Abstract: A photo controller circuit for use in hazardous areas has an output switching (OS) circuit comprising an alternistor for ON/OFF switching of a load, and an optoisolator for gating the alternistor. A light to voltage converter (LVC) circuit generates a DC voltage proportional to detected incident light. A hysteresis control (HS) circuit comprises a voltage comparator for generating an output depending on the DC voltage and the state of the OS circuit. An integrator and switching (IS) circuit turns on and activates the optoisolator when the output of the HC circuit indicates the detected incident light is below a selected level, and turns off and deactivates the optoisolator when the output of the HC circuit indicates the detected incident light is above a selected level. The IS circuit time delays the output of the HC circuit prior activating or deactivating the optoisolator. The electronic components are rated for 125° C.