Truck marker light

Claim 1

A marker light for trucks, semi-trailers and the like having electrical systems with either positive or negative ground comprising a base having means for mounting the same on a truck, a lens mounted on the base, lamp means having first and second filaments, lamp supporting means, means for mounting the lamp supporting means on the base, said lamp supporting means having means for receiving said lamp means, a ground terminal adapted to be connected to the truck electrical system ground, a power terminal adapted to be connected to the live terminal of the truck electrical system, a first transistor, a second transistor, a full wave bridge rectifier having its input connected across said power and ground terminals and having its output connected in series through the base and emitter of said first transistor to the first filament and also having its output connected in series through the collector and emitter of said second transistor to the second filament, a connection from the collector of the first transistor to the base of the second transistor for biasing the second transistor off only while the first transistor is on and current is flowing throught the first transistor as would be the case when the first filament is unbroken, and a bias resistor connected to the base of the second transistor for biasing said second transistor on, the bias from said resistor being overcome by the bias from said first transistor when said first transistor is on and conducting current through the first filament.