BS 3224-F-F3:1973

Specifies the photometric performance and the essential mechanical and electrical features (excluding lamps) of blister type high intensity bi-directional fittings providing illuminated guidance of the centre line of taxiways or taxi-routes over other paved areas at civil land aerodromes. The fittings normally emit green light but if adapted to emit red light they may be used as taxiway stop bar lights.