The Plessey Company plc was a British-based international electronics, defence and telecommunications company. It originated in 1917, growing and diversifying into electronics. It expanded after the second world war by acquisition of companies and formed overseas companies. In 1989 it was taken over by a consortium formed by GEC and Siemens which broke up the Plessey group. Only a few organisations now remain with the Plessey name.

Early history

The Plessey company was founded in 1917 in Marylebone, central London. The original shareholders were Thomas Hurst Hodgson, C.H. Whitaker, Raymond Parker and his brother Plessey Parker. A talented German engineer, William Oscar Heyne was employed by the company. Heyne later became the Managing Director and Chairman of Plessey and was one of the key figures in the development of Plessey during the 1920s and 30s. The company moved to Cottenham Road in Ilford early in 1919 (and then to Vicarage Lane where it remained). In 1925 the original company was wound up and a new one formed with a greater share capital. Most of the early work carried out by the company was mechanical engineering rather than electronics.

The Clark connection

An early customer of Plessey was a galvanising company called British Electro Chemists. One of that company's shareholders was Byron G. Clark, an American, who was also a business associate of T.H. Hodgson, one of the founders of Plessey. The Clark family would eventually dominate the management of Plessey for most of its history. Byron's son Allen George Clark joined the company in 1921, and went on to become a major driving force behind the development of Plessey, followed later by his sons John Allen Clark, and Michael William Clark, both of whom rose to prominent positions in the company.

Electrical manufacturing

During the 1920s Plessey began to diversify into electrical manufacturing, important contracts included the manufacture of early radios for Marconi and the production of telephones for the GPO. Because of the increased production, Plessey moved to Vicarage Lane Ilford in 1923. In 1929 the television pioneer John Logie Baird had his first production televisions produced by Plessey. The company also produced the first British made portable battery radio in the same year.

The manufacture of electrical components also became a key area of growth for Plessey, a vast array of different components was manufactured by the company, many under licence from overseas companies. Plessey became one of the largest manufacturers in this field as the radio and television industries grew. In 1936/7 turnover was more than £1 million and Plessey became a public company on 17 March 1937.

Aircraft components

Aircraft components was another market into which Plessey diversified. In 1936 Plessey obtained a number of important manufacturing licences from American companies such as, Breeze Corporation for aircraft multi-pin electrical connectors, Federal Laboratories for Coffman starters (an explosive cartridge device used to start aircraft engines), and Pump Engineering Services Corporation for the manufacture of Pesco fuel pumps. Plessey went on to produce large numbers of Pesco fuel pumps for Rolls Royce Merlin engines, and in 1940 the fuel pump for Britain's first jet engine was also supplied by Plessey.


During the war, Plessey produced a vast array of components and equipment for the war effort, including shell cases, aircraft parts, and radio equipment such as the R1155 (receiver), and T1154 (transmitter). In all 161,500 electronic equipments were produced.

To allow greater production, Plessey converted 5 miles of twin tunnel, built for a new extension to the London Underground Central Line from Leytonstone to Newbury Park, into a factory. The company also built a new factory at Swindon, and opened several other shadow factories around the country producing munitions. Caswell became the first dedicated research centre in 1940. The wartime workforce of Plessey grew to over 10,000 people.

Later history

At the end of the war the company's orders dropped from £5 million in 1944/5 to only £263,000 in 1946. The workforce fell to less than 6000. Radio and television sales were the main area of activity until the renewed demand for defence products with the Korean War. From a turnover of £5 million in 1949/50 there was an increase to £32 million in 1959/60.

In 1951 the Electronics Division was started by Michael Clark. By 1955 this had expanded to become the Electronics and Equipment Group with 5000 staff. The following year the Roke Manor Research Limited facility was set up under the direction of H.J. Finden. In the 1960s the Group continued to expand, setting up facilities at places such as West Leigh and Templecombe.

In 1961 Plessey merged with the British Ericsson Telephone Company, and the Automatic Telephone & Electric (AT&E), to become Britain's largest manufacturer of telecommunications equipment including the majority of the country's crossbar switches. Alongside the Telecommunications Division, three other businesses were set up: Plessey Avionics and Communications, Plessey Radar and Plessey Marine. In 1970 the Command and Control unit was set up at Christchurch, which became the centre of the Plessey Defence Systems business. In 1979 a major subsidiary was set up, Plessey Electronic Systems Ltd, which incorporated the three businesses and achieved sales of over £500 million and employed 15000 people by 1986.

Plessey were partners in the development of the Atlas Computer in 1962 and in the development of Digital telephone systems—System X—during the late 1970s. The Plessey Telecommunications Division merged with that of GEC to become GEC-Plessey Telecommunications. Plessey Naval Systems was formed in 1986 by the merger of Plessey Marine with Plessey Displays, which had been part of Plessey Radar.

In 1967 or 1968 English Electric was subject to a takeover bid by Plessey, but chose instead to accept an offer from GEC.

