35chev,
When you have two taillights and you are stopped, making a left turn, the right brake light shines steady bright for a stop and the left brake light blinks bright for the left turn.
As Waldo says, this all happens in the turn signal mechanism before zooming down the wires to the back of the truck. Three wires gets the whole thing done. One wire for BOTH taillights and license plate light, and ONE WIRE EACH for a left brake light and a right brake light.
Stuart
