The NAV-TV MOST-AUX AUDI is a M.O.S.T. fiber optic interface that introduces audio into select fiber-equipped Audi vehicles with no degradation in sound quality. AUX audio is triggered with an external toggle switch (not included). Unlike cheap FM-based modules that transmit sound via an FM station, the MOST-AUX interfaces directly into the OEM fiber system and is designed to work specifically with a compatibile Audi vehicle.