When power is applied to the reed relay coil, the magnetic field produced must be at least equal and opposite in polarity of the magnet. The oppositely polarized magnetic field produced by the coil will open the contacts. Removing the coil power will cause the contacts to automatically reclose. This completes the cycle of how a normally closed reed relay works. What is so effective about a normally closed reed relay is that the relay will draw no power for applications calling for the contacts to be closed for long periods of time. A latching reed relay is accomplished in a similar way but generally uses two coils. The first coil closes the contacts and the second coil opens the contacts.