This is a very simple module that contains a magnetic reed switch which will close its contacts when a magnet is placed nearby. The digital output pin will go high (+5V) when a magnetic field is in proximity. An on-board LED will also illuminate when the reed switch is closed. There is a potentiometer which appears to not serve much purpose, and which we believe is just there because the module is using generic circuit used designed for other modules.


Pinout
PIN 1: ANALOGUE OUT (?)
PIN 2: GND
PIN 3: VCC (+5V)
PIN 4: DIGITAL OUT