Apple's iPhone smartphone comes with an iPod app pre-installed, making the device a personal audio player as well a phone. Users can listen to music stored on their iPhone through the device's speakers or the supplied earbuds, or they can connect their iPhone to an external set of speakers for amplified listening. If you want to play an iPhone's music through your car speakers, you have a number of options at your disposal.
If your car stereo has an auxiliary line-in port, you can connect your iPhone directly to your car stereo and output the music stored on your iPhone through your car speakers. To do so, simply connect a 3.5 mm auxiliary cord from the headphone jack on the iPhone to the car stereo's auxiliary port, press the "AUX" button on the car stereo and begin playing the music on the iPhone. With the car stereo set to the "AUX" mode, the music will automatically begin playing through the car's speakers.
Cassette Tape Adapter
If your car has a tape deck, you can play music through your car speakers through the use of a cassette tape adapter. To do so, plug the 3.5 mm connector into the iPhone's headphone jack and insert the cassette end of the adapter into the car's cassette player. Set the car stereo to "Tape" or "Cassette" mode and press the "Play" button on the tape deck. Begin playing the music on the iPhone and the music will automatically be output through the car's speakers.
An FM transmitter works with any car that has an FM stereo. To use an FM transmitter, plug the device into the USB connector on the bottom of the iPhone and, if necessary, plug the power adapter into the car's cigarette lighter or power port. Tune the FM transmitter to a frequency with a small amount of interference and tune the car's FM stereo to the same frequency. Begin playing the music on the iPhone and the music will be output through the car's stereo on the specified FM channel.
AirPlay and the PhotoFast AP1000
With iOS 4.0, Apple brought the AirPlay feature to the iPhone. This feature allows iPhone owners to wirelessly stream the music stored on their iPhone to AirPlay-compatible speakers. As of March 2011, there are no car stereos that come with AirPlay functionality. PhotoFast, however, manufactures a device that can make any car stereo AirPlay-compatible, allowing the stereo to pick-up the iPhone's AirPlay signal so that you can simply tap the AirPlay icon on the iPhone screen to stream the music stored on your iPhone and output the music through the car's speakers.
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