Through-Beam Photoelectric Sensor Through-Beam sensors have the emitter and the receiver in their own separate component. For the Through-Beam sensor to work, the emitter and receiver have to be pointed at each other and be aligned. When they are aligned, and nothing is blocking the light, the output of the sensor will be on. If you put something between the emitter and receiver to block the light, the output of the sensor will turn off. The sensor’s output is the signal from the sensor to the P