Abstract: A photoelectric load control system for applying a.c. power to a street light as a function of ambient light level includes switching means for selectively applying a.c. power to a street light for turning the street light on and off; a trigger circuit having two states, a first state which actuates the switching means to turn on the street light and a second state which actuates the switching means to turn off the street light; means for biasing the trigger circuit into one of the states; and photoelectric sensing means for varying the bias on the trigger circuit to drive it into the other state in response to the ambient light level sensed by the photoelectric sensing means.

Abstract: In the device disclosed, a load is energized from energy-carrying lines. A detector responsive to a cyclically recurring physical condition, such as daylight, places a switch either in an operating mode or an idling mode in response to the absence of the condition. A control shifts from an idling mode to an operating mode in response to the detector being in a given one of its modes and shifts back to the idling mode after a given time less than the period of the cyclically recurring physical condition. A circuit responds to the control being shifted to its operating mode in response to the given one of the modes of the detector and responds to the detector simultaneously being in the operating mode so as to connect the lines to the load.