A truck fleet has 6 volt and newer 12 volt semi tractors to pull 6 volt light system on semi trailers. So?
Large resistors could lower power from 12 volts to 6 volts for trailor. Or?
Fleet owner added extra battery post to 12 volt batteries to get 6 volts. Top lights are running lamps and stop lights of 12 volt tractor and lower lights are to power 6 volt semi trailer lamps.
Other two voltage systems might work with this system.
