The Intermatic KM2ST-3D In-Wall 24 Hour 20A SPST Mechanical Timer replaces a standard wall switch (toggle) to provide automatic control of outdoor or indoor lighting, fans, pumps, office machines, and other types of circuits. Captive trippers are easy to set and can not be lost. 72 trippers provide up to 36 ON/OFF events in a 24 hour period. A three way, OFF/AUTO/ON override switch provides continuous ON or OFF positions. The Mechanical Timer is easily wired and installed and is UL listed. A three-gang decora-style wall plate is included. Single Pole, Single Throw (SPST) indicates the Timer can control one circuit (one set of lights, a spa pump, a fan, etc.) at the same time.