Plessey Company
Cottenham Road, Ilford

The Plessey Company plc was a British 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 split the assets of the Plessey group.

Manufacturer of Radios and crystal sets for Marconi (from 1918), TV sets, electronic components and military equipment like the AC44 airborne transmitter receiver in the 1930s.

The manufacturer of the Baird's mechanic Televisor in the early 1930s.

Almost all UK companies used them for excess production. Almost all Defiant brand Radio sets from the Co-op made by Plessey. Some models for EMI (Marconi/HMV/Columbia), Cossor and Ever Ready in the mid to late 1940s.

Later Plessey diversified forming many different divisions, including; Plessey Radar, Plessey Avionics, Plessey Marine, Plessey Telecommunications and they became a leading international company.
Plessey Telecommunications was a major supplyer of Telephone Exchange Equipment for both private and public exchanges.

1917. 12th December. Plessey was founded in Marylebone, London as a mechanical an engineering concern.
1923 Plessey moved to larger premises in Ilford. At the time there were more than 200 employees.
Plessey’s diversification into radio and electronic manufacturing started with orders from Marconi for 2 types of crystal set and a valve receiver.
1928 Important contracts included production of telephones for the General Post Office (GPO) and items for the Air Force and the car industry. Production of equipment for professional customers became a growing part of the company’s business.
1929 John Logie Baird’s first production televisions were manufactured by Plessey. The company also produced the first British-made portable battery radio, the “National” which was supplied to Symphony and Columbia.
WWII - During the war, Plessey produced many different types of components and equipment for the war effort, including shell cases, aircraft parts, and radio equipment such as the R1155 (receiver) and T1154 (transmitter).

1951 The new Communications Division was formed. A licence was obtained from the US company Philco for the manufacture of semiconductors; the two companies set up a joint venture.
1957 Manufacture of transistors began in a new built factory at Swindon, one of the first semiconductor factories in the UK. Plessey also manufactured the first VHF/UHF airborne radio in the UK.

1961 Plessey had 23 subsidiary companies , employing 17,500 persons. These included designers and manufacturers of radio and television apparatus and components, electronic equipment, telecommunication equipment, electrical equipment, electrical instruments and commercial hydraulic power systems, makers of general light engineering products and atomic energy power control equipment.

Plessey took over two other telephone manufacturers, Ericsson Telephones Ltd and the Automatic Telephone and Electric Co, doubling Plessey’s size to become Britain's largest manufacturer of telecommunications equipment.

1966 MOS integrated circuits were produced at Swindon, making Plessey the first European manufacturer of such microcircuits.

1981 With the corporate focus on semi-conductor manufacture, radar systems and  telecommunications networks, the company divested parts of the business that did not fit.

1988 Plessey acquired Ferranti Semiconductors, creating Europe's largest semi-custom chip company. A new state-of-the-art silicon chip production facility near Plymouth was opened.

1989 The UK operating divisions were:

    Plessey Electronic Systems Ltd
        Plessey Radar
        Plessey Defence Systems
        Plessey Naval Systems
        Plessey Avionics
        Plessey Crypto

    Plessey Engineering and Components
        Plessey Semiconductors
        Plessey Three-Five Group
        Plessey Materials
        Plessey Aerospace
        Birkby's Plastics

    Plessey Controls Ltd

    Plessey Research and Technology
        Caswell Research
        Roke Manor Research

September, 1989 : Plessey was taken over by a consortium formed by GEC and Siemens which split the assets of the Plessey group.