Sensor circuit, hall effect switch, Magnetic reed switch, Magnetic reeds

 MLX90217 Series 3.5 to 24 V 25 mA Through Hole Hall Effect Cam Sensor - TO-92-3

https://www.futureelectronics.com/p/semiconductors--analog--sensors--magnetic-hall-effect/mlx90217lua-caa-000-bu-melexis-2003565