Faria Beede Instruments Tachometer w/Digital Hourmeter 6000 RPM Gas Inboard Chesapeake Black w/Stainless Steel 5". 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 hte signal sources listed above.By selecting the right tach and setting the switch on the back to the correct postion you let the tachometer know how many pulses are sent per each engine revolution. Specifications for Faria Beede Instruments 5" Tachometer w/Digital Hourmeter 6000 RPM Gas Inboard Chesapeake Black w/Stainless Steel: Manufacturer: Faria Beede Instruments Color: Silver Features of Faria Beede Instruments 5" Tachometer w/Digital Hourmeter 6000 RPM Gas Inboard Chesapeake Black w/Stainless Steel Wide range of scales Available for gas or diesel engines Multiple signal sources Anti-scratch glass lens Plastic Cases for corrosion resistance and long life Chesapeake Black with Stainless Steel Package Contents: Faria Beede Instruments 5" Tachometer w/Digital Hourmeter 6000 RPM Gas Inboard Chesapeake Black w/Stainless Steel Faria Beede Instruments 33763: Tachometer w/Digital Hourmeter 6000 RPM Gas Inboard Chesapeake Black w/Stainless Steel 5"