This component can be used in a circuit to open and close a contact when exposed to alternating N and S poles of a magnet. Will also work if exposed to the same pole on alternative sides of the sensor.
Many uses including:
Counting revolutions, oscillations, or sequences
Turning LEDs, alarms, or other devices on/off
Detecting presence of magnetized materials
Monitor start/stop of a moving process
Robotic effects and magic tricks!
Schematic of an example circuit included. Part number may vary from picture. Very unique!