This circuit allows an SPST momentary pushbutton to act as a push-on push-off switch, using a DPDT latching (bi-stable) relay. It was originally intended to allow a single pushbutton switch on the ...

The relay's primary appeal is its ability to do a lesser-switch's bidding but it's capable of so much more. Relays can be wired together to create very useful, simple, and utterly reliable networks.