Standard Telephones and cables used the STC brand for professional valves and the Brimar trade name for consumer valves.
The PDF file of the Standard Valves book courtesy of Tube Books.
The object of the commercial code is to enable classification of valves, cathode ray tubes, thermocouples, etc., to be made according to their electrical sizes and types, and to ensure that the technical information when filed in numerical order will group components of a similar type and rating together.
Where a valve has been marketed under a 4000 code (eg 4220C, 4357A, etc.), the valve should be referred to by that number.
The general valve coding takes the following form: a number indicates the number of electrodes; a letter which designates the type of valve, followed by a forward slash; a three figure number, the first two figures of which usually indicate the electrical size, the third figure being a serial number. The type of base is indicated by the letter following and in a few cases a further letter is used to denote physical or test limit variations.
Coding for special types such as cathode ray, cold cathode, velocity modulated tubes, etc., commences with a letter instead of a figure. The subsequent combination of figures and letters indicates electrical size, characteristics, serial number and basing according to the requirements of each type.
The second letter describes the type of valve:
Anode Dissipation below 10 Watts
Anode Dissipation between 10 and 100 Watts
Anode Dissipation between 100 and 1,000 Watts
Anode Dissipation between 1,000 and 10,000 Watts
Air Blast Cooled
Low Voltage Rectifier
High Voltage Rectifier
The double digits indicate actual anode dissipation and the following digit is a serial number.
The final letter identifies the valve base:
American Standard Base
British Standard Base
Ediswan Screw ES Base
International Octal IO Base
Mounted by Disc Seal
Miniature Button Base
Examples - General Valves
2 = diode, S = Low voltage rectifier, 30 = Function of Peak current and PIV 0 = serial number, A =- American standard base.
2 = diode, T = High voltage rectifier, 27 = function of Peak current and PIV 0 = serial number, K = miniature button base.
2 = diode, V = Mercury Vapour rectifier, 40 = function of Peak current and PIV 0 = serial number, C = Edison screw base.
22 = double diode, V = Mercury vapour rectifier, 3 = function of Peak current and PIV 0 = serial number, A = American standard base.
3 = triode, A = Anode dissipation below 10 watts, 10 = Anode dissipation 7 = serial number, B = British standard base.
3 = triode, B = Anode dissipation between 10 and 100 watts, 40 = Anode dissipation 40 watts, 1 = serial number, J = Mounted by disc seal.
3 = triode, V = Mercury vapour, 32 = function of Peak current and PIV 0 = serial number, B = British standard base.
3 = trlode, J = Air blast cooled, 17 = function of Peak current and Max. Anode voltage, 0 = serial number, E = Special base.
3 = triode, Q = Water cooled, 21 = function of Peak current and Max. Anode voltage, 3 = serial number, E = Special base.
33 = double triode, A = Anode dissipation below 10 watts, 10 = Anode dissipation, 0 = serial number, A = American standard base.
4 = tetrode, C = Anode dissipation between 100 and 1,000 watts, 80 = Anode dissipation 800 Watts, 0 = serial number, E = Special base.
5 = Pentode, A = Anode dissipation below 10 watts, 10 = Anode dissipation 10 Watts, 2 = serial number, D = International Octal base.
5 = Pentode, D = Anode dissipation between l,000 Watts and l0,000 Watts, 10 = Anode dissipation l,000 Watts, 0 = serial number, A = American standard base.
Examples - Ballast Lamps
IC = indicates the average stabilising current, C denotes the range 1 to 9A, current is 1 Amp, 1 = serial number, G = No base leads brought out.
4B = Indicates the average stabilising current, B denotes the range 0.1 to 9 Amp, current is 0.4 Amp, 2 = serial number, C = Edison screw base.
Examples - Cathode-Ray Tubes
16 = The approximate screen diameter 16/4 which is 4 inches, G = Gas focused, S = Electrostatic deflection, 1 = serial number, B = Colour of screen - blue.
22 = The approximate screen diameter, 22/4 which is 5.5 inch, S = Electrostatic focus, M = Magnetic deflection, 2 = serial number, G = Colour of screen - Green.
Examples - Cold Cathode Tubes
150 = The approximate minimum breakdown voltage of main gap, 2 = serial number, D = international Octal base.