Mullard
Valve Type Nomenclature

All new Mullard valves are registered internationally with Pro-Electron 
and have type numbers according to the following code, based on the Pro-
Electron type nomenclature system for receiving and amplifying valves.

The type number consists of two or more letters followed by a group of 
three figures (two figures in earlier types).

The first letter indicates the heater or filament voltage or current:

        D        0.5 to 1.5V filament
        K        2.0V heater
        A        4.0V heater
        E        6.3V heater
        G        5.0V heater
        P        300mA heater
        C        200mA heater
        U        l00mA heater

The second and subsequent letters indicate the general class of valve:

        A        single diode
        B        double diode
        C        triode
        D        power output triode
        S        tetrode
        F        pentode
        L        power output tetrode or pentode
        H        hexode or heptode (hexode type)
        K        octode or heptode (octode type)
        M        tuning indicator
        Y        half-wave rectifier
        Z        full-wave rectifier

Two or three of these letters may be combined together, 
e.g. BC - double-diode triode.

The first figure of the serial number indicates the type of base:

        2        Bl0B (10-pin) base (previously used for B8G base)
        3        Octal base
        4        B8A base
        5        B9D (magnoval) base (previously used for miscellaneous 
                 bases)
        8        B9A (noval) base
        9        B7G base

The remaining figure or figures make up the serial number indicating a 
particular design or development.

Examples:-

        PCF8O6   Triode pentode with B9A base for use in 300mA series 
                 heater chain.
        EC9O     Triode with B7G base and 6.3V heater.

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