SPST reed contact switches use one circuit that opens or closes when the magnet moves, making them a straightforward choice for monitoring doors, windows, gates, and other openings. SPDT reed contact switches provide a common terminal plus normally open and normally closed contacts, giving installers more wiring options for alarm zones, status monitoring, or applications that need a changeover signal.

Compare the specified operating or standard gap, which is the distance between the contact and magnet when the door, window, gate, or overhead door is closed, and choose a switch with enough allowance for the installation. Product options in this assortment range from about one-half inch for a recessed contact in steel to one inch or more for surface-mount contacts, with an overhead-door contact rated for a 2 3/8-inch minimum gap, so also check the closed gap, departure gap, mounting surface, and alignment.

Choose a wired reed contact switch when the door or window is accessible for cable installation and the security panel has an available wired zone, such as with surface-mount, recessed, or press-fit applications. Choose a wireless model when running cable would add installation work or when monitoring locations such as gates, outdoor doors, or remote openings requires a wireless connection.

When installing reed contact switches indoors, match the form factor to the opening, such as surface-mount, recessed, or press-fit, and account for magnet alignment, the required gap, available mounting space, and whether screw terminals, wire leads, or adhesive mounting best fit the job. For outdoor or commercial applications, select a switch designed for wider gaps, changing temperatures, moisture or impact exposure, and high-traffic conditions, then confirm that its wired or wireless signaling method works with the security system.