As was the case with the normally closed sensor, a magnet is mounted and centered over the contacts for the latching sensor as well. In this case however, the magnet’s strength is not strong enough to close the contacts. A second magnet is mounted to a moving element where its distance is being sensed. When this second magnet enters the reed switch’s sphere of magnetic influence, the contacts will close. This second magnet’s magnetic strength will be aiding the field of the first magnet. Now when the user removes the second magnet, the contacts will remain in their closed state. This occurs because of the natural wide hysteresis of the reed switch.To have the contacts open again requires a third magnet with opposite polarity to the second magnet that was used. Also, one can use the second magnet with its polarity reversed if that is a feasible option for a given application. When this magnet enters the reed switch’s sphere of magnetic influence, the contacts will open. Removing this magnet, the contacts will remain open completing the cycle. This is ideal for applications where the reed sensor will be in one or the other state for long periods of time. In either state the sensor will draw zero power for each latching operation.