inter-exchange calls, created a highly complex interconnected network. A number of solutions were put forward, but the problem was solved when the Automatic Telephone Manufacturing Co Ltd of Liverpool, working in conjunction with the Post Office, developed the 'Director'. This was a Strowger system with a number storage and translation facility which could 'direct' telephone calls through the complex network of circuits linking exchanges in large cities. This was achieved by the translation of the digits dialled by a calling subscriber to other numbers in order to direct the call over the most convenient route to the required exchange. The Director system also included the facility for calls to be dialled from automatic to manual exchanges where the required numbers appeared visually before the operator handling the incoming call, who then completed the connection manually. This Coded-Call Indicator (CCI) facility meant that a subscriber connected to a London automatic exchange dialling the number of a subscriber on a London manual exchange would be unaware that the call was not completed automatically. In addition, there would be no change of procedure for the subscriber once the manual exchange had been converted to automatic working. This was an important advantage, as the transition from manual to complete automatic working would not be concluded for very many years.

One feature of the decision to adopt the Strowger system was the many thorough economic planning studies made by the Post Office to determine the conditions justifying the adoption of automatic working. These studies demonstrated the need to be able to extend an exchange over a ten-year period and hence the requirements for uniformity of design, constructional and circuit practices. Another essential feature was pooling of patents amongst the British manufacturers of automatic exchange equipment to standardise all Strowger equipment construction. This co-operation between the Post Office and the manufacturers led to the first Bulk Supply Agreement the following year.

The telephone system in Southern Ireland was transferred to the Eireann Administration (then the Irish Free State); 194 telephone exchanges with 19,037 lines and 553 call offices passed into the control of the new administration.

The first automatic exchange in Hull was opened in Queen's Road.

A telephone service was established with the Netherlands (Holland) on 15 August.

The first trials with teleprinters were staged.

Experimental transmitters were not uncommon at this time and in this year the Marconi Wireless Telegraph Company began public broadcasting.

1923

The first of the series of so-called 'Bulk Supply Agreements' between manufacturers and the Post Office was signed in this year, the first being the Telephone Exchange Equipment Bulk Supply Agreement (TEEBSA) for the supply of automatic exchange equipment. It was signed between the Post Office and the four manufacturers (Automatic Telephone Manufacturing Co, General Electric Co Ltd, Siemens Brothers Ltd and Standard Telephone & Cables). It marked the beginning of the progressive development and standardisation of the British telephone system over the next 40 years following the adoption of the Strowger system of step-by-step working using two motion selectors in 1922). There were clear advantages for all parties to the agreement: manufacturers avoided having to tender for all exchanges, parallel development work was unnecessary, manufacturers all had a 'fair' share of available Post Office business, and advantageous prices were negotiated for the Post Office. The Agreement was renewed a number of times and a fifth manufacturer, Ericsson Telephones Ltd, became a party to it in 1927.

The establishment of the British Telephone Technical Development Committee in 1933 contributed to effective standardisation of the system. Throughout the 1950s and 1960s, however, there was a progressive abandonment of the TEEBSA and other bulk supply agreements in favour of competitive tendering. The TEEBSA was eventually terminated in October 1969 when competition for the supply of step-by-step equipment was introduced. Other bulk supply agreements with manufacturers concerned the following:

  • Loading Coils, 1931-1963
  • Cable, 1931-1963
  • Batteries, 1931-1953
  • Telephone Subscribers Apparatus, 1933-1968
  • Transmission (Audio and Voice Frequency Telegraph)
  • Equipment, 1936-1946
  • Cordage and Cords, 1936-1952

A licence was granted to the States of Jersey to operate a local telephone service: 15 exchanges with 1,639 lines and 26 call offices were transferred to the States Department of the island at a cost of £32,000.

Communication across the Atlantic by wireless telegraphy was established for two hours on 14 January. Speech passed from Rocky Point, Long Island, to the Western Electric Company's factory at New Southgate, North London.

The British Broadcasting Company (BBC) was set up by Western Electric, Marconi, General Electric, British Thomson-Houston, Radio Communication and Metropolitan Vickers. It received its licence for regular broadcasting of programmes of speech and music, and opened stations in London, Birmingham, Manchester and Newcastle-upon-Tyne.

The minimum fee from London call offices was reduced from 3d to 2d in July.

1924

Following the development of the beam system (short wave point-to-point radio telegraphy), the Marconi Wireless Telegraph Company entered into an agreement with the British Government in November for the provision of stations to set up an Imperial Wireless Chain in England, Australia, Canada, India and South Africa.

The first Siemens No. 16 automatic Non-Director exchange was opened at Swansea. It was based on the step-by-step system and was also used later at Edinburgh, Sheffield, Brighton and Leicester exchanges. It was similar in design to what had become the standard automatic system in 1922, and many of its features were reproduced in the design of standard circuits.

Telephone No. 150 was introduced. Similar to earlier telephones in that it was a candlestick model, it was innovatory in introducing the dial to most subscribers for the first time. Reflecting the progress of automatic switching, the dial operated the automatic exchange switching mechanism by sending out a series of electrical impulses corresponding to the number being dialled. It was no longer necessary for the operator to connect all calls. Where a No. 150 was still connected to a manual exchange, the space in the base of the telephone for the dial was covered by a dummy insert (used as a number label holder) which could be replaced by a dial when the exchange went automatic.

A competition to design a new kiosk was organised and several leading architects were invited to submit designs. Models were placed on view behind the National Gallery and selection was made by the Fine Arts Commission. The winner was a design by Sir Giles Gilbert Scott and, after a slight modification to the door and change of material from mild steel to cast iron, it was adopted by the Post Office and designated Kiosk No. 2, or K2.

Some important improvements to the door mechanism and window arrangement were contained in the kiosk. The glass was deliberately made into small panels so that breakages could be repaired with a minimum of renewal. There was also a ventilation system which worked through perforations in the dome. Because of its cast iron construction it weighed approximately 1.5 tons and had more interior space than its predecessor. The most distinctive feature was undoubtedly the bright red colour scheme. The kiosk's introduction in 1927 was mainly confined to London and some large provincial towns and proved to be very successful. It was eventually made obsolete in June 1936, although a number continue to be found in London today and very few in other large cities. A number have been designated as Grade II listed buildings and will continue to be preserved.

Gilbert Scott's original model of what was to become the K2 still stands outside the National Gallery, at first glance identical to its progeny although it is in fact different in some details, principally in its wooden construction.

1925

As a result of economic planning studies to determine the conditions justifying the adoption of automatic working the Engineer-in-Chief laid down the following criteria for automatic working:

  • the average subscriber's calling rate should not be less than five calls per day
  • not less than 4,000 calls per day should need to be switched automatically
  • not more than 40 per cent of the originating calls must involve manual handling.


The Electrophone exchange was closed on 30 June. The Electrophone service had been transmitted over the telephone network of the National Telephone Company, and later that of the Post Office, by the Electrophone Co. Ltd. from the 1890s. Effectively what would today be regarded as a cable company, the Company folded after the closure of the Electrophone Exchange, which followed the decline of the service in the face of competition from the increasingly accessible and varied programmes of the BBC radio service.

A new type of coin-box was introduced, the well-known Button A and Button B prepayment equipment, and for over 25 years its design remained unchanged despite various developments in the design of kiosks. It was usually installed in both automatic and central battery manual exchange areas. To make a call in automatic areas, users inserted the appropriate fee which prepared the circuit for dialling. In manual areas, callers were connected to the operator on insertion of the call fee and, in both cases, the caller then depressed Button A. This allowed the coins to be deposited into the cash box and the call to be transmitted. If a call could not be connected for some reason, or if there was no reply, Button B was depressed, the line was disconnected for five to seven seconds and all the coins were returned to the caller.

Although 6d (2p) and 1/- (5p) slots were available for other calls, the minimum fee necessary to make a local call at the time was 2d. The mechanism was originally designed to check the presence of two pennies by a weighing operation. It was set to a minimum and maximum acceptable weight for the coins as a safety margin, but as the fee was gradually increased to 3d and then 4d the safety margin became smaller and eventually unacceptable. A mechanical counter was considered too expensive as the modifications needed would have been too many and too complex. To overcome this problem a new mechanism was devised by Hall Telephone Accessories Ltd and was in effect a combination of the two basic methods: three pennies were checked by weight and the mechanism waited for the insertion of the fourth penny before allowing the call. The system required the smallest amount of additional equipment and could be easily fitted. A limitation was that it could not be easily adapted for an increase beyond 4d.

In 1959 the first versions of the new Pay-on-Answer payphones were being introduced and at the end of the 1950s began to supersede the 'Button A and B' models. This was made necessary following the introduction of Subscriber Trunk Dialling (STD) in major towns which allowed no reasonable modification to enable the 'A and B' box to be used to pay for automatically connected trunk calls. However, some 'A and Bs' remained in active use in Scotland until 1992. The primary reason for their retention lay in their remote locations. Because the boxes functioned on a single-channel radio link there was no reasonable solution for many years that would allow the use of Subscriber Private Metering (the principle on which the latest pre-payment payphones operated).

