[Switch type]:N.C. means Normally Closed: When the magnet together, the circuit is conductive( light on ); when the magnet separates, the circuit is not conductive ( light off ).
[materials]: The magnetic switch alarm is with durable zinc alloy housing for better rust resistance.
[applicable scene]:The Rolling Door Contact is designed for use with window and door alarm systems, such as garage, industrial warehouse and shops, etc.