A dry reed switch is an electronic component that consists of two ferromagnetic reeds sealed within a glass or plastic tube. The reeds are coated with a thin layer of noble metal, such as rhodium, to improve their conductivity. When a magnetic field is applied to the switch, the reeds attract and make contact, completing an electrical circuit. Dry reed switches are commonly used in a variety of electronic applications, such as in automotive sensors, security systems, and industrial controls. They are also used in proximity sensors, where they can be used to detect the presence of magnetic objects or measure magnetic fields.