You can make a XOR with only one relay, depending on how you wire the two coil signals, ... I’ve had in making my own relays (for use in computing circuits) with the help of a 3D printer.

A solution to arching is removing gases that ionize from the contact area. This implies that high-voltage switching works well in a vacuum. In a vacuum of 10-6 millimeters of mercury, for example, ...

An RC circuit in series with the coil allows full-current turn-on for reliable relay operation, then reduces the current to save power. Fellow engineer Sanjay R. Chendvankar of Mumbai, India ...

By creating a virtual configurable critical load panel for each backup power source, available power can be maximized by sending it to only a few priority circuits until the utility power is restored.

Tiny Circuit Saves Big On Relay Power March 16, 2006 Designers frequently use special circuits to reduce the power required to hold a relay in the latched position.