During the 1970s and early 1980s, Plessey manufactured a series of computer systems and peripherals compatible with Digital Equipment Corporation's PDP-11. By 1972 Plessey designed the first industrial Capability-based security computer, a fault-tolerant multiprocessor system called Plessey System 250. Plessey was also the lead contractor for the Ptarmigan communications system supplied to the British Army that adopted the Plessey System 250 architecture.

Exchange Works

After WW2, AT&E, later Plessey, became the Prime Contractor for a new UK Air Defence System, known by the Company under the cover name Project Linesman. To enable the system to be designed and built without too much information becoming public knowledge, a new factory called "Exchange Works" was built in Liverpool city centre, where young employees were granted exemption from conscription.

Heart of the system, installed in a huge building in the middle of a council housing estate in West Drayton, was the computer room, occupying an area of around 300 x 150 feet and filled with around 1000 seven foot high racks of electronics including mainly the XL4 computer, based entirely on germanium transistors and using a computer language developed at Exchange Works in the 1950s and 60s. During this period the company effectively became the world leader in computer design... unfortunately this fact remained a close secret.

The secure status of the factory attracted many other secret contracts and led to it becoming one of the major designers and manufacturers of cryptographic equipment. Exchange Works is now luxury flats.

Plessey in South Africa

The South African roots of Plessey can be traced to the acquisition of AT&E and Ericsson in 1963 and a Cape Town based company, the Instrument Manufacturing Company (IMC), acquired in 1964.

At the time, IMC was in the process of industrialising a unique South African invention, the Tellurometer, the first successful microwave electronic distance measurement equipment (EDM). The Tellurometer was invented by Dr. Trevor Lloyd Wadley of the Telecommunications Research Laboratory of the South African Council for Scientific and Industrial Research (CSIR), also responsible for the Wadley Loop receiver, which allowed precision tuning over wide bands, a task that had previously required switching out multiple crystals. The Wadley Loop was first used in the Racal RA-17 a 1950s top of the range British military short wave receiver still considered one of the finest radio receivers ever made and later in the South African made commercially available "Barlow-Wadley XCR-30" radio.

The Tellurometer design yielded high accuracy distance measurements over geodetic distances, but it was also useful for second order survey work, especially in areas where the terrain was rough and/or the temperatures extreme. The original Tellurometer, known as the Micro-Distancer M/RA 1, used a continuous wave at 3,000 megahertz, modulated by 10 megahertz and three other nearby frequencies. The remote station reradiated the incoming wave in a similar wave of more complex modulation, and the resulting phase shift was a measure of the distance travelled. The results appeared on a cathode ray tube with circular sweep. This instrument could penetrate haze and mist in daylight or darkness, and had a normal range of 30-50 km. It was covered by patents in at least eleven countries granted to Wadley and assigned to the CSIR. Under the Plessey mantle, Tellurometer (Pty) Limited was formed, which proceeded to manufacture the product and to develop and sell derivatives for decades to come. The subsequent years saw the introduction of numerical displays, solid state transmitters, integrated circuits and eventually microprocessors, all of these being adopted and mastered by a vibrant development team. A wide range of point to point microwave EDMs was produced, including the MRA7, which could measure distance up to 50 km with an accuracy of 15 cm, is still produced in limited numbers today. The product range included a 100km position fixing system, with fixed remote stations and a ship borne master station as well as three optical EDMs, the last of which was able to measure up to 1 km with an accuracy of 0.6 mm.

South African insurance and investment company Sanlam bought 26% of Plessey South Africa in 1974 with first right of refusal to purchase more of the company. These shares were later transferred to Sankorp, Sanlam’s industrial holdings company. Fifteen years later, in 1989, GEC-Siemens took control of the Plessey Company plc and Sankorp indicated its intention to purchase the remaining 74% of shares in the South African subsidiary.

GEC takeover bid

In December 1985 GEC launched a takeover bid for the Plessey Company, valuing the group at £1.2 billion. Both Plessey and the Ministry of Defence were against the merger, GEC and Plessey were the two largest suppliers to the MoD and in many tenders the only competitors. In January 1986 the bid was referred to the Monopolies and Mergers Commission (MMC), whose report published in August advised against the merger. The government concurred and blocked GEC's bid.

In 1988 Plessey and The General Electric Company (GEC) merged their telecom units to form GEC-Plessey Telecommunications (GPT), the UK's leading telecommunications manufacturer.

GEC Siemens takeover

In 1988 GEC and Siemens AG set up a jointly held company, GEC Siemens plc, to launch a hostile takeover of Plessey. GEC Siemens' initial offer was made on 23 December 1988 valuing Plessey at £1.7 billion. Again Plessey rejected the offer and again it was referred to the MMC. The original proposal envisaged joint ownership of all of Plessey's defence businesses, with GPT and Plessey's North American businesses split in the ratios 60:40 and 51:49 respectively. The level of GEC's involvement in the Plessey defence businesses was not likely to meet with regulatory approval and in February GEC Siemens announced a new organisation. The takeover was completed in September 1989. In April 1990 GEC and Siemens agreed a new structure of ownership of the Plessey businesses:

