The

Radio Electronics Television Manufacturers' Association The Consumer Technology Association (CTA) is a standard and trade organization representing 1,376 consumer technology companies in the United States. CTA works to influence public policy, holds events such as the Consumer Electronics Show (CE ...

was formed in 1953, as a result of mergers with other trade standards organisations, such as the RMA. It was principally responsible for the standardised

nomenclature Nomenclature (, ) is a system of names or terms, or the rules for forming these terms in a particular field of arts or sciences. The principles of naming vary from the relatively informal naming conventions, conventions of everyday speech to the i ...

for American

vacuum tubes A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied. The type known as a ...

- however the standard itself had already been in use for a long time before 1953; for example, the

6L6 6L6 is the designator for a beam power tube introduced by Radio Corporation of America in April 1936 and marketed for application as a power amplifier for audio frequencies.J. F. Dreyer Jr."The Beam Power Output Tube" New York: McGraw-Hill, ''Ele ...

was introduced in July 1936. American-made tubes bear a RETMA designation to allow for easy cross-referencing. The RETMA tube designation does not incorporate the purpose of each tube in the designation. The Anglo-European

Mullard–Philips tube designation In Europe, the principal method of numbering vacuum tubes ("thermionic valves") was the nomenclature used by the Philips company and its subsidiaries Mullard in the UK, Valvo( de, it) in Germany, Radiotechnique (''Miniwatt-Dario'' b ...

does include tube use information in the designation. *First figure group: indicates heater/filament voltage; 0 means a cold-cathode tube. * Letter group: letter(s) indicate the serial order of assignment of the designation; combinations like AB, AC, AD, AE... were used, avoiding same-letter repetitions, after the single letters were exhausted. Wherever possible, the 12V equivalent of a 6V tube had the same letters, just 12 instead of 6. :*L as a first letter often indicates a lock-in (Loktal) tube. :*P as a second letter from the end indicates a CRT. :*Letters U, V, W, X, Y and Z are commonly used for rectifiers :Occasionally the same letter groups were used for differing tubes but only where the last number would be different making the designation unique. For example there is a 12AV5 (beam tetrode), 12AV6 (double diode, triode) and a 12AV7 (double triode). *Second figure group is the number of useful elements (including the heater if this is separate from the cathode); in metal tubes the shell counts as one element. Internal shielding also counts, but base shielding does not. Electrodes connected together internally are counted as one element. There is an inconsistency in the way tapped heaters or filaments are counted. For example, the 12BH7 (double triode with separate cathodes) counts the center tapped heater as one useful element, whereas the 12BY7 (pentode) counts the center tapped heater as two useful elements. There are also inconsistencies in the way internal screens are treated. In the 6BX6 (pentode with g3 brought to its own pin), the screen around the assembly is not counted, whereas the 6BR7 (also a pentode with g3 brought to its own pin) has its similar screen included. :In the case of a CRT, the second figure group indicates the type of

phosphor A phosphor is a substance that exhibits the phenomenon of luminescence; it emits light when exposed to some type of radiant energy. The term is used both for fluorescent or phosphorescent substances which glow on exposure to ultraviolet or vi ...

the tube face was coated with. *Optional letters: :*A, B, C Improved backward compatible versions :*E Export version :*G Glass bulb, ''Shouldered Tube'' ST-12 to ST-16 size :*GT Glass bulb, T-9 size (actually 'Glass Tubular') :*GT/G Glass bulb, T-9 size interchangeable with G and GT types :*L Loktal :*LM Loktal-metal :*LT Locking base :*M Metal envelope :*MG Metal-glass :*ML Metal-Loktal :*S Spray shielded :*W Ruggedised, or military grade :*WA, WB Improved, backward compatible military/industrial variants :*X low loss ceramic base for RF use :*Y low loss

mica Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into extremely thin elastic plates. This characteristic is described as perfect basal cleavage. Mica is ...

-filled

phenolic resin Phenol formaldehyde resins (PF) or phenolic resins (also infrequently called phenoplasts) are synthetic polymers obtained by the reaction of phenol or substituted phenol with formaldehyde. Used as the basis for Bakelite, PFs were the first commerc ...

("Micanol")Tube Bases and the Asbestos Hustle
/ref> base for RF use

References

See also