Many different types of Bluetooth car kits are on the market. Some require a professional installation. Some simply clip to your sun visor. Some use an FM signal so that you can use your car speakers to amplify your calls. Some connect to your stereo through an auxiliary port for the same reason. Regardless of the type of car kit, the primary purpose is the same   a hands-free way of taking calls in your car so that you're not taking your hands off the wheel and your eyes off the road. However, the prices for Bluetooth hands-free car kits swing from $10 to several hundred.

If you only need a Bluetooth car kit for the odd phone call during your commute, then you don't need to spend hundreds of dollars on a high-end model. Instead, you should consider the more affordable Bluetooth FM transmitters and Bluetooth auxiliary adapters.

Bluetooth FM Transmitters

Bluetooth FM transmitters rely solely on an FM signal to amplify the audio instead of having an internal speaker. Your phone connects to the device using Bluetooth, and it converts the audio from your phone to an FM signal. You simply have to find an unused FM station on your stereo and tune the radio to that station. Since you're using your car speakers, the advantage of an FM transmitter is the volume output. You're only limited by your car stereo system. This advantage carries over to streaming music from your phone. Also, most FM transmitters don't have a battery to recharge. Instead, they plug straight into the charging port when in use.

The reason FM transmitters are more affordable than the best Bluetooth car kits is the call quality and hands-free control. FM signals are notoriously inconsistent and unreliable, especially in large cities where FM signals are everywhere. Most FM transmitters lack effective noise and echo cancellation, which leads to muddier conversations. In addition, most FM transmitters lack voice commands and other features, such as text-to-speech and speech-to-text.

Bluetooth Auxiliary Adapters

Auxiliary adapters are Bluetooth hands-free car kits that plug into your car stereo through a 3.5mm auxiliary port. The advantage of a Bluetooth aux adapter is the same as the FM transmitter   your car speakers are the primary audio source. So you can stream calls, music and GPS directions from your phone through your car stereo. However, the auxiliary adapter is better than an FM transmitter because the signal isn't subject to the static and tuning issues that make FM transmissions so inconsistent. The only wireless signal is the Bluetooth connection between your phone and the aux adapter hands-free car kit. As a result, aux adapters are generally more expensive than FM transmitters.

A downside to a hands-free Bluetooth aux kit is its lack of compatibility. Your car stereo must have an auxiliary input on the front; otherwise, it won't be able to use your car speakers. While many car stereos provide an auxiliary port in the front, many still only provide the aux port in the back, where you can't access it without removing the car stereo.

Similar to the FM transmitters, the aux adapters are more affordable than the best Bluetooth car kits because they lack high-end call quality and hands-free control. Most aux adapters use only one microphone, which lacks sufficient internal noise and echo cancellation systems. As a result, your voice competes with all the other noise in your car   the sound of the road, the fan of the air conditioner, other passengers   making it more difficult for your caller to hear you. You'll also hear echoing and feedback, which occurs when the microphone picks up the caller's voice from the car speakers.

FM transmitters and auxiliary adapters work as simple hands-free Bluetooth car kits that allow you to stream music from your phone and to take the odd call while you're on the road. They don't have as many functions as the high-end models, but they give you the essential functions without breaking the bank.

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