Module Features: 1. Use imported groove coupler sensor. 2. Groove width:5mm. 3. Output state indicator lights. 4. Obscured output high; unobstructed output low. 5. The comparator output, the signal is clean, the waveform, driving ability, more than 15mA. 6. Operating voltage 3.3V-5V. 7. The output in the form: Digital switching outputs. (0 and 1) 8. A fixed bolt hole for easy installation. 9. Small plates PCB Dimensions: 3.2cm x 1.4cm. 10.Using a wide voltage LM393 comparator. Module Using The Instructions: 1. Module slot unobstructed, receiver tube conduction module DO output low, shelter, DO output high. 2 .Module DO connected to the relay, composed of the limit switch functions can also be connected to the active buzzer module, composed of the alarm.