The London to Glasgow trunk telephone cable with repeaters was completed to form the backbone of the British trunk network.

Large multichange exchange areas were developed between now and 1927. Satellite exchanges were built to radiate around a main exchange to serve the centre and environs of a large provincial city, using a linked numbering scheme. Early examples were established during this time at Leeds, Edinburgh and Sheffield.

Western Electric's interests outside the USA were taken over by International Telephone Corporation (ITT). As a result Western Electric Limited in England was renamed Standard Telephones & Cables Limited.

1925-1927
beam wireless telegraph service was established with Montreal, Melbourne, Cape Town and Bombay.

1926

The Post Office long-wave wireless station at Hillmorton, near Rugby with worldwide range, was brought into service on 1 January, known as Rugby Radio Station. The station used a huge water-cooled transmitter (call sign GBR), dissipating 10kW and using 54 thermionic valves on a wave length of 18,750 metres. Initially, it commenced transmission in Morse code on 16kHz with an aerial power of 350kW. At the time it was the world's most powerful transmitter using thermionic valves. Later in the same year two-way conversation by radio telephone was also established for the first time between England and the USA from Rugby.

A continuous telephone service was established with Germany by through circuit.

J L Baird (1888-1946) demonstrated television before the Royal Institution on 27 January.

1925-1927
beam wireless telegraph service was established with Montreal, Melbourne, Cape Town and Bombay.

1927

The British Broadcasting Company became the British Broadcasting Corporation on 1 January.

A regular public transatlantic telephone service from London to New York using long-wave radio transmission on a wavelength of 5,000 metres (60kHz) was begun on 7 January at 1.45 pm. The original tariff was £15 for three minutes, reduced to £9 the following year.

The first director exchange in Europe was opened at 270 High Holborn and was known as Holborn Tandem. It provided a switching centre for exchanges in the Director Area which were not in direct communication. (The director technique allowed the Strowger automatic system to be used in large cities, using a three letter exchange code in front of the number, and was introduced in 1922.)

Cast iron kiosks were introduced (Kiosk No. 2), designed by Sir Giles Gilbert Scott. The installation of this kiosk was confined to London (where many can be seen today) and some large provincial towns following a competition held in 1924.

The No. 4 kiosk was introduced. It was first proposed in 1923 and a prototype was erected in Bath in 1926. In addition to the telephone it contained facilities for buying stamps and posting letters. The standard No. 4 kiosk was designed by the Post Office Engineering Department on the basis of the successful No. 2 and received final approval in 1927. It was constructed in cast iron and was considerably larger than any of the other types. Painted vermilion outside and a flame colour inside, it gained the nickname of 'The Vermilion Giant'. Only 50 of these kiosks were ever made, at an original cost of £50 6s 9d each. They were intended to be a miniature Post Office, located where no such facilities existed or where expense prevented a sub-post office from being built. Unfortunately these kiosks were unsuccessful. Many people complained about the noise of the stamp machine while they were using the telephone, and the rolls of stamps in the machine tended to become soggy in damp weather. For these reasons, and because of the high unit cost, the Post Office decided in 1935 that no further kiosks of this type would be installed.

The London Toll system was divided between Toll 'A' and Toll 'B' exchanges because of the increase in Toll traffic which made it necessary to divide the direction of originated traffic. Toll 'A' manual exchange opened on 3 December on the 5th Floor, GPO South, Carter Lane, EC4 to handle traffic outwards. The old exchange at Fetter Lane, opened in 1921, became known as Toll 'B' and handled traffic into London .

An international time signal was broadcast throughout the world from Rugby Radio Station. A joint development with the Admiralty and Board of Trade, it was intended to assist mariners. The time signals were generated from the Royal Greenwich Observatory.

In 1949 quartz clocks provided by the Post Office replaced the mechanical pendulum clocks in the Greenwich Time Signal (GTS) generating apparatus at the Royal Observatory. These clocks continued in use until 1967, when caesium atomic standards were introduced.

Rugby still transmits the Greenwich Time Signal, which is derived from the National Physical Laboratory's atomic resonance standard. The laboratory is now the UK's national centre for time - its atomic clocks generate the UK's time standard, which is made available via transmissions from Rugby Radio Station. The BBC's "pips" are derived in part from the same signal (the BBC has been responsible for generating the 'pips' since 5 February 1990 when it assumed the role from the Royal Greenwich Observatory).

Telephone service was established with Austria, Denmark, Norway and Sweden.

1928

The first automatic exchange in the City of London was opened at Bishopsgate.

An experimental wireless transmission of still pictures was carried out by the BBC on 30 October.

The Post Office standard non-director exchange system was introduced. This meant that the Post Office had now standardised on the basis of two forms of equipment: non-director for use in provincial areas and director for use in exchanges in large cities (see 1924 entry). On non-director exchanges the proportion of out-going traffic compared with that of director exchanges was comparatively small. Therefore, the general principle of backward holding (the bridge being located in the final selector) was adopted on non-director systems, whilst forward holding (from the first selector) was used on director exchanges.

Creed's Teleprinter No. 3 was adopted as the standard inland telegraph instrument.

Telephone service was established with Czechoslovakia, Gibraltar, Hungary, Italy, Luxembourg, Mexico, Portugal and Spain.

1929

The New York Wall Street stock market crashed - an event probably stimulated and speeded by the use of the telephone for the panic selling of shares.

The development of the immersed electrode principle in transmitter design made it possible for the Post Office to introduce two new innovative telephone designs (Teles 162 and 232). These were the first instruments to successfully incorporate a 'hand combination' (a handset with combined receiver and transmitter) which could be used with central battery lines. Provision was made in the circuit to reduce sidetone. The new designs were also revolutionary in their use of plastics, being among the first large-scale production items to be produced in 'Bakelite', and there was now a choice of colours.

The first standardisation rural automatic exchange was opened at Haynes near Bedford on 4 February, a 100-line unit (No. 5) (see 1921 entry).

Cable & Wireless Ltd was registered on 1 April, formed as a result of an Imperial Telegraph Conference of 1928. Previously UK telegraph services with places outside Europe were conducted by telegraph companies, with the exception of wireless circuits with the Commonwealth and two Anglo-Canadian cables, which were worked by the Post Office. However, as the Post Office long-distance wireless services were generally cheaper than the cable services, the telegraph companies were threatening to dispose of the cable system. For strategic reasons it was felt necessary to retain the cables under British control and the solution settled upon by the Conference was to merge the British wireless and cable interests. Accordingly, the Post Office was required to hand over the 'beam' wireless stations and the two Anglo-Canadian cables to the new company on a 25-year lease. The company was to operate on semi-public utility lines and was to be controlled by the Imperial Communications Advisory Committee (see following entry).

The Imperial Communications Advisory Committee was constituted to advise the Government on technical questions, and international and Commonwealth issues. It comprised representatives of the defence services, the Post Office and the Commonwealth, and was chaired by a cabinet minister. In 1944 it was renamed the Commonwealth Communications Council and became the Commonwealth Telecommunications Board in 1949.

Kiosk No. 3 was introduced, again designed by Sir Giles Gilbert Scott. This kiosk was intended for sites of special architectural importance, scenic localities and for general outdoor use in rural and urban areas. In August 1930 it was decided to adopt the No. 3 as standard for rural areas once the stock of No. 1's had been exhausted. The actual design was very similar to the No. 2 kiosk but was made largely from concrete instead of cast iron. Only the window frames were painted red, with the rest of the kiosk being painted a stony grey colour. Because concrete was a rather poor material for telephone box construction this was the last standard box to employ its use.

A new building at Rugby Radio Station to house the shortwave transmitter ("A" Building) was opened.

A telephone service was opened between the Isle of Man and the mainland on 28 June.

personal call service was introduced throughout the British inland trunk and toll telephone service on 1 August.

'Metropolitan', 'National' and 'Empire' automatic telephone exchanges were opened in Wood Street, Cheapside, London on 31 August.

An audioconferencing 'conference communication' system composed of transmitters and loudspeakers was used on 23 October to connect audiences in Manchester, Liverpool, Birmingham, Glasgow, Leeds, Newcastle, Cardiff, Southampton and Portsmouth with the Institution of Electrical Engineers in London.

On Monday 2 December, 22 experimental police telephone boxes, installed as part of a new scheme for policing were made available for general use in the Barnes, Kew and Richmond District of 'V' Division, Metropolitan Police District.

The BBC extended its services to include broadcasts of television.

1930

A picture telegraph (facsimile) service between the Central Telegraph Office and Berlin was opened on 7 January. Services to other European cities soon followed.

On-demand trunk service was introduced based on a new transmission and routing plan in which zones were divided into groups. The principal exchange in each group, the Group Centre, had operational control of originating traffic for all dependent exchanges in the group.

