The reed switch is an electrical switch operated by an applied magnetic field. It contains a pair (or more) of magnetizable, flexible, metal reeds whose end portions are separated by a small gap. The reeds are hermetically sealed in opposite ends of a tubular glass envelope. The two ferrous materials inside the switch pull together when exposed to a magnetic field and hence completing the circuit. When the magnetic field is removed, the reeds separate and the switch opens. This makes for a great non-contact switch. These switches are designed with a high degree of reliability. The ferrous metal contacts are sealed in an environment at a predetermined pressure or vacuum, specifically chosen for their intended areas of application. Various manufacturers provides application specific reed switches that can be used in low temperature environments. Reed switches can be used as an effective passive safety system suited to alert driver. With the evolution of inte...