What is an FM transmitter?

An FM transmitter is a portable device that plugs into the headphone jack or other output port of a portable audio or video device, such as an iPod (and other MP3 players), CD players, and satellite radio systems. The sound is then broadcast through the transmitter, and plays through an FM frequency so that music can be played from a device through a car stereo, or any radio without an audio input jack.

FM transmitters are usually battery driven, but some use the cigarette lighter socket in cars, or draw their power from the device itself. They are typically used with portable audio devices such as MP3 or CD players, but can also be used to broadcast other outputs (such as that from a computer sound card) throughout a home or other building.

The FM transmitter plugs into the audio output of audio devices and converts this output into an FM radio signal, which can then be picked up by your car or portable radios. Most devices on the market typically have a short range and can broadcast on any FM frequency from 87.9 to 107.9 MHz (or 76.0 to 108.0 outside the US). Some lower-cost transmitters can only broadcast on the educational band (87.7-91.9), or other limited range frequency.