Reed Switch

reed switch
how reed switch works

A graphic illustrating a reed switch. The circuit symbol and a simple diagram representing the construction of the switch are shown and labelled.

An interactive animation demonstrating how a reed switch works. Dragging the magnet near the reed switch to close the connection. Dragging the magnet away from the reed switch to open the switch.

The reed switch is an electrical switch operated by an applied magnetic field. It was invented at Bell Telephone Laboratories in 1936 by W. B. Ellwood. It consists of a pair of contacts on ferrous metal reeds in a hermetically sealed glass envelope. The contacts may be normally open, closing when a magnetic field is present, or normally closed and opening when a magnetic field is applied. The switch may be actuated by a coil, making a reed relay, or by bringing a magnet near to the switch. Once the magnet is pulled away from the switch, the reed switch will go back to its original position.


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