A radio-telephone service was opened with Australia on 30 April. The service was extended to South Africa and Argentina later in the year.

Automatic metering up to 3d (just over 1p) was introduced on director exchanges.

A motor cycle telegraph messages service was inaugurated at Bournemouth.

The Manchester Director Area was opened, encompassing the Ardwick, Collyhurst and Moss Side exchanges.

Advice of duration and charge (ADC) at callers' request was introduced.

Control of Toll traffic in London was devolved upon local auto-manual switchboards.

1931

The first voice-frequency telegraph system with 12 carrier channels was installed between London and Dundee. By means of voice-frequency dialling, operators at zone centres were able to dial directly to subscribers in distant zone centres, thereby avoiding the cost and delay involved with incoming operators.

The first 200-line unit automatic exchange (No. 6) was opened.

The page-printing teleprinter (the Teleprinter 7B) was introduced by Creed.

The Birmingham Director Area was opened encompassing the Harborne, Northern and Victoria exchanges.

A telephone cable was laid to the Channel Islands.

Telephone service was established with New Zealand.

An engineering complaint and repair service was made directly available to director subscribers by dialling 'ENG' and to some non- director subscribers by dialling '97'.

'Micro-Ray' (microwave) communication was first demonstrated by STC between Dover and Calais.

1932

The International Telecommunications Union (the oldest of the intergovernmental organisations which form the specialised agencies of the United Nations) was created from the International Telegraph Union and the International Radiotelegraph Union.

The Bridgeman Committee was set up under the chairmanship of Lord Bridgeman to investigate criticisms that the Post Office, as a large-scale commercial undertaking, should be run along the lines of a business concern rather than as an ordinary government department. This criticism had culminated in a submission to the Prime Minister of a memorial signed by 320 Members of Parliament asking for an enquiry into the status and organisation of the Post Office with a view to effecting any necessary changes in its constitution.

The Bridgeman Committee's report, published in the same year, found no change to be necessary to the existing Parliamentary control, but drew attention to defects in the organisation.

The original structure of the Post Office telephone service was modelled on that of the National Telephone Company. Thus, on the commercial side the local operational unit was the Surveyor's District of which there were 13, excluding London. The Surveyor was responsible for the postal, telegraph and telephone services: on the telephone side he was assisted by District Managers who, in conjunction with Head Postmasters, were responsible for the provision and the quality of the telephone service in their districts. Responsibility for the telegraph service was divided between the Surveyor's Office and the Head Postmasters.

However, none of these officials had any control over the engineering aspects of the telephone and telegraph services. The engineering field was the responsibility of totally separate Superintending Engineers Districts, each under the control of a Superintending Engineer who had a number of Sectional Engineers working to him. The organisation was further confused by the fact that neither the District Managers' and the Sectional Engineers' Districts, nor those of the Surveyors and the Superintending Engineers were conterminous. Moreover, the engineering and non-engineering sides were each responsible to separate headquarters in London: the Superintending Engineer to the Engineer-in-Chief and the Surveyor to the Secretary's Office. This centralisation of authority in London prevented real local responsibility, and the separate rigid hierarchies prejudiced effective co-ordination of operational and engineering effort.

A departmental committee under the chairmanship of Sir Thomas Gardiner was then appointed with the aim of promoting efficiency in Post Office organisation and to deal with the application of the substantially increased decentralisation recommended by the Bridgeman Committee.

The Gardiner Committee's recommendations, published in its report of 1936, led to the setting up of eight regions in the provinces, each in the charge of a Regional Director responsible for the control and co-ordination of all Post Office services within his region. Additional to these eight provincial regions, two further regions were set up in London - one for Posts and one for Telecommunications. The provincial regions were divided into Head Postmasters' districts for the management of the postal and the telegraph services (in practice these were already in existence).

The telephone service regions were divided into telephone Areas under Telephone Managers, of which there were ultimately 57 for the provinces and nine in London. Telephone Managers, with Head Postmasters acting as their agents on certain matters, were to be responsible for the day-to-day control of all aspects of the telephone service (engineering, traffic, sales and accounts). They were also to be accountable to the Regional Director for the overall efficiency of the telephone service in their territory. The first two regions (Scotland and North East) were set up in 1936, followed by the two London regions (Telecoms and Postal), and the changes throughout the country were in place by 1940.

With this large degree of devolution to the regions, there was now a need for central co-ordination and an overall scrutiny of Regional performance, as ultimate responsibility still remained with the Headquarters Administration. To deal with posts, telecommunications, buildings and staff pay, five committees were constituted when the earliest Regions were set up. These were:-

Standing Postal Estimate Committee (SPEC)

Standing Telecommunications Advisory Committee (STAC)

Standing Factories Advisory Committee (SFAC)

Clerical Estimates Committee (CEC)

Standing Motor Transport Advisory Committee (SMTAC), which was set up the previous year in 1935.

The task of these committees was to scrutinise annual estimates, compare actual with estimated expenditure, and to study performance statistics. The committees were composed of representatives from relevant departments and each committee included representatives of the Accountant General's Department.

The Post Office introduced the Telex Printergram service. The 'Telex' Exchange, opened on 15 August, enabled teleprinters to be used on telephone subscribers' lines for intercommunication and for transmission of telegrams to the Central Telegram Office. Teleprinters 7B were used.

The first ultra-short-wave radio telephone link, used as part of the inland telephone network, was set up across the Bristol Channel, over a distance of 13 miles.

The first submarine cable for carrier working was laid from Britain to La Panne in Belgium. It contained 120 wires arranged as four-wire circuits and provided 90 telephone circuits using 1+2 carrier equipment.

The Post Office introduced trunk service on demand, relieving telephone users of the need to book trunk calls in advance.

The Post Office introduced telephones with anti-sidetone induction coil. The anti-sidetone telephone circuit had been invented in 1920.

The first British experiments in carrier telephony were carried out using the London-Derby cable.

The first large centralised Directory Enquiry Bureau was opened in August.

Telephone service was established with Canada (direct), South Africa and the USSR.

Sleeve-control switchboards were introduced. These permitted any position and any cord circuit to be used to handle any type of trunk circuit.

A standard switchboard was introduced for police telephone and signal systems.

The first 'Strowger' type non-director exchange with a remote manual board was opened at Horsforth.

1933

Imperial Chemical Industries Ltd. discovered polyethylene, or polythene as it became known. This material, because of its low dielectric constant, became widely used for submarine cable insulation in place of gutta-percha and rubber, and for many other purposes in telecommunications.

Telephone service was opened with India, Northern and Southern Rhodesia and Turkey.

Phonogram work was transferred from telephone to telegraph staff.

'Demand' trunk service was extended to group centres.

The first nine-channel (bothway) voice frequency telegraph system (using a four-wire telephone circuit) was brought into service. This system provided automatic calling clearing and supervisory conditions over long-distance circuits.

The British Telephone Technical Development Committee (BTTDC) was set up to co-ordinate development work between the Post Office and the five manufacturers party to the Telephone Exchange Equipment Bulk Supply Agreement. These manufacturers - ATE, Associated Electrical Industries, Ericsson Telephones, GEC and STC - were represented on the Bulk Contracts Committee which allocated telephone exchange business on an equal share by value basis. Before the creation of the BTTDC each manufacturer had individually carried out their own design and development for Post Office contracts. As a result of the setting up of the BTTDC all development work for the Post Office was shared between the five parties and all information produced for the Post Office was to be known to all parties. The aim was to standardise equipment design and obviate parallel development. The Post Office and its five exchange equipment suppliers were now able to coordinate further development and promote a high degree of standardisation of circuitry and components, particularly of relays and selectors.

A separate exchange for international calls was opened at Faraday Building in Queen Victoria Street, London. It had 121 sleeve-control positions equipped for 480 circuits. Known as the 'switchboard of the world', cable and wireless telephone channels radiated from Faraday across the globe. The later use of high-frequency radio circuits, which involved rather different operating techniques, required the opening of a specialised exchange in Wood Street.

1934

H S Black, an American, formulated the principle of negative feedback, revolutionising the design of telephone repeaters.

On 1 October, the Post Office introduced cheap night rates - 1s (5p) maximum - for trunk telephone calls as part of the Kingsley Wood (the then Postmaster-General) plan for advertising and popularising the telephone.

The transferred-charge service was first introduced on the inland telephone system in this year. This enabled callers to have a call made through an operator charged to the person receiving that call.

Kiosk No. 5 - the K5 - was introduced. It was a transportable kiosk made of steel-faced plywood, which could be assembled and dismantled, for use at exhibitions and other temporary locations. It is not known how many were made, and none appear to have survived to the present day.

Short-range radiotelephone service with coastal ships was opened via the Seaforth Radio coast station.

The first 800-line Unit Automatic Exchange (UAX 7) was introduced.

The first ultra-short-wave radio telephone link (London-Belfast) was opened.

