Pack of 20 Magnetic door switch

A magnetic door switch (or reed switch) is a sensor used to detect if a door or window is open or closed.
It consists of two main parts: a reed switch inside a housing and a magnet.

Electrical Specifications
Switching Voltage: 12V DC to 24V DC (standard security); up to 110V/220V AC for specialized industrial models.
Switching Current: 0.1A to 0.5A (standard); 
high-power relays handle up to 1A or 2A.
Contact Rating: 3W to 10W (maximum power capacity the internal contacts can safely handle).
Contact Resistance: Less than 100 to 200 milliohms (mΩ)

Main UsesSecurity Systems: Triggers home alarms when windows or doors are breached.
Smart Automation: Turns on lights, pauses HVAC systems, or sends phone notifications.
Access Control: Signals whether commercial gates or emergency doors are securely latched.

How It Works
Door Closed: The magnet sits next to the switch. The magnetic field closes the electrical circuit.
Door Open: The magnet moves away. The circuit breaks, triggering an alarm or turning on a light.