Review on 🔊 APIELE 16mm 12V Momentary Speaker Horn Push Button Toggle Switch - 0.63" Mounting Hole - 1NO 1NC SPDT - Pre-Wiring Socket - Car Auto Motor - Black Shell (Green, Black Shell) by Kevin Henry

Very cool looking knob and works well once you figure out the wiring for your specific application. And to confuse it even more, the green wire is where the yellow wire should be and vice versa. Thank you to the other reviewers who shared their experiences, a huge help. Black is lapped to the frame, Blue is normally open (NO), Green is normally closed (NC) (presumably yellow per manufacturer's instructions), Yellow connects to 12v from a battery or ignition that supplies 12v (according to manufacturer's instructions it should be the green wire). Red is connected to 12V to power the LED in the button. My unit is a horn so I connected the blue wire to my positive wire that goes to the horn compressor. The only other wire going to the compressor is chassis ground. The blue wire circuit (on the LED button) is normally open until I press the button and close the circuit or close the circuit, at which point the beep sounds. I didn't use the normally closed green wire at all. Much luck