B4 is a Bluetooth FM Transmitter for your car. It gives you a possibility to answer or make phone calls hands-free. A2DP technology, supported by B4, allows you to listen to high-quality stereo music wirelessly. The signals are received from your mobile phone and reproduced by the stereo system in your car. The B4 supports only mobile phones and handhelds, but you can connect your iPod or MP3 player onto this gadget via 3.5mm input jack. This FM transmitter requires no charging because it uses power from the power adapter (aka cigarette lighter) of your car. The connection between the B4 itself and its part that you put into the power adapter is flexible, so you can find a viewing angle that is best for you.

This is my first review of a car A2DP device. I tested it with the Palm Treo 680 (with Audio Gateway installed), ETen M600+ (in-built A2DP) and with my Samsung SGH-E530 (with no A2DP, just for calls).

Starting the tests, I bravely forgot the Manual at home so I had to rely on my intuition. No way! The passkey turned out to be not the usual 0000, but 9999 (as I found out from the manual later). So next time I studied the User guide and started my tests. In fact, the pairing couldn't be easier. As you put the device into a 12-volt cigarette lighter, it starts flashing blue and green at once. These colors indicate that the transmitter is in pairing mode, and now you can enable Bluetooth function within your mobile phone and search for Bluetooth devices. Select Carkit and enter these notorious 9999. As the pairing is ready, the transmitter has to chime. By the way, search B4 in “All Bluetooth devices”, because ETen, for instance, wasn't able to find this headset in the Headset category, and “Carkit” was detected as unknown type.

The B4 can remember only the last gadget.

Adjustment. In fact, the operation isn't hard at all, because the device has only three buttons. They are the Function Key (with the picture of a receiver) and two little buttons for choosing the FM station. You can choose any station in the frequency range of 87.7 – 108.0MHz. I live in a big city and it was really hard to find an appropriate station because all the frequencies were occupied. Maybe for this reason we heard some interference sometimes; in the countryside things should be better.

There exist no Volume up/down and Next/Previous track buttons. You can adjust Volume from your car stereo, but in order to change song you have to pull out your phone from your pocket.

The buttons are hard to distinguish in the dark because there is no button lighting. It is not a big deal, but sometimes it bothers.

Display. There is a display that helps to pair and connect the device. In the Search Mode the display blinks blue and green, in the Connect Mode there has to be solid blue light, according to the manual. But in my case there is a solid blue light if the Transmitter is idle, I mean it doesn't see a mobile phone and isn't able to play music. And all the time the music is being played the display blinks green and blue. I've read in people's comments that it is a common thing and that users are annoyed by this flashing. As for me, I really don't pay attention to it.

Calls. You can listen to music and receive calls. After the call is ended the music resumes (as it was in my case). But some mobile phones may require you to press Play on your phone to start music again.

During phone conversations I was not heard well. But I can't state which fault was that, since the power adapter of my car is situated low and the mic is much farther from my mouth. In many cars the lighter is situated nearer to a speaking person, but users in their reviews complain about the necessity of shouting to people anyway. On the other hand, when my friend was speaking via B4 in the car and I talked via my mobile phone outside the car, I could hear him well without his screaming. But there were a lot of hoarseness and creaks.

When I was sitting in my car and speaking via B4, I heard the voice clearly, but noticed echo and unpleasant background noise. My friend heard me clearly too, though I had to speak louder.

Well, the Transmitter is not intended for endless conversations. You’d better keep a wary eye on the road.

Sound. I refused to listen to music with ETen. The sound quality really leaves much to be desired... I even wasn't sure the sound was transmitted via A2DP and not via Handsfree. There definitely was no stereo. I tried to search the confirmation of this fact in ETen settings, but in this handheld there were no clear data what profile is used during sound transmission.

As for A2DP in Treo 680, I have almost no complaints. Maybe some skipping just several times occured, but it depended on bitrate.

Compared to other FM Transmitters (for example, iRiver's), the quality of sound that depends on the radio waves is ten times better. In iRiver there was a great distortion and interference of other stations, street railway and trolleybus wires.

What do we have?

Basses are transmitted on an average level.

Instruments without human voice sound really cool. With voice the track sounds worse to some degree.

Classical music sounds perfectly! I enjoyed Vivaldi most of all. Sometimes I even forgot that I was listening to music via FM Transmitter.

Those who are too fastidious about sound quality of songs may listen to audiobooks, this doesn't require super quality of sound transmission.

Conclusion. I have to say that all the bad points I admitted are present in every device of such type in a varying degree. The situation is complicated by the presence of not only A2DP, but FM factor as well. I just tried to mention everything that can upset you in such devices. In spite of some disadvantages, FM Transmitter is a very handy thing. Especially it is great for those who don't want to upgrade their car stereo (moreover, there is not always a possibility to change car stereo due to guarantee issues, driving a company car, e.g.), but want to get a handsfree and listen to music from a different device – no matter be it via A2DP or 3.5mm jack, - both ways have their advantages.

If you listen to audiobooks or podcasts, you need to go on from the place where you stopped last time. That's why the audio source has to be the same. With B4 you can easily enjoy the continuation of your book in the car.

B4 is obviously worth buying, especially if you spend  in your car a lot of your precious time.

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