https://www.sparkfun.com/magnetic-door-switch-set.html
Magnetic Door Switch Set - SparkFun Electronics
SparkFun Electronics is an online retail store that sells the bits and pieces to make your electronics projects possible.
magnetic door switchsetsparkfunelectronics
https://www.newegg.com/p/0YH-0089-002C4
Unique Bargains 5pcs RC-33 NC Recessed Wire Door Contact Sensor Alarm Magnetic Reed Switch Brown -...
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