Reed switches consist of reed-like contacts of magnetic material which are brought together by the proximity of a magnetic field. A permanent magnet or an electromagnet, or combination of the two can be used. These switches are hermetically sealed and, therefore moisture and dust proof. When used with a permanent magnet, Reed switches operate as a mechanical switch or with a suitable coil as a sensitive relay. Several switches may be used together with a single magnet to assemble a special rotary switch. Reed switches may be used to control low power lamps, transistors or other components.