The first commercial use of a microwave radio link was introduced, between Lymne in Kent and St Inglevert in France, 35 miles apart.

1935

Automatic metering up to four units (4d) was introduced on Unit Automatic Exchanges, on the UAX 12 and later on the UAX 13 and 14 types.

The first standardised UAX 12 (100-line unit) was introduced.

1+2 carrier transmission was introduced.

The first telegraph four-channel bothway voice-frequency system using a two-wire telephone circuit was introduced.

Teleprinter ancillary working was introduced.

The first telephone multi-channel working (three channels per open-wire circuit) was introduced.

1936

The speaking clock was introduced, a service at first available only in London at Holborn Exchange. The Post Office had held a competition to decide on the voice to be recorded, and subscribers dialling TIM would hear the 'golden voice' of Miss Jane Cain, a London telephone operator, giving the Greenwich time correct to one-tenth of a second.

The accuracy of the speaking clock was calibrated and corrected by referencing to a time signal from the Royal Greenwich Observatory which was broadcast by Rugby Radio Station.

The voice of Jane Cain was replaced by that of Pat Simmons in 1963.

Kiosk No. 6 - the K6 - was introduced to commemorate the Silver Jubilee of the coronation of King George V. The 'Jubilee Kiosk', as it became known, was once again designed by Sir Giles Gilbert Scott and was similar in appearance to Kiosk No. 2, the main difference being that the vertical bars in the windows and door were spaced further apart to improve visibility. The K2 had not penetrated far outside London, but the 'Jubilee' model became the first genuinely standard kiosk and was installed all over the country.

Under the "Jubilee Concession", introduced as part of that year's celebrations, kiosks were to be provided in every town or village with a post office, regardless of cost. As a result of this scheme over 8,000 new kiosks were installed, adding impetus to the spread of the K6.

In the following year, the "Tercentenary Concession" was introduced: if a local authority committed to paying £4 a year, then the normal subscription, for five years then the Post Office would install a kiosk on request almost anywhere. This scheme remained in force until 1949, and led to almost another 1,000 K6s being introduced. The "Rural Allocation Scheme" was introduced to replace it: kiosks were allocated to rural areas and installed where recommended by a rural local authority, whether likely to prove profitable or not.

The 'Jubilee Kiosk' is perhaps the best remembered example of Gilbert Scott's work (with the possible exception of Liverpool Cathedral) and is to this day fondly regarded as a typical British landmark. K6s survived the introduction of Nos. 7 and 8, but during the 1980s and early 1990s were frequently replaced with the modern KX 100 - 400 series of payphone booths. Thousands of old K6 kiosks were sold off at public auctions. Some were scrapped, but many more were put to a variety of imaginative and bizarre uses in private hands. However, the Department of the Environment and English Heritage worked with BT to identify kiosks, including more than 1,000 K6s, worthy of listing as being of special architectural and historical interest, mainly near existing listed buildings or in attractive town and country locations.

BT's approach had now almost gone full circle: instead of replacing them, the policy came to be to retain and reintroduce K6 kiosks in situ whenever practical, even if not listed. In 1999 there were over 15,000 of these old style kiosks in heritage sites, and the K6 kiosk was by now a registered design of British Telecommunications plc. From November 1997, BT licensed K6 kiosks for use by competitors.

In 1999, BT operated a network of over 140,000 public payphones of various designs across the UK, compared to 81,000 ten years previously, with an average of 5,000 new units being installed each year.

The 'Pip' tone signal was provided on timed calls as a regular feature for the first time from 15 August.

The world's first 12-channel carrier cable for commercial traffic was laid between Plymouth and Bristol.

The world's first coaxial cable was laid by the Post Office between London and Birmingham, providing 40 channels for telephone traffic.

The London Telecommunications Region and eight provincial regions were set up as a result of the findings of the Bridgeman Committee.

An ultra-short-wave link was established with the Channel Islands.

The first nine-channel short-wave radio link was installed between Belfast and Stranraer in Scotland.

Call queuing, with cyclic distribution, was introduced at larger directory enquiry bureaux.

A limited Anglo-Continental telex service was introduced.

'Country Satellite' exchanges were introduced for remote localities where there were no more than ten subscribers.

Trials were held of two-frequency trunk telephone signalling and dialling.

EMI developed a method of television transmission over screened pair cables and produced equipment which gave successful transmission of 405-line television over 15 miles of cable. This was used for the broadcast of the coronation of George VI in May 1937.

Telephone No. 332 was introduced by the Post Office, an improved design on the revolutionary No. 162 (introduced in 1929) as it was less liable to breakage and provided extra facilities controlled by press buttons.

1937

The 999 emergency telephone service was made available to London subscribers from 30 June and was later extended throughout the country. When 999 was dialled a buzzer sounded in the exchange and a red light flashed to draw an operator's immediate attention.

This was very far removed from the sophisticated information service designed by BT and launched on 6 October 1998. The new information service allowed details of both the calling number and the address from which a 999 call had been made to be transferred automatically to the emergency authority operator's screen.

A pair of submarine coaxial telephone cables was laid between Great Britain and Holland carrying 16 circuits (a four channel system and a 12-channel system).

The first 12-channel carrier telephone system on special carrier cable was opened between Bristol and Plymouth.

The first standardised 200-line Unit Automatic Exchange (No. 13) was opened.

Glasgow Director Area was inaugurated with the opening of Halfway Exchange.

The London Trunk Director Exchange was opened.

The world's first underground cable for television was laid by the Post Office between Alexandra Palace in North London, Broadcasting House in Portland Place, and other central London locations.

1938

The London to Birmingham coaxial cable was brought into use, initially carrying 40 circuits with wideband working.

A H Reeves, an Englishman (1902-1971), invented Pulse Code Modulation, a revolutionary new system of telephonic transmission.

The first standardised 800-line Unit Automatic Exchange (UAX No. 14) was opened.

The first Administrative Telegraph and Telephone and Radio Conference of the new International Telecommunications Union was held in Cairo.

1939

The outbreak of war on 3 September 1939 heralded six years of hugely increased activity and demand for the Post Office, placing great strain on its resources. An almost immediate effect was the sharp drop in available staff as over 73,000 men and women from the Post Office joined the armed forces within the first few weeks of the war - 15 per cent of the total staff. In some areas the loss was even more keenly felt; 25 per cent of Post Office engineers joined up in 1939, and a substantial percentage of Post Office technical research and telecommunications operating staff were absorbed into signals units of the Forces.

Some preparations prior to September 1939 had already been made when war seemed likely. Additional cables had been laid between important towns over different and alternative routes, particularly vulnerable sites had been by-passed, and old manual telephone exchanges when superseded by automatic exchanges were not dismantled, but held in reserve. In addition, public trunk lines were earmarked for future use of the Services, and these were promptly switched over in September 1939.

During the first six months of the war, before heavy German bombing started, the Post Office made use of the opportunity to complete the link up by telephone and telegraph of Home Defences, particularly Fighter and Anti-Aircraft Commands. By the time of the Battle of Britain, as the Headquarters of Fighter Command, at Bently Priory near Stanmore, Middlesex, was a communications centre in touch with all defence stations and information sources across the country via Post Office facilities. From here the Commander-in-Chief was able to observe the broad 'air picture' and co-ordinate his Fighter Groups. In addition to the vast telephone communications network provided by the Post Office for raid reporting, a complex teleprinter network was also installed. With the collapse of France and when invasion seemed a real possibility, new aerodromes, battery sites, searchlight centres and radar stations had to be set up - and all needed linking with telephone communications, again carried out by Post Office engineers.

Later in the war, as part of the preparations for the Normandy invasion, a new network of cables, switchboards, telephones and teleprinters had to be set up along England's south coast to control the D-Day build up. Once the invasion was under-way, new cross-channel cables were laid and by VE-Day the Post Office had made direct communication possible by telephone or teleprinter to all Allied Forces in North West Europe.

On the home front the Post Office had soon organised itself to meet the demands of the war. ARP services were set up in all departments, and a Home Guard Force of over 50,000 was raised to defend Post Office telegraph and telephone systems in the event of invasion. Other Post Office Defence Forces included medical staff, fire fighters and first aiders, all of whom were particularly called upon during the bombing raids of the early war years. During this time Post Office engineers battled to repair bomb damage to plant and cables, yet were still able to open the additional military channels of communication described above.

The contribution of the Post Office, particularly on the telecommunications side, was significant enough to earn the praise of General Eisenhower, Supreme Commander of Allied Forces in Europe. Although under great strain, the Post Office met the challenges demanded of it, largely through the efforts and sacrifices of its staff. Of the 73,000 men and women who left the Post Office to join up, 3,800 gave their lives. On the Home Front, a further 413 Post Office employees died whilst carrying out their responsibilities.

'Two frequency' inland trunk signalling and dialling was introduced. This beginning of trunk mechanisation allowed operators to dial distant subscribers without the assistance of a second operator.

