Designed to be operated in conjunction with the room light. When the light is switched on the fan starts, when the light is switched off the fan continues to run for the pre-set time (which is adjustable). IMPORTANT: Requires a permanent live, switched live and neutral connection (3 wires excluding earth) at the fan position in order for the timer functionality to operate correctly. If you do not require the timer function the permanent live and switched live connections can be linked out.