The reed switch is a type of electromechanical switch that operates through the principle of magnetism. Professor Valentin Kovalenkov invented it in 1922 at the Petrograd Electrotechnical University (PEU). Walter B. Ellwood developed it into the reed relay in 1936 at Bell Telephone Laboratories. Generally, these switches include a set of ferromagnetic flexible metal contacts, which seal hermetically in a glass envelope. Typically, a magnetic field keeps these contacts open; otherwise, they close … [Read more...]