For Alexa or Google Home, this four-pack of contact sensors will give you the best bang for ... home technology, door sensors acted as one of the major parts of a home alarm system.

There’s a huge market for 433 MHz alarm system hardware out there, from PIR motion detectors to door and window sensors. If you want to put them to work, all you need is a receiver, a network ...

[Jeff Sandberg] demonstrates that ably with his project to use ancient 1990s burglar alarm ... sensors themselves sit on doors or windows. They use magnets and a reed switch to sense if the door ...