GMRC-03 Class II data interface for the 1997-2004 Cadillac DeVille, Eldorado and Seville Specifically designed for applicable vehicles noe equipped with OnStar or a factory-amplified system Allows use of factory chime system-chime continues to come from factory front speaker location Supplies 10 amp 12 volt switched power Critical for use when consumer replaces the factory radio, then later replaces aftermarket amplifiers and speakers