1, imported normally open reed switch2, the comparator output, the signal is clean, the waveform, driving ability, more than 15mA.3, operating voltage 3.3V-5V4, the output in the form: Digital switching outputs (0 and 1)5, a fixed bolt hole for easy installation6,small board PCB size: 3.2cm x 1.4cm7, wide voltage LM393 comparator