ENM’s PT18 Series is a self-powered engine digital tach/maintenance/hour meter with a replaceable battery. The PT18 keeps track of true engine rpm and running time for all types of gasoline engines. The unit is powered by an internal lithium battery; no external power connections are required. The operation of the tach/hour meter is triggered by approximately 5-foot shielded and external lead, wrapped around the spark plug wire of the engine. Since the unit is triggered by the spark of the engine, the hours and the rpm display actual operation. This is useful for maintenance and warranty applications for any type of engine-powered machinery. When the engine is on, the display will read the rpm of the engine. When the engine is off, the display will switch to run time and remain visible. For more information, visit www.enmco.com.