Standard Telephones and Cables Ltd (later STC plc) was a British manufacturer of telephone, telegraph, radio, telecommunications, and related equipment. During its history, STC invented and developed several groundbreaking new technologies including pulse-code modulation (PCM) and optical fibres.

The company was founded in 1883 in London as International Western Electric by the Western Electric Company, shortly after Western Electric became the telephone equipment supplier for the American Telephone and Telegraph Company (AT&T) in the United States. In 1925, Western Electric divested itself of all foreign operations and sold International Western Electric to International Telephone and Telegraph (ITT), in part to thwart antitrust actions by the American government. In mid-1982, STC became an independent company and was listed on the London Stock Exchange; for a time it was a constituent of the FTSE 100 Index. It was bought by Nortel in 1991.

The company was established in 1883 as an agent for Western Electric, which also had a factory in Antwerp, Belgium. The London operation sold US-designed telephones and exchanges to fledgling British telephone companies. Because of the costs of importing products, the company purchased a failing electrical cable factory at North Woolwich in London, in 1898. In addition to making lead-sheathed cables, the factory started assembling equipment from components imported from Belgium and the US, and subsequently introduced manufacturing. The company was incorporated as a British legal entity in 1910.

World War I brought its progress to a sudden halt. The company contributed to the war effort in military communications with its cable and wireless technologies. With radio technology rapidly developing in the USA after the war, Western Electric had an advantage when radio broadcasting was introduced in Britain. As well as manufacturing radio receivers, the company, in a consortium with its competitors, set up the British Broadcasting Company (BBC) in 1922. Electron tube technology was commercially exploited.

In 1925, Western Electric sold off its international operations, as well as the general electrical equipment merchandizing operations. The buyer of the international operations was the infant ITT Corporation, founded by Sosthenes Behn less than ten years previously with an aggressive and thrusting reputation. To fit with its other worldwide operations, ITT renamed its new UK operation Standard Telephones and Cables, its name implying a standard against which others would be measured. The new organization employed entrepreneurial risk taking, based on solid research and brave innovation.^{[citation needed]}

In 1933, Brimar was established to manufacture American-pattern electron tubes at Foots Cray, adjacent to the Kolster-Brandes factory.

Within a few years, multi-channel transmission (1932), microwave transmission (1934), coaxial cabling (1936), the entire radio systems for the liners Queen Mary and Queen Elizabeth (1936–39), the patenting of pulse-code modulation (1938) all contributed to the hey-day of telephony's development.

Between 1939 and 1945, significant military work was undertaken with many developments particularly with regard to aerial warfare: communications, radar, navigational aids, and especially OBOE