Captain H.J. Round, of the Marconi company, started work on his 'soft' valves in 1911; these were the first British triodes, following on from Fleming's original diode valves of 1906. Round valves were much used during the 1914-18 war, although a degree of skill was needed to get the best out of them. The Type N was used in the Type 16 and 27 receivers (other Round valves were the T and the C, for transmitting and receiving, respectively). The valves were made for Marconi by Ediswan, and could be had either with bayonet or screw bases. A match was found the simplest and best way of heating the pip to adjust the vacuum, although electrical heating had to be used on board aircraft.