Seco-Larm SL-SM300QW Normally Open Door Switch, 5PK

Seco LarmSKU: SL-SM300QW-5PK



SecoLarm SL-SM300QW Normally Open Door Switch, Package of 5

Normally Open Door Switch

This Normally Open Proximity Door Switch SL-SM300QW is built to monitor the opening and closing state of your windows and doors. These are traditionally used with a security system or automation system. The functioning internal reed switch closes and the circuit is completed when doors and windows OPEN.

These are meant for contact closure rather and are not meant to run lights. A supplementary relay and surge suppressioin must be used if the intention of the switch is to activate a bell or siren strobe or a voltage load.

Normally Closed vs Normally Open


Normally open *Example: light turns on when door is open

A N/O contact does not flow current in its normal state. Activating the contact (opening a door/window) will create a flow of current to create an alarm/turn on light etc.

Normally closed *Example: light is on when door is closed

A N/C contact flows current in its normal state. Activating the contact (opening a window/door) will interrupt the contact, allowing no current to flow. Normally closed is typically used for alarm systems to alert when door/window is opened or wire is cut.

Door Switch Specifications:

  • Dimensions: 2.5" x 0.75" x 0.5" (part with screw terminals)2.5" x 0.75" x 0.625" (part with magnet)
  • Contacts: Closed when Door is Open and Open when Door is Closed

Door Switch Includes:

  • 5 x - Magnetic Reed Door Switch Kit

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