Normally closed
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In electronics, a normally closed switch is one that normally allows current to flow and which prevents current flow when it is perturbed.
- Think of a flashlight/torch: You put a rubber band on its switch so that the flashlight/torch is lit all the time unless you keep holding the switch, against the force of the rubber band, in the open position. The switch is then normally closed.
See also Relay
A switch that is "closed" conducts electricity. Normally closed switches are often spring loaded. The "normal" position of the switch defines its position when it is not being pressed, that is, the position to which it is forced by the action of the spring.
A normally closed switch, thus, is one that is spring loaded and conducts electricity when it is not being pressed. Pressing the switch stops the flow of electricity.
