A device that enables a digital music player to work through an automobile's audio system. Generic MP3 car adapters work with all players, including iPods; however, there are many car adapters designed for only the iPod (see iPod car adapter).MP3 car adapters plug into the player's headset jack, which outputs analog sound. Such adapters work with not only MP3 players, but with any music source such as a portable CD or tape cassette player, or even a laptop computer.Direct ConnectionsThe best type of MP3 car adapter is a direct connection to the car's audio system. Already existing buttons on the dashboard and steering wheel can be used to control the volume and other sound processing; however, they cannot control the track selection on the player.Many new cars have an auxiliary audio input socket on the dashboard for this purpose, labeled "AUX," "Audio" or "Media." It is also possible to retrofit older cars with direct connections, depending on model; for example, a CD changer port can sometimes be used. After-market stereo and navigation systems typically have an auxiliary input, which is wired to a socket that is mounted on the dashboard.Devious ConnectionsFM transmitters and cassette adapters provide two easy ways to attach a player by pretending to be a radio station and a tape cassette. The FM transmitter, also called an "FM modulator," transmits the audio as an FM radio signal that is picked up by the car's antenna, while the cassette adapter uses a modified tape cassette.