The TEL TAC has LCD digital readout and “telltale” memory. Compatible with most engines and ignitions, including magnetos and battery powered ignition systems, the tach turns on automatically when the engine is started. Reads RPM in hundreds, from 500 RPM to over 12, 000 RPM on V-8 engines, and to 15, 000 RPM on smaller cylinder engines. After engine is shut off, the highest RPM attained is shown for 30 minutes. All units are powered by a 9-volt alkaline battery which will last for hundreds of hours. Will not work with odd fire V-6, V-4 with Vertex internal coil magneto, or 4-cylinder with EFI.