Teleprinter working was introduced on the Anglo-Continental telegraph cables.

The first mobile Unit Automatic Exchange was put into service.

International telephone services were suspended on 30 August (with a few exceptions) and not restored until 23 June 1945 with the reopening of the service to the USA, Canada, and Kenya.

The Defence Teleprinter Network was opened on the outbreak of war.

1940

The Private Manual Branch Exchange Switchboard (PMBX)1A was introduced.

The London-Birmingham coaxial cable was extended to Manchester.

On 29 December 1940 the CTO was set on fire by burning debris blown in from adjacent buildings in one of the most destructive German air attacks of the Second World War. A reserve telegraph instrument room had been established in the basement of King Edward Building nearby and, in the longer term, telegraph services were maintained by transferring work to the outskirts of London. The interior of the building was completely destroyed. Its damaged upper floors were unsafe and had to be dismantled. The shell of the ground and first floors was refurbished - the ground floor for office accommodation, and the first for instrument rooms. The new telegraph equipment was opened for service in June 1943.

1941

The telephone 12-channel carrier system was standardised.

The Liverpool DirectorArea was inaugurated with the opening of Advance Exchange.

The Telegraph Zone Centre Decentralisation Scheme was inaugurated.

1942

Shared service was introduced on automatic exchanges.

The transfer of the London Toll 'A' lines to automatic working and the opening of the new manual board took place on 14 November.

A VHF radio multi-channel telephone link was converted to frequency modulation for the first time.

1943

Subscriber dialling in London Director Area was extended.

The first submerged repeater was laid between Anglesey and the Isle of Man in a submarine coaxial cable using a rigid housing.

What is generally regarded as the world's first programmable electronic computer (Colossus) was designed and constructed by a Post Office Research Branch team headed by T H Flowers (1905-1998). It was constructed at Dollis Hill where it was first demonstrated on 8 December 1943. It was transported and rebuilt at Bletchley Park near Milton Keynes, the centre of British wartime code breaking operations, in January 1944.

The purpose of Colossus was to decipher German non-Morse encrypted communications - known as "Fish" at Bletchley - which were transmitted at high speeds on a teleprinter machine, called the Lorenz SZ, using the Baudot 32 letter alphabet. The mathematician Bill Tute had broken the German teleprinter codes in 1941, but it was recognised that the decryption process could be largely automated to reduce the time taken to decipher the messages. Flowers was consulted by Max Newman (later Professor of Mathematics at Manchester) who was responsible for the automation process. Flowers had been involved with work at Bletchley since the previous year, when the mathematician Alan Turing and fellow cryptanalysts had sought technical assistance from the Post Office in the breaking of Enigma.

Flowers' great contribution was the recognition that an electronic signal could be used to replicate the code pattern generated by the Lorenz machine, which could then be read by optical sensors in a code breaking device. He proposed using valves instead of the mechanical switching units employed in an earlier device. His proposal was not taken seriously at first, since valves were thought to be too unreliable and fragile, but Flowers knew from his pre-war research into electronic telephone systems that valves were reliable if they were not moved or switched off.

It is now recognised that without the contribution of the code breaking activity, in which Colossus played a major part, the war may have lasted considerably longer. It was in the preparations for D Day that Colossus proved most valuable, since it was able to track in detail communications between Hitler and his field commanders.

By D Day itself a Colossus Mk II had been built. Flowers had been told that it had to be ready by June 1944 or it would not be of any use. He was not told the reason for the deadline, but realising that it was significant he ensured that the new version was ready for 1 June, five days before D-Day. In fact, there were 11 machines by the end of the War, all but one of which were destroyed on Churchill's orders, the last being moved to GCHQ at Cheltenham where it apparently remained in use until at least 1958 and possibly into the 1960s. A working replica of Colossus has been constructed in recent years and housed at Bletchley Park.

The original Colossus consisted of 1,500 valves (the Mark II used 2,400 valves) and was the size of a small room, weighing around a ton. Described by Flowers as a "string and sealing wax affair", it nevertheless could do in hours what otherwise could have taken weeks, being able to process 5,000 characters a second to run through the many millions of possible settings for the code wheels on the German enciphered teleprinter system. Designed as a code breaking machine, and without an effective memory or a stored program, it was not quite what is regarded as a computer today. Nevertheless, it predated other contenders for the title of the first modern working computer, and was the forerunner of later digital computers.

In March the long wave building ("C" Building) at Rugby Radio Station was severely damaged by fire. A newly built counterpart to GBR was able to take traffic within a few days. The damage to the building and GBR was repaired within six months.

1944

The Imperial Communications Advisory Committee, constituted in 1929, was renamed the Commonwealth Communications Council. It became the Commonwealth Telecommunications Board in 1949.

1944 - 1948

The inland teleprinter manual switching was introduced.

1945

Arthur C Clarke, an English expert on space research and later to become renowned for his science fiction classic '2001: A Space Odyssey', suggested in 'Wireless World' the use of synchronous satellites for communications, the first occasion such a concept was proposed.

A direct Anglo-German polythene coaxial submarine cable was laid.

The CS Alert (No. 2) was sunk with all hands in February off the North Goodwins, probably by a submarine. In April the CS Monarch (No. 3) was sunk by a mine off Orford Ness, Suffolk.

The German cableship 'Nordeney' was given to the Post Office as a replacement for war losses and was renamed the Alert, the third of that name. She was scrapped in 1960.

Some continental telephone and telegraph and transatlantic telephone servi

1946

Continental and overseas telephone services continued to be gradually reopened.

A submerged repeater was inserted into the Anglo-German cable.

Cabinets and pillars were introduced for subscribers' local cable schemes.

CS Monarch (No. 4) was built - at the time the largest cable laying and repair vessel in the world, capable of remaining at sea for more than three months without refuelling or entering port. Her most notable achievement was the laying of the first Transatlantic Telephone Cable (TAT 1) in 1956. She remained in service for 24 years and was sold to Cable & Wireless in 1970, thereafter sailing under the name 'Sentinel'.

The Post Office Central Training School was moved from Dollis Hill in North London to a site near Stone, Staffordshire.

1947

An Anglo-Dutch polythene coaxial cable was laid.

Cable & Wireless Ltd. was nationalised on 1 January by the Treasury's purchase of the company's shares, and by the Post Office's acquisition of the company's telecommunications assets in Britain (with the exception of its telegraph cables and terminal station at Porthcurno), including the return of the wireless stations previously leased to the company in 1929.

From that date Cable & Wireless operated no telecommunications services in the UK until 1982, and conducted its overseas business as an independent entity entirely separate from the Post Office. In many ways, nationalisation did not dramatically affect the way the company operated. Successive Governments left it largely to its own devices, though with strict limits on its ability to spend and expand. Government control of its day-to-day affairs was limited to Treasury oversight of its investment plans and the appointment from time to time of Post Official officials to the company's board of directors. From 1974 the company was allowed rather more commercial freedom, so long as it agreed to consult with the Government over any major programmes which might be politically or financially sensitive.

With the election of a new Conservative Government in 1979, committed to the withdrawal of state intervention in industry and the free market philosophy, a new approach was inevitable. In July 1980 Sir Keith Joseph, Secretary of State for Industry, outlined plans for privatising Cable & Wireless in his policy statement which announced the Government's plans for restructuring the Post Office and liberalising the telecommunications market. In November 1981, following the passing of the British Telecommunications Act which created British Telecom as a public corporation separate from the Post Office, Cable & Wireless was privatised with the sale of 50 per cent of its shares. There were further sales of Government shares in November 1983 and December 1985.

In 1981, Cable & Wireless was a member of the consortium which set up Mercury Communications Ltd., which was to be British Telecom's only competitor in the UK until the ending of the so-called "duopoly" in the provision of telecommunications services in 1991. Mercury subsequently became involved in setting Cable & Wireless Communications with Nynex, Bellcable Media and Videotron.

1948

The Bell Telephone Laboratories, USA, announced the invention of the transistor.

The International Teleprinter Alphabet No. 2 was adopted for the inland telegraph service.

shared service was made obligatory for all new residential applicants and for removing residence subscribers.

Telephone service was opened with China.

The phototelegraph service with Europe was re-introduced for the first time since the beginning of the war.

1949

The radio-telephone service with ships in the Thames Estuary was introduced.

The Tercentenary Scheme for the provision of telephone kiosks was abolished. The Rural Allocation Scheme was introduced: kiosks were allocated to rural areas and installed where recommended by a rural local authority, whether likely to prove profitable or not.

A London-Birmingham television radio relay link was opened using large tube coaxial television cables.

Phonogram automatic distribution equipment was installed at Newcastle-Upon-Tyne.

The Commonwealth Communications Council, founded in 1929, was reconstituted as the Commonwealth Telecommunications Board with essentially the same terms of reference.

1950

A long-distance television cable was brought into service between London and Sutton Coldfield, the first of its kind.

