... by AF. Automatically detect illumination,When the light is below 7Lux, only make a sound over 52dB± ... detect illumination. When in daytime and the illuminatin is high, it won’t work. Only at night ... , Installation of the switch is the same as the ordinary switch using 2 wires. It is easy to operate.4, ... Some energy-saving lamp which has special functions can use 3 wires, such as ...