The type nomenclature for the larger Mullard Transmitting and Industrial Valves generally consists of two or more letters followed by two sets of figures. These symbols provide information concerning the principal uses and ratings of the valves according to the following code. It is pointed out, however, that in a very few instances it has not been possible to adhere strictly to this code.
The first letter indicates the functional class of valve:
Note: For valves having a dual electrode system, the code letters for both systems are used. eg QQ for a double tetrode.
Backward Wave Amplifier
Forward Wave Amplifier
LF Amplifying or Modulator Triode
RF Power Pentode
RF Power Tetrode
RF Power Triode
Large Thyratron. All hydrogen thyratrons and other thyratrons having a maximum mean anode current of 500 mA or more.
The second letter indicates some structual property in each class of valve:
For transmitting valves and vacuum rectifiers, the type of cathode is indicated.
Indirectly Heated Oxide Cathode
Directly Heated Tungsten Filament
Directly Heated Thoriated-Tungsten Filament
Directly Heated Oxide-Coated Filament.
For thyratrons and gas-filled rectifiers, the type of gas present is indicated.
Inert Gas Filled
For microwave devices, a basic structural feature is indicated.
Outputs up to 1 Watt (For forward and backward wave devices)
Outputs of 1 Watt and over. (For forward and backward wave devices)
External Magnet Required. (For Magnetrons)
Packaged Construction in Magnetrons
Reflex (Single Resonator) construction Klystron
Multiple Resonator Construction Klystron
The third letter:
Transmitting Valves with a Silica Envelope
Thyratrons with a Shield Grid (Tetrode Construction)
Microwave devices that are Tuneable
The first group of figures immediately following the letters indicate:
For Transmitting Valves. The approximate anode voltage in kV. 05 = 500 Volts 2 = 2kV
For Thyratrons. The peak inverse voltage in kV
For Magnetrons, Klystrons, Forward and Backward Wave devices. The approximate frequency of operation in GHz.
The second group of figures indicates:
For transmitting valves, the maximum permitted anode dissipation in Watts. For dissipations in excess of 10 kW the dissipation in kW is given.
For transmitting valves primarily intended for pulse operation this group is prefixed by a P and the figures indicate the peak current in Amps.
For Backward Wave tubes and Forward Wave Amplifiers, the output power in mW or W. This depends on the second letter an A or B.
For Magnetrons, the pulse power output in kW
For Klystrons, the output power in mW
For Rectifiers, the approximate rectified current in mA
For Thyratrons, the approximate maximum permitted mean anode current in mA. This group consists of at least 3 digits. eg 045 = 45 mA, 6400 = 6400 mA or 6.4 A. 12 = 12 Amp.
A final letter occasionally follows the second group of figures. This is usually a serial letter to denote a particular design or development.
Forced air cooling
The TYS5-3000 decodes as an RF power triode with a directly heated thoriated-tungsten filament in a silica envelope. The maximum anode voltage is of the order of 5 kV and the anode dissipation is rated at 3000 Watts.
The RR3-250 decodes as a power rectifier with an inert gas filling. The anode voltage is approximately 3,000 Volts and the rectified current is 250 mA.
The QQZ06-40 decodes as a double tetrode with a directly heated oxide filament. The anode voltage ia approximately 600 Volts and the anode dissipation is about 40 Watts.