RETMA tube designation
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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
