When the BBC first began transmissions on 14 November 1922, the technology for both national coverage and joint programming between transmitters did not exist – transmitter powers were generally in the region of 1 kilowatt (kW). Marconi began experimenting with higher power transmissions from a site in Chelmsford under the call sign "2MT" in July 1924. The experiments were successful, leading to the development of both shortwave international broadcasting and longwave national broadcasting, the latter with the call sign 5XX.