A circuit for interfacing between a conventional traffic signal's control monitor and a plurality of light emitting diodes (LEDs) replacing an incandescent lamp of the traffic signal is disclosed. The interface circuit includes a current source for driving the LEDs with a regulated power factor corrected...http://www.google.se/patents/US6150771?utm_source=gb-gplus-sharePatent US6150771 - Circuit for interfacing between a conventional traffic signal conflict monitor and light emitting diodes replacing a conventional incandescent bulb in the signal
