This is an archived website which has not been updated since 2002.
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Decoding Valve, Transistor and CRT Numbers
Military Valves

British Army

Letters followed by digits. The letter part gives the valve type as follows :

ACR - Army CRT
AR - Army receiving valve (generally triode)
ARD - Army receiving diode
ARDD - Army receiving double diode
ARH - Army receiving hexode
ARP - Army receiving pentode
ARS - Army receiving screen grid (tetrode)
ARTH - Army receiving triode hexode
ARTP - Army receiving triode pentode
AT - Army transmitting valve (generally power triode)
ATP - Army transmitting Pentode
ATS - Army transmitting Screen Grid (Tetrode)
AU - Army Rectifier
AW - Army Stabiliser

British Royal Air Force

Again the code consists of letters followed by digits. The letters have the following meanings :

VCR - Valve cathode ray (CRT)
VGT - Valve gas triode (thyratron)
VI - Valve indicator (tuning eye)
VR - Valve receiving (general receiving valve)
VS - Valve stabilising (gas stabiliser)
VT - Valve transmitting (general transmitting valve)
VU - Rectifier

British Royal Navy

Another letters followed by digits code. The letters give the type of the valve, as follows :

NC - Navy CRT
NGT - Navy gas triode (thyratron)
NR - Navy receiving valve
NS - Navy stabiliser
NT - Navy transmitting (or power) valve
NU - Navy rectifier

Other British series

CV (common valve) numbers replaced the above three codes during WW2. There is no way to decode these by simple inspection of their number. ZA and 10E are also used as prefixes to catalogue numbers. For example UHF ‘horned’ triode 10E/392 is also equivalent to ZA 3055, VR 135, NR 80, CV 1135 and E 1148. On British Post Office components, VT means either Valve, Thermionic or Valve, Transistor [i.e. a transistor, not a valve] according to context.

French Army

Originally numbered in the TM (Télégraphie Militaire) series with the letters TM followed by the type number. There was also an ‘11’ series of all-metal construction with octal base and equivalent to comparable American types but using 11-volt heaters. Thus 11L6 was similar to 6L6 but using 11-volt heaters. Valves marked ECMR indicate French army origin (Établissement Centrale du Matériel Radio-télégraphique militaire.

German Defence (Reichswehr)

Most German army valves use a special base and bear codes in the format: two letters, two digits, one letter and two digits.

First letter

R - Reichswehr (Defence), includes both Wehrmacht (Army) and Kriegsmarine (Navy)

Second letter

D - Dekametric wavebands
G - Rectifier (Gleichrichter) or diode
K - Cathode ray tube
L - Transmitting or Power
V - Amplifier (Verstärker)

First number

Heater voltage

Third letter

A - Cathode ray indicator
D - Dual anode
G - Rectifier or diode
H - Hexode
L - Speed modulation
M - Magnetron
P - Pentode
T - Triode

Final number

This indicates the maximum power output in watts if the valve is a power tube, the coefficient of amplification if an amplifier or maximum rectified current if a rectifier.

A different scheme was used by the Air Force, employing two letters and a number. The number is a simple type number, issued progressively as each new valve was registered.

First letter

L - Luftwaffe (German Air Force)

Second letter

B - Cathode ray tube
D- Dekametric waves
F - Special type
G - Rectifier or diode
K - Stabiliser
M - Magnetron
S - Transmitting, wavelengths above 1 metre
V - Amplifier, wavelengths above 1 metre

Exceptions to this scheme include SA (rectifier), SD (triode) and SF (pentode), all using 1.9V heaters.

Other markings commonly found include Eigentum der RLM (air ministry property; RLM stood for Reichsluftfahrtsministerium which was the Government agency responsible for research and development of aircraft and avionic systems), Kriegsmarine (navy) and Wehrmachtseigentum (army property). BAL means Bau Aufsicht Luftfartsministerium, i.e. Air Ministry Inspection.

US Army - Signal Corps

VT numbers are USA military valves, with no way of decoding their pattern without look-up tables, although many valves were dual-marked with VT and civilian part numbers.

US Navy

Before the Joint Army Navy (JAN) plan was implemented in 1942 the Navy used two different numbering systems. The first scheme was placed in service just before World War One, and was fairly simple - the first letters described who built the device (SE for the Bureau of Steam Engineering, C* for a civilian contractor, for example CG for General Electric), and the number was simply assigned sequentially. About 1932, a new scheme was introduced that would describe the parts better, using some of the old scheme to help. The "C" contractor code was kept and greatly expanded and of the digits following, the first two designated the class, the following three the specific type number. This system stayed in service until the outbreak of World War Two, when it was dropped due to the huge influx of new tube types. The Navy did not immediately jump completely to the AN nomenclature system in 1942, however, placing some systems under the old Navy Model Letter/Type Number system and others under the new AN system. (Ray Mote’s two-part article in the June and July 1995 issues of Electric Radio magazine covered this topic).

Standard military marking requirements for parts are now (normally) as follows: Part Number (usually the NSN = National Stock Number), Cage Code (= prime contractor), Date code (or lot date code), contract number, and other sundry markings per specific contract. There is a good search engine for the Cage Code (and other goodies):

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