This British Standard specifies the requirements for two basic sizes (A and B) of single-hole fixing, lever-operated manual switches for use in nominal 28 V d.c. and 115/200 V three-phase, 400 Hz a.c. systems in aircraft.
Two classes of environmentally sealed switches in each basic size are specified as follows.
Class 1. Switches suitable for high altitude and wide temperature conditions.
Class 2. Switches suitable for lower altitudes and narrower temperature conditions than class 1 switches.