GEC acquisitions

  • UK
    • Plessey Aerospace
    • Plessey Avionics
    • Plessey Crypto
    • Plessey Materials
    • Plessey Naval Systems
    • Plessey Semiconductors
    • Plessey Research Caswell
  • North America
    • Plessey Aero Precision Corp
    • Plessey Dynamics Corp
    • Plessey Electronic Systems Corp (including ES Marine Systems)
    • Sippican Inc
    • Plessey Materials Inc
    • Leigh Instruments

Siemens acquisitions

  • Siemens Plessey Radar
  • Siemens Plessey Defence Systems
  • Siemens Plessey Controls
  • Siemens Plessey Australia
  • Siemens Plessey Assessment Services
  • Roke Manor Research Limited

Jointly owned

  • GEC-Plessey Telecommunications (GPT): 60% GEC and 40% Siemens


  • Birkby Plastics
  • Hoskyns Group
  • Plessey Spa (Italy)
  • 51% share in Plessey Telenet acquired by minority partner in 1992.
  • 74% share in Plessey South Africa

Subsequent history

In 1997 British Aerospace and Daimler-Benz Aerospace acquired the UK operations and German part of Siemens Plessey Systems, respectively. In 1999 Siemens acquired GEC's interests in Siemens Plessey. GEC acquired Siemens' 40% interest in GPT the same year, renaming it Marconi Communications.

GEC Plessey Semiconductors (GPS) was purchased by Mitel Semiconductors of Canada in 1998. After a number of downsizes, including the power semiconductor and silicon on sapphire operation at Lincoln, Lincolnshire being purchased in January 2000 by Dynex Semiconductor, the company renamed itself Zarlink Semiconductor in 2001. The GPS fab in Plymouth was acquired by Xfab and still houses a small Zarlink test facility.

In South Africa, following the successful GEC/Siemens takeover, after protracted negotiations, in 1991 Plessey South Africa became a wholly owned subsidiary of Sankorp under the new name of Plessey Tellumat South Africa Limited (PTSA). The addition of the name Tellumat had a double symbolism, firstly for the company's commitment to exports, as it is the name of its UK-based export subsidiary. Secondly the name derives from the Tellurometer South Africa's world first electronic surveying development—and by implication a commitment to ongoing electronic research and development.

Plessey Tellumat continued to grow, with a strong focus on telecommunications and defence products and solutions and particularly with a major expansion into large projects, rolling out the microwave backbone of MTN, one of South Africa’s first GSM cellular networks and the installation of a fibre optic network and radio broadcasting system in Malaysia. A software division was formed through the acquisition of BSW data, largely staffed by engineers from the recently-terminated South African space programme, in which Plessey had also participated, both in the electronics of the launch vehicle and the satellite itself.

1995 was a landmark year in the history of Plessey in South Africa. The merger of PTSA and Tek Electronics, the consumer electronics audio and video products, manufacturer and distributor, (also wholly-owned by Sankorp) took Plessey full circle back to its consumer electronics roots. This resulted in the renaming of PTSA back to the original name of Plessey South Africa Limited. The acquisition of Amalgamated Wireless Australia (AWA) which had a similar product portfolio, resulted in penetration into the Pacific Rim market. The culmination of this growth was the company’s listing on the Johannesburg Stock Exchange (JSE) as the Plessey Corporation in the same year. Trading started off at R4.80 a share. On the evening of the 6th of February 1996, a devastating fire swept through 2 bays of the White Road factory in Retreat, Cape Town causing huge damage to stock, instruments, plant and work in progress. No one was injured, but work was disrupted for several weeks. Large sections of the factory had to be rebuilt.

At the end of 1996, Plessey sold off the Sales and marketing business of Telefunken, Pioneer and Satellite TV. The manufacturing facility in East London was retained.

In August 1998 Plessey was bought by Dimension Data Holdings and World-wide African Investment Holdings for R1.6 Billion. The new owners retained BSW Data, Plessey Solutions and Communications Systems. The remaining divisions, notably with a product development and manufacturing focus, were bought back by a combined management buyout supported by Rand Merchant Bank. The corporate name was changed to Tellumat Pty Ltd ([]).

Tellumat continues to develop and manufacture Plessey-branded products as before and operates in the Defence, Telecommunications and Contract Manufacturing Markets.

Plessey barcodes

The name is also used to refer to a barcode symbology developed by Plessey, which is still used in some libraries and for shelf tags in retail stores, in part as a solution to their internal requirement for stock control. The system was first used in the early 1970s by J.Sainsbury to identify all of its products on supermarket shelves for its product restocking system. The chief advantages are the relative ease of printing using the dot-matrix printers popular at the time of the code's introduction, and its somewhat higher density than the more common 2 of 5 and 3 of 9 codes.

Plessey barcodes use two bar widths. Whitespace between bars is not significant. The start element is a wide bar, and the stop element is two narrow bars. In between, the bars are in groups of four. High order bars appear leftmost. Narrow bars are zero and wide bars are 1.

This symbology is not self checking, though a modulo 10 or modulo 11 checksum (depending on application) is usually appended.


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