Security & Access Control — Door/Window Alarm & Elevator

- Nov 9, 2026-

The magnetic door contact is the most widely deployed reed switch application in the world, with billions installed in homes, offices, and commercial buildings. A reed switch in the door frame and a magnet in the door detect opening and closing without contact, without wear, and without power. The same simple principle also serves elevator position detection and access control.

Door and Window Intrusion Alarm

A reed switch is mounted in the door or window frame and a magnet is mounted in the moving door or window. When the door is closed, the magnet holds the switch closed. The moment the door is opened, the magnet moves away, the switch opens, and the alarm system is triggered. Because the switch is sealed and has no exposed contacts, it works reliably for years in any weather, and because it is passive it draws no power while the door is closed. Many systems add a second reed switch to detect tampering: if an intruder tries to hold the switch closed with a strong external magnet, the second switch detects the field and raises an alarm.

Elevator and Lift Position

Elevators use reed proximity switches to detect the position of the car and the landing doors, to give levelling signals, and to interlock the doors. The elevator shaft is a harsh environment, full of dust and oil, and reed switches tolerate it well because their contacts are hermetically sealed. Their long life and low cost make them a standard choice for lift position and door detection.

Access Control and Door Monitoring

Beyond intrusion alarms, magnetic door contacts are the standard way to monitor doors in access control systems. They report whether a door is open or closed, how long it has been held open, and whether it has been forced. A door held open too long triggers a warning, and a forced door triggers an alarm, so the same small sensor serves security, safety, and building management at once. Because the contacts are inexpensive and need no power, they can be fitted to every door in a building, giving the access control system complete coverage.

Why Reed and Level Sensing

Reed switches are sealed against dust and moisture, switch without contact and without wear, and need no power to hold a state. They are inexpensive enough to fit on every door and window, and reliable enough to guard them for decades. For security and access control, they are the proven, standard choice.