Abstract: A hands-free adapter for interfacing a mobile phone handset with an existing audio system attaches to the handset by means of the accessory connectors that are generally located on the bottom or back of the handset. The adapter modulates the received audio from an in-coming call with a pre-selected FM or AM carrier frequency, and broadcasts the resulting, low power signal to the antenna of a receiver of the existing audio system, which may include a home stereo system, a portable stereo system, or a vehicle radio. The receiver is tuned to the carrier frequency used by the adapter so that the in-coming audio from the mobile phone can be heard over the audio system speakers. For Radio Data System (RDS)-capable radio receivers, a processor is provided within the adapter to generate channel data, which is then transmitted with the carrier signal. The RDS-capable radio receives the RDS signal and automatically tunes itself to the selected channel.