Here’s an interesting introduction to Reed Relays, Mercury Displacement Relays, Contactors, Polar Relays, Latching Relays, T-Bar Relays, Time Delay Relays, and Stepping Relays. Here’s an interesting ...

Latching relays change their states when you apply a short voltage pulse to their coils. Because these relays require no continuous coil currents to keep their states, you can save considerable power ...