The Edinburgh Director Area was inaugurated with the opening of Central and Fountainbridge Exchanges.

The control of the overseas services of Cable & Wireless Ltd from the United Kingdom was transferred to the Post Office. At the same time, the radio beam stations leased to Cable & Wireless were returned to the Post Office.

Field trials of the pressurisation of trunk and junction cables radiating from Leatherhead were held.

The success of the Strowger system to meet network demands - largely as a result of the arrangements under the Telephone Exchange Equipment Bulk Supply Agreement (signed in 1923) and the British Telephone Technical Development Committee (set up in 1933) - led to an important decision. There had been rapid advances in electronic techniques during and immediately following the Second World War which led the Post Office and their exchange equipment manufacturers to believe that electronic exchanges could be developed within a short space of time without pursuing alternative electro-mechanical systems. As a result, the decision was now taken to work towards a progressive change of the network from mechanical Strowger systems to electronic systems. This policy was jointly adopted and led in due course to a Joint Electronic Research Agreement (JERA) and the formation of the Joint Electronic Research Committee (JERC) in 1956. These initiatives were put in place to examine various possible solutions for electronic exchanges, and to avoid unnecessary duplication of research and development by sharing such work amongst the five manufacturers party to the Bulk Supply Agreement with the Post Office.

The hope was that the intermediate step of the introduction of register controlled crossbar systems, apparent in other telecommunications administrations elsewhere, would not be necessary under this policy. In the event, development of electronic systems proved more difficult than originally thought, and by 1957 the Automatic Telephone and Electric Company realised that to maintain their position in the export market they needed a viable crossbar system to market. As a result the company developed in time the 5005 Crossbar System. Original development of electronic systems was based on time-division- multiplex techniques and a prototype TDM exchange was built and installed in the Post Office Research Station at Dollis Hill. Parties to JERC co-operated in designing and building a large electronic exchange of the same type which was put into service by the Post Office at Highgate Wood in 1963. The experience of Highgate Wood showed that TDM techniques were uneconomic and difficult to achieve with the technology and components then available. The parallel space division approach, using reed relays for switching, proved more promising and development was concentrated in this area, leading eventually to the successful TXE2 and later the TXE4 systems.

Four submerged repeaters were fitted in tandem to a cross-channel cable.

The first phase of the Teleprinter Automatic Switching Scheme was introduced.

An Anglo-Danish submarine coaxial cable was laid.

Private Automatic Branch Exchanges Nos. 1 and 2 were introduced.

1951

Telephone Act became law in August which enabled the Postmaster-General to set rental charges and so forth by statutory regulation. The passing of the Act was the first recognition in law of the telephone as a separate instrument from the telegraph. It was also the first Telephone Act passed by Parliament, 75 years after the invention of the telephone.

Until this time the Postmaster-General conducted the telephone service under powers conferred by a number of Telegraph Acts, because of the court decision in 1880 that a telephone was a form of telegraph under the telegraph acts then in force.

The objective of the legislation was to simplify the provision of a telephone service by replacing the existing system of individual contracts between customers and the Postmaster-General for providing apparatus and equipment with a system of Statutory Regulations.

Post Office engineers evolved an entirely new type of deep sea telephone cable. Known as the lightweight submarine cable it had a steel strand in the centre instead of the conventional layer of steel armour wires on the outside. This lightweight type of cable was both cheaper and easier to lay.

A television coaxial cable was brought into use between Birmingham and Manchester.

The Swiss made "Ipsophone"a record / answer machine, became the first such device to be available in the UK. As an "approved attachment" they were not supplied by the Post Office, but by the Ansafone Company. The Post Office did not market its own machine until 1958.

1952

The Post Office External Telecommunication Executive was formed to control the overseas services transferred from Cable & Wireless. This department later became the International Division in 1979, and British Telecom International (BTI) in 1981. BTI operated until the Project Sovereign re-organisation in 1991, when its functions were split between various new divisions.

A new telex network was opened for Government departments only.

1953

Agreements were signed on 1 December between the British Post Office, the American Telephone & Telegraph Company, the Canadian Overseas Telecommunications Corporation and the Eastern Telephone & Telegraph Company for the provision of a transatlantic telephone cable.

Pressurisation of trunk and junction cables was introduced.

1954

A new Directory Enquiry Service - which included the use of the London Postal Area printed street directory - came into operation in January.

new public inland telex service was established using a separate network integrated with international telex circuits.

An Anglo-Norwegian submarine telephone cable was laid between Aberdeen and Bergen. At the time it was the longest submarine cable in the world at a length of 300 nautical miles and was laid by the Post Office cableship HMTS 'Monarch' (No. 4).

The Teleprinter Automatic Switching Scheme was introduced.

A step was taken towards full automatic working with the gradual introduction of through-operator dialling, which permitted an originating controlling operator to set up calls automatically over two or more links to a terminating automatic exchange through switching equipment at zone centre exchanges. This stage began with the opening in 1954-1955 of two large automatic trunk exchanges, followed by similar exchanges in other important centres.

1955

The first cordless switchboard was opened at Thanet Exchange.

The last Post Office inland morse telegraph circuit was recovered from between Barra and South Uist in the Outer Hebrides.

1956

The first transatlantic telephone cable was laid between Oban in Scotland and Clarenville in Newfoundland, a distance of 2,240 miles. After crossing Newfoundland, a further submarine cable was used to complete the connection to the mainland of North America, some of the circuits terminating in Canada and some in the USA. The Post Office cableship HMTS 'Monarch' (No. 4) participated in the lay. The cable entered service on 25 September at 6pm. It was withdrawn in 1978.

The Weather Forecast Service and the Test Match Information Service were introduced.

The Joint Electronic Research Committee (JERC) was formed to co- ordinate research and development on electronic charges.

1957

The Road Weather Information Service was introduced.

The free call allowance for residential subscribers was abolished.

1958

The Subscriber Trunk Dialling (STD) service, whereby telephone callers are able to make trunk calls automatically without the aid of the operator, was introduced into the United Kingdom by the Queen dialling a call on 5 December from Bristol Central Telephone Exchange to the Lord Provost of Edinburgh, over 300 miles away - the greatest distance over which a subscriber trunk call could be made at the time. Afterwards, the Queen operated a switch which put 18,000 telephones connected to Bristol Central onto the new system.

Before STD, Bristol subscribers could dial direct to 2,600 stations connected to 41 local exchanges outside the city. Afterwards they could dial calls to 427 exchanges, including most of those in London, Birmingham, Manchester and Edinburgh. Before STD could be introduced, however, telephone charges, designed for manual operation, had to be simplified. Only then could full automation follow. The introduction of Group Charging Areas reduced as well as simplified the cost of most trunk calls. For instance, the call made by the Queen to Edinburgh lasted 2 minutes 5 seconds and cost 10d (4p); under the old charging system the call would have cost 3s 9d (19p).

The first automatic telex exchanges were opened at Shoreditch in London and at Leeds.

The Teletourist Information Service was introduced in London; in English (24 hours) and in French and German (7 pm-11 pm).

Nineteen countries established the European Conference of Postal and Telecommunications Administration (CEPT), expanding to 26 during its first 10 years. Another 17 countries from Eastern European joined these in 1992 so that CEPT henceforward covered almost the whole of Europe.

Original members were the former monopoly holding telecommunications administrations which handled operational and regulatory functions. Up until the early eighties the CEPT dealt mainly with administrative, technical and operational tasks, but sovereign and regulatory functions gradually grew in importance. From September 1992 the CEPT was a body of the newly established National Regulatory Authorities (NRAs), and dealt exclusively with sovereign / regulatory matters. Operators established their own organisation called ETNO (European public Telecommunications Network Operators' association), based in Brussels, to deal with technical and operational tasks previously covered by CEPT.

The Post Office introduced Answering Machine No. 1; an answer only machine which gave out a 20 second message, played twice to ensure callers from payphones received the whole message. A second model,

Answering Machine No. 2, followed in 1963.

1959

The 700 series of telephone designs was introduced by the Post Office. It was much lighter than previous designs with lightweight components and a new easily cleaned plastic material, available in a range of six attractive colours, marking the demise of black as the standard telephone colour. The familiar 'curly cord' connecting the handset to the telephone now also made its first appearance. The 700 series was designed for the Post Office by W.J. Avery of Ericsson, but owed a distinct debt to the Bell 500.

The Postmaster-General, Ernest Marples, announced the new Friendly Telephone policy at a press conference in the House of Commons on 11 March. The new policy was result of a report entitled, Telephone Service and the Customer on a visit by a Post Office team the previous November to study the telephone system in the United States.

Anticipating the greater role that would be played by automation in the system, the policy was intended to ensure that customers received a friendly service when personal contact was made. A striking feature of the policy was that "subscribers" were henceforward to be known as "customers", and that operators in particular were to be released from the strict rules which governed what phrases they were allowed to use when speaking to customers. It was noted at the time that for the previous 54 years operators had not been allowed to say "Good Morning" when taking a call, only such formal phrases as "Number, please".

