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magnetic home security switch
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Type of magnetic switch for window sensor – normally closed or normally open?

Installing new vinyl home windows, current wood windows use the recessed switches, however I think when they pull out old window – we have to go with the surface mount magnetic contact switches. I’m confused with the normally closed vs normally open. I believe I want normally closed configuration, but some products out there are confusing – for ex. no for nc configuration
Help? Need someone who specializes in electronics or home security

Both types are used in the alarm industry. Normally open or normally closed refers to the switch contact position when the switch is at rest, i.e. plunger not pushed or magnetic switch nowhere near a magnet. Closed means that the switch contacts are connected.

Normally closed are the more common plunger type and normally open are the more common magnetic type. To avoid extensive rewiring you’ll want to stick with the same type.

Once you pull one of the existing switches you can check it for continuity with the plunger pushed in and at rest to determine what you have.

As an example that is easier to visualize, the light switch in a refrigerator is a normally closed type even though it is usually open when the door is closed.

Don

magnetic home security switch