The diagram below is the relay driver circuit with Snap Acting for the clean switching of the relay. When the input signal at the base of T1 decreases, it turns off allowing T2 to conduct by giving ...

It has 2 terminals and 4 connectors and you can look at the DPDT relay as the equivalent of 2 Single Pole Double Throw SPDT relays. DPDT relay applications 1. Change motor direction with DPDT relay.

The diagrams and photos show how to wire up the fuel pump and oil-pressure switch to a commonly available, industry standard, ISO-type "1 Form C single pole/double throw" (SPDT) relay.