As part of the policy, social surveys were conducted to discover what customers wanted, and an organisation set up to develop facilities to meet their need as far as possible.

The policy was promoted within the Post Office with signed copies of booklets outlining the new approach being sent to everyone in the telephone service. The booklet stated, "The aim and purpose of the telephone service is not only to serve, but to please the customer. Everything must be subordinated and surrendered to that aim. Our telephone service must be a personal service to meet the customers' wishes. We must study their wishes all the time; we must then satisfy them by a service which is courteous, pleasing and speedy."

The Postmaster-General tape-recorded a personal message to all operators, to which they could listen by ringing a special number. In the Areas, Telephone Managers held local press conferences, and posters were put up in exchanges.

In its objectives and its customer focus, there are remarkable similarities with BT's Putting Customers First programme which followed over 40 years later.

The first versions of Pay-On-Answer coinboxes on public payphones were introduced and began to supersede the Button A and B models . They were necessary following the introduction of STD in major towns because the A and B boxes could not be modified to cope with automatically connected trunk calls. Public demand had been for a coinbox slot that would accept the 3d piece, but after only seven years the box was modified to accept 6d (2 1/2p) and 1s (5p) coins only. The introduction of decimal coinage in 1971 made another modification necessary. Thereafter, there was only one further modification before Pay-On-Answer payphones were phased out. Plans were made in 1978 to update the entire payphone system by exploiting the advantages of electronic technology. It was decided that the new system would be based on the pre-payment approach with a refund of unused coins where appropriate. Modernisation began in 1985 when BT embarked on a £160 million programme to replace red phoneboxes and Pay-On-Answer mechanisms with the newly introduced blue payphone in new housings, the KX 100 - 400 family of anodised aluminium and stainless steel booths.

New dialling codes, preliminary to the start of subscriber trunk dialling in London, were introduced in the London Director Area on 6 April.

"0 for Operator", which had been introduced to London in 1928 when the first automatic director exchange was opened in London, TRU for Trunks and TOL for Toll were replaced by 100.

The second transatlantic telephone cable (TAT 2) was laid by the Post Office cableship HMTS Monarch (No. 4) between Penmarch, France and Sydney Mines, Nova Scotia, Canada via Terrenceville, Newfoundland, Canada.

TAT 2 was taken out of service in 1982 after 23 years of service.

car radiophone service for vehicle users was introduced in South Lancashire on 28 October.

The Freephone service was made available to subscribers in any part of the country.

1960

The conversion of the Inland Telex Service to automatic working was completed.

credit card service for inland and overseas telephone calls was introduced on 1 March (see also 1988 entry).

The CS 'Alert' (No. 4) was launched on 8 November.

The new engaged tone was introduced at Bristol to conform to international standards.

The first London STD exchange (Watford) was opened.

The cable pressurisation scheme was extended to include local cables from exchanges to cross-connection cabinets.

The first direct cable link between the United Kingdom and Sweden was laid.

Telephone No. 706 was introduced.

The Post Office introduced a "Freephone" service for business users, a forerunner of the BT Freefone and Lo-call services.

1961

The Anglo-Canadian cable (CANTAT 1) was laid by the Post Office cableship HMTS 'Monarch' (No. 4) between White Bay, Newfoundland, Canada and Oban, Scotland, as the first section of the submarine telephone cable network linking the Commonwealth. This was the first time that the lightweight submarine cable, developed by the Post Office in 1951, was used in service.

CANTAT 1 was taken out of service in 1982 after 23 years of service.

The first STD exchanges in the City of London (Metropolitan, London Wall, Moorgate) and Central London (Victoria, Tate Gallery, Abbey) were opened.

recipe telephone information service was opened in Birmingham.

radio telephone service from aircraft was introduced.

1962

The Post Office Satellite Communications Station at Goonhilly Downs in Cornwall began working. The station was designed to track communication satellites and through them to transmit and receive telephone, telegraph and television signals. The station used a British-designed dish-type aerial which was the first of its type.

Dish-type aerials were later adopted throughout the world for satellite communications. The station took part in the first transatlantic television transmission made via an artificial satellite - Telstar. The first broadband active communications satellite, Telstar was launched into orbit from Cape Canaveral on 10 July. It circled the earth once every 158 minutes at a height of between 600 and 3,500 miles. The day after it was launched, Telstar was used to transmit the first high-definition television pictures across the Atlantic.

The first telephone cable from the United Kingdom to the Faroe Islands and Iceland was opened (SCOTICE).

The first experimental PAM/TDM electronic exchange was opened at Highgate Wood, London, in December.

Kiosk No. 7 - (the K7) - was put on trial in January in London. A design in aluminium by the architect Neville Comber, it met with initial approval from members of the public, but failed to withstand the rigours of British weather. Only five aluminium examples entered service, four in London and one in Coventry. A further half dozen were commissioned in cast iron, but it is not known where they were erected, if anywhere. The aluminium prototypes continued in service for the next twenty years.

1963

International Subscriber Trunk Dialling (ISD) was introduced on 8 March, allowing London subscribers to dial Paris numbers.

The Commonwealth trans-Pacific cable (COMPAC) was laid between Canada and Australia. The PO cableship HMTS 'Monarch' (No. 4) participated in the lay.

The third transatlantic telephone cable (TAT 3) was opened between Tuckerton, New Jersey, United States and Widemouth Bay, Britain. It was taken out of service in 1986 after 23 years of service.

Operator dialling on telephone circuits between Britain and the United States was introduced.

New clocks using a revolving magnetic drum replaced the original speaking clock introduced in 1936. The 79 separate phrases required for a 12-hour clock were recorded as circular tracks spaced 1/16 inch apart along the length of the drum. The pips were not recorded on the drum but were derived from an oscillator. The Speaking Clock had accuracy to approximately 1/20 second. Like the first clock, the second speaking clock had its accuracy calibrated and corrected by referencing to a time signal from the Royal Greenwich Observatory, broadcast by Rugby Radio Station.

A competition to find a replacement for Miss Jane Cain's voice  for the Speaking Clock was won by Miss Pat Simmons, a supervisor in a London telephone exchange. She was to be heard until Mr Brian Cobby replaced her.

The new cordless international telex switchboard was opened at Fleet Exchange, London.

The Post Office introduced Answering Machine No 2. Like its predecessor it was an answer only model, but with a longer message facility (of up to three minutes), this second version was more suited for use on information lines. Its first use was in Birmingham, for a "Dial-a-Prayer" service. The first Post Office / British Telecom supplied answering / recording machine was not nationally available until 1981.

1964

Datel services were introduced, enabling data to be transmitted over private telegraph circuits and the telex network. The following year, Datel service were extended to enable data to be sent over private telephone circuits and the public telephone network. Datel services subsequently became available to a number of European countries and the United States.

The first automatic crossbar exchange (TXK1) in the United Kingdom was opened at Broughton in Lancashire.

The first Small Automatic Exchange (SAX) was opened at Bury in the Brighton Telephone Area.

Trial Pulse Code Modulation (PCM) systems were introduced on junction cables.

The Post Office was a founder member of INTELSAT; the International Telecommunications Satellite Organisation founded to develop a global commercial satellite communications system.

Originally having a membership of eleven, there were over 100 member countries in 1999, the UK being the second largest shareholder. BT was the UK representative on INTELSAT. On the technical side, BT contributed substantially to studies on the characteristics and utilisation of successive generations of INTELSAT satellites.

1965

INTELSAT 1 (Early Bird) the first commercial communications satellite, was launched into a synchronous orbit of 22,300 miles on 6 April.

Prime Minister Harold Wilson MP opened the BT Tower (then known as the Post Office Tower) on Friday 8 October in London, Britain's highest building at the time at 620 feet (189 metres), including a 40 ft (12 metre) lattice aerial on top. It was designed to carry aerials for the Post Office microwave network covering some 130 stations throughout the country, including the Post Office satellite earth station at Goonhilly.

The Tower - the focal point for this network - and the four-storey building below are equipped to handle 150,000 simultaneous telephone connections and to provide 40 channels for black and white or colour television. It was partly to meet the growing demands of broadcasting that the Tower was opened, enabling the use of microwaves instead of landlines.

Postmaster-General Anthony Wedgwood Benn, opened the Tower to the public on 19 May the following year, accompanied by Sir Billy Butlin who had taken the lease on the revolving restaurant on the 34th floor.

Begun in 1961, the Tower cost £9 million to build, and weighs 13,000 tons, including 95 tons of high tensile steel in the base and 695 tons of mild steel in the structure. It was designed to sway not more than 20 centimetres (almost 8 inches) each way in winds up to 100 mph. There are 4,500 square metres (50,000) square feet) of glass on the outside, set in stainless steel window frames.

The Tower Suite conference area, 158 metres (520 feet) above ground, revolves two and a half times each hour. Nylon tyred wheels running on inner and outer circular rails support the rotating structure which weighs 30 tons.

