Reed switch

Assignment

To react to the change in low currents or to the movement of permanent magnets.

Function

Two or, depending on the type of circuit, also three contact reeds are melted into a small glass tube in which a vacuum exists, or which is filled with protective gas. These reeds are magnetised and react very sensitively to the field-lines of a permanent magnet or an electric field.
If current carrying wire is wound around a reed contact, the contact can, for example, control the function of rear lights or indicator lamps. Other applications, with a higher switching frequency, e.g., an RPM measurement, are also possible. Due to the protection of the contacts, the service life is almost unlimited.