Faria Beede Instruments Kronos 4" Tachometer w/Hourmeter - 7000 RPM Gas - Outboard. 375" (85mm) 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. Benefits: Wide range of scales Multiple signal sources Rugged Reliable construction 7 character LCD display 0-999999.9 Hours Updates in .1 increments Specifications for Faria Beede Instruments Kronos 4" Tachometer w/Hourmeter: Manufacturer: Faria Beede Instruments Color: Black Features of Faria Beede Instruments Kronos 4" Tachometer w/Hourmeter Wide range of scales Available for gas or diesel engines Multiple signal sources Rugged Reliable construction 7 character LCD display Package Contents: Faria Beede Instruments Kronos 4" Tachometer w/Hourmeter Faria Beede Instruments 39040: Kronos 4" Tachometer w/Hourmeter - 7000 RPM Gas - Outboard