Abstract: A flashing warning light apparatus wherein there is provided one or more light-emitting diodes, the light-emitting diode being driven in a pulsed manner to achieve light output at a selected flash rate, with control means adapted to detect any light induced signal from the same light-emitting diode or diodes during periods when the light-emitting diode is not emitting light, said signal being dependent on the level of ambient light. The same diode or diodes can be at a focus center of a reflector. A magnitude of any signal can then be used to determine whether the ambient light is such that the warning light should operate.