MSD SIGNAL CHANNEL DIGITAL IGNITION TESTER -- Includes a load-producing clip-on spark plug; Features an LCD display for RPM; Easily tests an MSD 6-, 7-, or 8-series ignition control; Tests the ignition and coil operation, RPM limits, and shift lights; Operates on 4-, 6-, or 8-cylinder engines and simulates up to 16000 RPM.