Spun Silver 4 Tachometer wHourmeter 6000 RPM Gas InboardPerimeter-lighted Silver dial with bold Black graphics, polished stainless steel bezel, contoured Black pointer, and domed glass lens.Electronic tachometers work by counting pulses generated by the ingition system, alternator, tach signal generator or magnetic pickup sender. The tach is hooked up to 12VDC, Ground and one of the signal sources listed above.By selecting the right tach and setting the switch on the back to the correct postion