RETMA tube designation

The Radio Electronics Television Manufacturers' Association was formed in 1953, as a result of mergers with other trade standards organisations.

They were principally responsible for the standardised nomenclature for American vacuum tubes.

American made tubes bear a RETMA designation to allow for easy cross-referencing. However, the RETMA tube designation fails to explain the purpose of each tube - unlike the Anglo-European Mullard-Philips tube designation.

*First figure group: indicates heater/filament voltage
* Letter group: letter(s) indicate the serial order of assignment of the designation.
**Letters U, V, W, X, Y and Z are commonly used for rectifiers
**S as a first letter indicates single-ended tubes, related to grid-cap tubes.
**S as a second letter indicates single-ended tubes.
**Combinations like AB, AC, AD and AE were used when all the single letters were used up.
**L as a first letter often indicates a lock-in (Loktal) valve.
**P as a second letter indicates a CRT.
**Wherever possible, the 12V equivalent of a 6V tube had the same letters, just 12 instead of 6.

* 2nd figure group is the number of useful elements; in metal tubes the shell counts as one element. Base shielding does not count.

*Additional letters:
*A,B,C Improved backward compatible versions
*E Export version
*G Glass bulb, ST-12 to ST-16 size
*GC Glass Compact
*GT Glass bulb, T-9 size
*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 HF use
*Y low loss phenolic (Micanol) base for HF use