A reed switch is a none contact electronic switch that opens and closes as a magnet moves in and out of proximity.
They are great for protecting opening zones where a conventional plunger switch would not be practical. Common uses are Ute canopy windows, Ute hard lids, and camper van doors.
The Magnet is generally fitted to the item that moves and the switch to the vehicle. If the magnetic contact is broken (magnet moves out of range) then the alarm triggers.
The are other uses, for example I have fitted them into the glove box on vehicles so it turns on a LED to light up when the door is opened. As the magnet works through plastic it is totally hidden.
The photos show a reed switch which I installed on a hard Lid of a Toyota Hilux.
Being a builders vehicle I knew there was a danger of the switch getting knocked off so made up a custom metal bracket to protect if from abuse.
Autowatch make a wireless reed switch that works with some of their alarms.
