Originally Posted by CBRich

A diode keeps the current from bleeding back to the other side. Otherwise activating the toggle switch turn on the brake and reverse lights. There is no resistor, it is a 5 pin relay. This allows the setup to default to a solid non blinking form until reverse is activated. At that point the current from the reverse lights throws the switch inside the relay directing the current toward the flash. The results is that by default the toggle switch and brake lights activate a solid light while reverse throws the switch resulting in a blinking light.

Flashingbrakelights.com has a nice module which will blink six times and then stay solid upon braking. If this is all you need you can purchase from them. In addition to what they have I am also wanting to add external control for a solid fog and blinking in reverse, not just six times but until I am no longer in reverse.