Vacuum tubes produced in the former Soviet Union and in present-day Russia carry their own unique designations. Some confusion has been created in "translating" these designations, as they use Cyrillic rather than Latin characters. 1929 system The first system was introduced in 1929. It consisted of one or two letters and a number with up to 3 digits denoting the production number First letter: System type: B (Russian: Б) – Power oscillator tube or barretter V (Russian: В) – Rectifier G (Russian: Г) – Transmitting tube ("генераторная" "generator") J (Russian: Ж) – Low-power oscillator tube M (Russian: M) – Modulator N (Russian: Н) – AF amplifier P (Russian: П) – Receiver tube S (Russian: С) – Special tube, such as a tetrode, a pentode or a CRT T (Russian: Т) – Carrier frequency tube U (Russian: У) – Amplifier tube Second letter (optional): Type of cathode: B (Russian: Б) – Barium-coated K (Russian: К) – Carburized O (Russian: О) – Oxide-coated T (Russian: Т) – Thoriated C (Russian: Ц) – Caesium-coated Examples: VO-116, VO-188, VO-202 (Russian: ВО-116, ВО-188, ВО-202) Full-wave rectifiers with an oxide-coated cathode SO-118 (Triode), SO-122 (Power pentode), SO-124 (Tetrode) (Russian: СО-118, СО-122, СО-124) 4-volts indirectly heated tube set for premium radios SO-148 (Russian: CO-148) Variable-mu tetrode with an oxide-coated cathode SO-242 (Russian: СО-242) Heptode with an oxide-coated cathode UB-110 (Russian: УБ-110) Triode with a barium-coated cathode In 1937, the Soviet Union purchased a tube assembly line from RCA, including production licenses and initial staff training, and installed it on the Svetlana/Светлана plant in St. Petersburg, Russia. US-licensed tubes were produced since then under an adapted RETMA scheme; for example, the 6F6 thus became the 6Ф6. Receiver tubes In the 1950s a 5-element system (GOST 5461-59, later 13393-76) was adopted in the (then) Soviet Union for designating receiver vacuum tubes. The 1st element (from left to right) is (for receiving tubes) a number specifying filament voltage in volts (rounded to the nearest whole number). The 2nd element is a Cyrillic character specifying the type of device: D (Russian: Д) – Diode, including damper diodes. H (Russian: Х) – Double diode. C (Russian: Ц) – Low-power rectifier (kenotron). S (Russian: С) – Triode. N (Russian: Н) – Double triode. E (Russian: Э) – Tetrode. P (Russian: П) – Output pentode or beam tetrode. J (Russian: Ж) – Sharp-cutoff pentode (also transliterated zh, sh or j). K (Russian: К) –