A double-pole switch is used to control two separate circuits at the same time from the same switch. Power panels use double-pole breaker switches for 240-volt circuits. A residential 240-volt circuit is actually two 120-volt circuits that share the common white wire. A double-pole switch allows the power to be cut off from both circuits at the same time. This helps increase safety when working on these types of circuits.
Identify the four terminals on the double-pole switch. The two terminals connected to the knife leaver should be labelled L1 and L2. The two terminals not connected to the leaver should be called C1 and C2. When the leaver is closed, L1 should connect to C1 and L2 should contact C2.
Connect L1 to the negative side of battery one. Connect L2 to the negative side of battery two. Connect the positive side of battery one to one of the terminals on light bulb one. Connect the positive side of battery two to one of the terminals on light bulb two.
Connect the remaining terminal of light bulb one to terminal C1. Connect the remaining terminal of light bulb two to terminal C2. When the switch is thrown, both lights will light up.