Marconi's "Wireless Telegraph and Signal Company" was formed on 20 July 1897 after granting of a British patent for wireless in March of that year. The Company opened the world's first radio factory on Hall Street in Chelmsford in 1898 and was responsible for some of the most important advances in radio and television. These include

• The diode valve in 1904
• Transatlantic tests
• High Frequency tuned broadcasting
• Formation of the British Broadcasting Company (later to become the independent BBC)
• Formation of the Marconi Wireless Telegraph Company of America (later RCA)
• Formation of Marconi Marine (1904)
• Short wave beam broadcasting
• Radar
• Television
• Avionics

Marconi's Wireless Telegraph Training College was set up in 1901. Along with private entrepreneurs, Marconi company formed in 1924 the Unione Radiofonica Italiana (URI), which was granted by Mussolini's regime a monopoly of radio broadcasts in 1924. After the war, URI became the RAI, which lives on to this day.

In 1939 the Marconi Research Laboratories at Great Baddow were founded and in 1941 there was a buy out of Marconi-Ekco Instruments to form Marconi Instruments.