This British Standard specifies the performance and quality requirements for bayonet lampholders for aircraft lamps having single centre contact (B 15s) caps and minia-ture centre contact (BA 9s) caps, intended for use in atmospheric pressures down to 522 millimetres of mercury (equivalent to an altitude of 10 000 ft (3048 m)). The lampholders are suitable for use on systems of nominal voltages up to 28 volts; they may be used on other nominal voltages subject to the following individual maximum limitations, which apply independently of each other:
B 15s: 2 amp, 250V r.m.s. a.c, 60 watts. BA 9s: 1 amp, 50V r.m.s. a.c, 10 watts.
Although BA lampholders are not recommended for general use in circuits operating at more than 50 volts, with neon indicator lamps BA 9s lampholders may be used on nominal system voltages up to 200V r.m.s. a.c, subject to a series ballast resistor being connected externally to the centre contact of the lampholder.
Outline drawings of preferred lampholders are shown, but these are not intended to restrict the development of types offering alternative installational facilities such as batten mounting.