Bi-stable / Latching Reed Switches

A latching reed switch is an ideal solution in extremely low power requirements, particularly in battery powered devices. It is also referred to a or bi-stable reed switch. Latching reed switches use two permanent magnets to achieve the latching function. The first magnet is partially magnetized. Bringing the contacts closer together, but they still remain open. The second magnet with an aiding field brought close to the switch will close the contacts.  And they will remain closed until the second magnet is brought close but this time with a reversed magnetic field. So a latching reed switch can exist in either the normally open (N.O.) or normally closed (N.C.) contact state. And the contact state is controlled by reversing the magnetic field of the second magnet.