Operated at 4 volts the tube has a life of 800 hours. The R was supplied to the British Army and was a general purpose vacuum triode similar in design to the French TM and to the British R. In the early productions the Moorhead tube used a spherical bulb and a vertical plate assembly, while the British R used a horizontal plate structure. The tube is fitted with a base made by the Shaw Insulator Company, who were associated with Moorhead Laboratories
