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.

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 22.5mm;
N – in a ceramic-metal environment, tiny and supertiny;
K – in a ceramic environment;
D – in a metal-glass environment, with disks.

V – increased reliability and mechanical ruggedness (such as low susceptibility to noise and microphonics);
R – even better than V, extra high reliability (10000 hours and more);
E – extended service life (5000 hours and more);
D – exceptionally long service life;
I – optimised for "pulsed" (i.e. switching) mode of operation.

6 – filament voltage, 6,3V;
P – output pentode;
14 – serial number of type of a tube;
P – envelope: miniature, glass;
ER – raised durability, operation time > 10000h

K – shortwave (≤ 25 MHz) tube;
U – ultra-shortwave (25–600 MHz) tube;
S – centimetric-wavelength (> 600 MHz) tube;
M – modulator tube;
I – impulse tube.