This 2-Channels Opto Sensor is consist of 3 parts: 2 opto-emitters and receivers, one PCBA to adjust the sensitivity and map out the signal. With this sensor, you can measure if there are the objects in the measuring range, eapacilly useful in applications that you need to monitor the inputs&outputs of a system.

When the opto sensor didn't covered , the D0 output logic LOW, the signal indicate LED light, when the opto sensor covered, the D0 output logic HIGH and the LED off, adjust the potentiometer can adjust the sensitivity of the sensor.