Reed relay

A reed relay is a relay used to switch a circuit and integrates a reed contact. The reed contacts (reeds) are hermetically sealed in a glass tube which is either evacuated, creating a vacuum, or filled with a protective gas. They also double as the contact spring and magnet armature.

The contact is actuated by an external magnetic field produced by a nearby permanent magnet (reed contact) or generated electrically in an accompanying magnet coil (reed relay). The magnetic field causes the reeds to attract each other, thereby closing the circuit. As soon as the magnetic field is gone or diminishes beyond a certain point, the contact opens again due to the spring effect.