Double Pole Double Throw Relay Symbol. The 2 coil terminals is where the voltage is placed in order to energize the coil. It has one common terminal and 2 contacts. Sp and dp refer to single pole and double pole st and dt refer to single throw and double throw.
Sp switches control only one electrical circuit. Dpdt double pole double throw.
Single pole double throw spdt relay contains two coil terminals and common terminal then two switching terminals n o normally open n c normally close if there is not enough dc supply in.
Sp and dp refer to single pole and double pole st and dt refer to single throw and double throw. The dpdt relay double pole double throw is quite interesting and can be used in various scenarious including for changing the direction of a motor as you can see in the picture below. 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 double pole double throw.
