This circuit looks relatively simple at first sight but it is nevertheless quite versatile. It can be configured to provide a flashing or dimming function and only needs two connections to wire it in series with a 12 V load or lamp.
 
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A while back the author found a circuit ‘Somewhere on the Net’ for a flashing turn indicator circuit that was wired in series with the load lamp. It was just what he was after; normal lamp flasher circuits have at least three connections (Supply, ground and output). He studied the circuit, made some improvements and came up with this design which can be easily incorporated into existing vehicle wiring without the need for extra cabling. The circuit can be used to replace a broken hotwire flasher unit used in the turn-indicator circuit of a vintage car (wired in series with the lamp).