Vacuum tube numbering systems

- for all types of thermionic valve or vacuum tube including the diode, triode, tetrode, pentode, heptode, etc . . .

Vacuum Tube / Thermionic Valves Includes:
Basics How does a tube work Vacuum tube electrodes Diode valve / tube Triode Tetrode Beam Tetrode Pentode Equivalents Pin connections Numbering systems Valve sockets / bases Travelling wave tube

In order that vacuum tubes or thermionic valve numbering had some reason to it, numbering schemes were developed.

Using these it was possible to gain an approximate idea of the tube and its functions.

There are two schemes that were adopted, one used in Europe for valves primarily manufactured and used there, and the other for vacuum tubes from the USA. Although the numbering schemes were different, most valves or tubes were available with numbers in both systems.

Numbering systems

European System

First letter indicates the heater supply	Subsequent letters indicate the type of valve	Following figures indicate the base
A 4V AC C - 200mA AC and DC D - Battery supply 1.2 to 1.4V E - 6.3V AC and DC G - 5V AC K - 2V battery supply P - 300 mA U - 100 mA AC and DC	A - Single diode B - Double diode C - Triode D - Triode output valve E - Tetrode F - Pentode H - Hexode or heptode K - Octode L - Pentode output valve M - Tuning indicator N - Thyratron Q - Nonode T - Miscellaneous X - Gas filled full wave rectifier Y - Half wave rectifier Z - Full wave rectifier	20 - 29 B8G (Loctal) 30 - 39 Octal 40 - 49 B8A 50 - 59 Miscellaneous constructions 60 - 79 Subminiature constructions 80 - 89 B9A 90 - 99 B7G If a number is greater than a hundred then the first figure should be disregarded to determine the base.

American system

First figure indicates the heater voltage	Second and other characters are serial numbers	Suffix letters
0 - Cold cathode 1 - 0 - 1.6V 5 - 4.6 - 5.6V 6 - 5.6 - 6.6V 7 - 6.3V Loctal 12 - 12.6V 35 - Around 35V		G - Large glass envelope GT - Small glass envelope M - Metallised X - Low loss base W - Military type base