This is the MLX90324 Magnetic Hall Effect Monolithic Touchless Rotation Sensor developed by MELEXIS Semiconductor. This MLX90324 is a sensor that uses its signature called TriaXis Hall Technology means that it uses a magnetic force to drive this sensor. moreover,
The reed switch is an electrical switch which is operated by an applied with a magnetic field. When the magnet close the Reed Switch it will activate as HIGH, The Reed Switch was invented at Bell Telephone Laboratories in 1936.