During the first year the Tower was open to the public - from 19 May 1966 to 19 May 1967 - it was visited by nearly 1 million visitors, 105,000 of whom dined in the revolving restaurant. They were transported by the Tower's two lifts, which are among the fastest in Europe, travelling at 6 metres per second. During that first year the lifts between them travelled nearly 70,000 kilometres. The fare for everyone, whether dining or not, was 4 shillings (20p) and half price for children.

The country was shocked when a bomb placed by a terrorist bomber on the 31st floor of the Tower exploded at 4.30am on 31 October 1971. A warning had been phoned to Purley exchange at 9pm the previous evening, but despite a search nothing had been found, and the call had been thought to be a hoax. The result of the bombing was a tightening of security that left the Tower largely closed to the public on a permanent basis. The total number of visitors to the Tower up until that time had been 4,632,822, making it one of London's most popular tourist attractions. The restaurant remained in operation until 1980 when its lease expired, when it was also closed to the public except for hospitality events or charity fund-raising functions, such as Comic Relief.

Trial installations of electronic equipment for telephone exchanges with a capacity for up to 200 telephone lines were brought into service at Leamington Spa on 25 March and Peterborough on 10 June. Leamington Spa was a GEC "RS31" design, Peterborough was an Ericsson Telephones Ltd. "Pentex" design. Both were forerunners of the Post Office TXE2.

The public radiophone service for vehicle users in South Lancashire  was extended to the London area.

Datel services were extended.

The TAT 4 transatlantic telephone cable was laid between Tuckerton, New Jersey and St. Hilaire-de-Riez, France. It was retired in 1987 after 22 years of service.

The first Internet was begun by Bolt, Beranek & Newman (BBN). Called the ARPANET, it was a network connecting the University of California at Los Angeles (UCLA), SRI in Stanford, USA, University of California at Santa Barbara and the University of Utah, using 50Kbps circuits. It was completed to its original specification in 1969.

In 1984 ARPANET was divided into two networks, one to serve the military (MILNET) and the other to support academic research (ARPANET). The US Department of Defense continued to support both networks.

In 1992 the Internet Society was chartered, triggering the World Wide Web phenomenon.

1966

All Figure Numbering (AFN) was introduced - starting in the Director Areas (London, Birmingham, Edinburgh, Glasgow, Liverpool and Manchester). AFN had become essential with the development of direct international dialling as the mixed letter and number combinations were insufficient to meet the needs of expanding service.

Telephone No. 712 - later No 722 - (the 'Trimphone') was made generally available.

This innovative design by STC, half the weight of the more traditional 700-type telephone, originated in 1961 when the Post Office decided it needed a luxury telephone to add to its range. Towards the end of 1963 the Post Office settled on the design by STC, and in 1964 placed a contract for 10,000 units. The first example of the Trimphone was presented in May 1965 by the Postmaster-General, Anthony Wedgwood Benn, to a newly wed couple in Hampstead in a ceremony marking the installation of the ten millionth telephone to be installed in Britain. The new design was trialled in the London North West Telephone Area in the same year, before becoming available throughout the country in 1966 in three two tone colour combinations. By 1980 there were 1.6 million in operation out of a total telephone population at that time of 27 million.

The Trimphone was an entirely new and lightweight design, which among its novel features incorporated the receiver and microphone in the earpiece as a composite unit. The user spoke into the handset in the normal manner, but the sound was carried up inside the handset to the microphone. Because the handset was hollow, as opposed to the solid mouldings of earlier phones, this was the first telephone with the feature of which most modern phone users are now wary. If the user attempted to place a hand over the microphone in order to make a confidential aside, the sound was still transmitted inside the handset with embarrassing results.

Another feature was a tone call device in place of the conventional bell, which had a volume control to suit the preference of the subscriber. A transistorised oscillator connected to a miniature loudspeaker produced the warbling tone.

However, possibly the most striking out of many new features was the luminescent dial, which glowed green in the dark. This effect came from a small glass tube of tritium gas, which gave off beta radiation and made the dial fluoresce. Although the radioactivity was equivalent only to that given off by a wristwatch, with people less likely to have as close or continuous contact as a timepiece, it was later felt wise to withdraw this facility as public concern over radioactivity grew. By 1981, towards the end of the general availability of the Trimphone, a keypad version was marketed. BT later invested in a widely publicised initiative to safely recover and dispose of Trimphones from customers' premises.

The first fully operational production electronic telephone exchange in Europe (the first small-to-medium sized one in the world) was opened at Ambergate, Derbyshire. This was a TXE2 reed relay exchange.

The TXE2 was a result of research into space division electronic exchanges  and its introduction was part of the major programme of investment into the network by the Post Office using modern switching equipment which began around this time. Initially, the TXE2 was used for exchanges with a capacity of up to around 2,000 lines. The Plessey 5005 (TXK1) crossbar exchange, also produced under agreement by GEC, was used for larger installations in non-director areas and group switching centre exchanges. The BXB (TXK3) crossbar exchange, a derivative of the ITT Pentaconta crossbar system developed in France, was made by STC for larger installations in director area and trunk-transit exchanges.

The TXE4 electronic exchange, a development complementing the TXE2, was introduced from 1976 to take over from crossbar the provision of large exchanges.

During the 1980s and 1990s the TXE and TXK families of electronic and electromechanical exchanges were gradually replaced with System X and System Y digital exchanges in a £20 billion investment programme. The last TXE2 exchanges (Ballycastle, Northern Ireland, Llandovery, Wales and Ramsbury, England) were closed on 23 June 1995. The last TXK crossbar exchange, at Droitwich, was withdrawn in 1994.

The UK network became totally digital on 11 March 1998 with the closure of the last electronic TXE4 exchanges at Leigh-on-Sea and Selby and their conversion to System Y (AXE 10) and System X respectively.

The first Dial-a-Disc service was opened in Leeds.

1967

The final section of SEACOM (the South East Asia Commonwealth cable) was opened, linking Australia, Hong Kong and Singapore.

The first London Pulse Code Modulation (PCM) cable route was opened between Sunbury-on-Thames and Faraday Exchange, London on 27 November. PCM allowed up to 24 telephone conversations to be carried over two wires.

A prototype Confravision studio was opened in London.

The Overseas Telegraph Services new automatic relay centre was opened.

'Lincompex', a new type of radio telephony terminal equipment, was introduced on several overseas routes.

1968

The Post Office installed the world's first PCM (Pulse Code Modulation) exchange at the Empress telephone exchange near Earl's Court in London. Postmaster-General John Stonehouse opened the exchange on 11 September with an inaugural call to the Mayor of Hammersmith.

The possibilities of PCM systems for the transmission of speech had been originally developed more than 30 years earlier in 1937 by A H Reeves working in Paris for the Western Electric Company, and PCM was first patented by him in France the following year. He proposed a transmission system in which voice signals were electronically coded into strings of digital pulses, transmitted in this form, and then turned back into speech at the receiving end. His ideas were well in advance of his time, but the technique could not be economically realised until suitable components, particularly transistors, were available.

Technical advances in the early 1960s enabled the possibility for the first time of PCM providing an economic solution to the problem of providing multi-channel systems designed for speech networks. Conventional analogue transmission allowed two pairs of wires to carry two conversations at one time. PCM transmission increased this to 24 simultaneous conversations by interleaving the groups of pulses corresponding to different callers (Time Division Multiplexing), reducing the need for many new cables. PCM transmission also allowed a greater diversity of telecommunications services in addition to telephony, including facsimile and data transmission.

The particular significance of Empress was that it was the first of its type in the world to switch PCM signals from one group of lines to another in digital form. PCM transmission had been introduced the previous year on selected routes, but switching on non-direct routes was done by conventional electromechanical means. This meant that digitally transmitted calls had to be converted to analogue for switching, then converted back to digital form for transmission over the next PCM route. The Empress Exchange was the result of Post Office research into overcoming this inefficient and expensive problem. Empress also demonstrated that an integrated PCM transmission and switching system was capable of working fully within the existing network of electro-mechanical (Strowger and Crossbar) systems. This first use of computer-like technology with micro-electronic circuits was part of the investment programme of the time and led directly to the System X family of digital switching systems and the totally digital service and integrated digital network which BT now operates.

Kiosk No. 8  - (the K8) - was introduced in July. Two designers, Douglas Scott and Bruce Martin, had been commissioned in 1965 to produce designs for a new kiosk. The designs had to incorporate the best features of previous designs and be suitable for both urban and rural surroundings. Bruce Martin's design was eventually selected and when introduced had been produced in just over one year, the shortest time then taken to create a new kiosk. It was made from cast iron and contained full length toughened glass, and became the successor to Kiosk No. 6  -(the K6) - for all replacements and new installations as the standard payphone housing.

The first all-transistor 12 MHz (2,700 circuits) coaxial cable was brought into use.