System of a designation of the Russian radio tubes, made in the USSR, made under the standard GOST 13393-76 and have usually four elements.
The first element - number, means a ailament voltage in volt (approximately).
The second element - letter, designating type of the device:
D - diode, including dempfers;
H - double diode;
C - low-power kenotron;
S - triode;
N - double triode;
E - tetrode;
P - output pentode and beam tetrode;
J - high-frequency pentode with short characteristic, including with double management;
K - high-frequency pentode with long characteristic;
R - double tetrode and double pentode;
G - diode-triode;
B - diode-pentode;
F - triode-pentode;
I - triode-geksode, triode-geptode, triode-oktode;
A - frequency-converting tubes and tubes with two operating grids (except for pentodes with double management);
V - tubes with secondary issue;
L - tubes with focused beam;
E - electron-beam indicators of adjustment.
For electronic mehatrons the second element of a designation is made of three letters: the first M - mehatron; the second letter corresponds to the basic purpose of the device (in some designations mehatrons, developed earlier, this letter is absent); the third letter designates type of the device according to the list resulted above.
The third element - number, corresponding a serial number of the given type of a tubes.
The fourth element - letter, describing constructive desing of a tubes:
P - in a glass environment, tiny (finger-type), diameter 19 and 22.5 mm;
A - in a glass environment, supertiny, diameter from 5 up to 8 mm;
B - in a glass environment, supertiny, diameter from above 8 up to 10.2 mm;
G - in a glass environment, supertiny, diameter over 10.2 mm;
S - in a glass environment, with a socle or without a socle, diameter more than 22.5 mm;
N - in a ceramic-metal environment, tiny and supertiny;
K - in a ceramic environment;
D - in a metal-glass environment, with disks.
Lamps in metal to an environment of the fourth element of a designation no have.
Additional element. To a standard designation of a tube are sometimes added (after a hyphen) the letters describing special properties of lamps, for example:
B - tubes of raised reliability and mechanical durability;
E - tubes of the raised durability (5 thousand hour and more);
D - tubes especially durable;
DR - made tube with super quality for USSR (CCCP) space (military and civil) needs;
I - tubes, intended for work in a pulse mode.
6 - filament voltage, 6,3V;
P - output pentode;
14 - serial number of type of a tube;
P - envelope: miniature, glass;
ER - operation time, >10000h
- Transmitter tubes
There is another designation system for high-power tubes such as transmitter ones.
The first element (from left to right) is always G.
The second element is:
K - shortwave (<= 25 MHz) tube.
U - ultra-shortwave (25-600 MHz) tube.
S - centimetric-wavelength (> 600 MHz) tube.
M - modulator tube.
I - impulse tube.
The third element consists of a dash ("-") followed by the design serial number. If the tube has to be force-cooled there might follow a letter 'A' for water-cooled or 'B' for air-cooled.
P.s. The 2nd element with some notable exceptions such as the G807.