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Dual LEDs can be used for 3 aspect signalling on searchlight heads but the quality of the yellow is only approximate. In this circuit one of the digital I.C.'s sections is used as an oscilator to quickly change between red and green. This gives a sort of orangy yellow output. Red over-rides green and yellow. The period and ratio of the oscilator can be changed to get a more realistic yellow output on some dual LEDs.
Dual LEDs can be used for 3 aspect signalling on searchlight heads but the quality of the yellow is only approximate. In this circuit one of the digital I.C.'s sections is used as an oscilator to quickly change between red and green. This gives a sort of orangy yellow output. Red over-rides green and yellow. The period and ratio of the oscilator can be changed to get a more realistic yellow output on some dual LEDs.
LINK TO IMAGE - sig-3a-sl.gif
Circuit Schematic
