This circuit shows an MOC3011 optoisolator used for remote control of ac voltages. Local building codes frequently require that all 115-V light-switch wiring be enclosed in conduit. With this circuit, it is possible to control a large lighting load from a long distance through low-voltage (5 V) signal wiring, which is completely isolated from the ac line. Such wiring usually is not required to be in conduit, so the cost savings (especially in large commercial or residential build-ings) can be considerable. Although a lighting load is shown, the load can be a motor, fan, pool pump, etc.