Electrometer tube The next elements are: Ignitrons, Rectifier tubes, Thyratrons: A digit A dash ("-") Anode current in A A slash ("/") Anode voltage in kV A letter specifying the cooling method: <none> – Radiation A (Russian А) – Water Transmitting tubes: A dash ("-") A sequentially assigned number A letter specifying the cooling method: <none> – Radiation A (Russian А) – Water B (Russian Б) – Air P (Russian П) – Vapor Phototubes and Photomultipliers: A dash ("-") A sequentially assigned number One or two letters: V (Russian В) – Vacuum G (Russian Г) – Gas-filled S (Russian С) – Caesium-activated antimony cathode C (Russian Ц) – Caesium cathode Popular transmitter tubes include the ГУ-29, ГУ-50, ГМ-70 and Г-807 (the Russian 807 analogue). See also List of vacuum tubes Mullard–Philips tube designation RMA tube designation RETMA tube designation References External links Explanation of tube designation systems (in English) Russian receiver tube designation system (in Russian) Vacuum tubes Electronics lists Tube designations