thumb|right|258px|(from top) Single-pole reed switch, four-pole reed switch and single-pole reed relay. Scale in centimeters.
thumb|258px|Reed switch, contact detail.
thumb|258px|Commonly-used circuit symbol
thumb|258px|Operation of the reed switch
The reed switch is an electromechanical switch operated by an applied magnetic field. It was invented in 1922 by professor Valentin Kovalenkov at the Petrograd Electrotechnical University,
Description
thumb|left|333px|Reed switch diagrams from Walter B. Ellwood's 1941 patent, Reed switches in keyboards have largely been superseded by [[Hall effect sensor|Hall effect switches.
thumb|[[Robik#PKM 1B|PKM 1B (left) next to Cherry MX]]
Electric and electronic pedal keyboards used by pipe organ and Hammond organ players often use reed switches, where the glass enclosure of the contacts protects them from dirt, dust, and other particles. They may also be used to control diving equipment, such as flashlights or cameras, which must be sealed to keep water out under high pressure.
Life
The mechanical motion of the reeds is below the fatigue limit of the materials, so the reeds do not break due to fatigue. Wear and life are almost entirely dependent on the electrical circuit's effect on the contacts along with the properties of the specific reed switch used. Contact surface wear occurs only when the switch contacts open or close. Because of this, manufacturers rate life in number of operations rather than hours or years. In general, higher voltages and higher currents cause faster wear and shorter life. Depending on the electrical load, life can be in the range of thousands of operations or billions of operations.
See also
- List of sensors