Thanks to increasingly larger internal storage, MP3 players can fit entire libraries of music onto a single device. If you want to use them while driving in a car, though, it can be difficult. Many cars don't feature integrated compatibility between MP3 players and audio systems. However, third-party devices make it possible to listen to your MP3 player in the car.
FM transmitters broadcast a low broadcast signal that can be picked up by a car's radio. When you play music from your MP3 player while it's connected to the transmitter, it turns the device into a local radio station, allowing you to hear and control audio playback through the car's radio. Audio quality is dependent on area radio activity, though--if other stations occupy the same radio frequency, playback quality will be poor.
Many new car stereos feature an auxiliary input jack in the dashboard. When a 3.5 mm audio cable is connected from the dashboard to a device like a MP3 player, audio playback will be routed directly into the car stereo. This provides the best audio playback quality.
Many newer cars feature a 32-pin iPod cable dock integrated directly into the car's dashboard. These are incompatible with all non-iPod MP3 players, but they allow for you to directly play audio through the car's stereo.
Tape Deck Adapters
Cassette tape adapters feature a plastic cassette tape with a 3.5 mm audio cable. When the cassette is loaded into a tape deck with a connected audio source, the adapter indirectly routes music into the car's stereo. These adapters are limited to cars with tape decks, though, and audio playback is around the quality of FM transmitters.
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