Comparison Kenwood KMM-BT309 vs Kenwood KMM-BT209

The number of line outputs (see above) provided in the design of the radio. It should be noted that usually these outputs use RCA connectors (“tulip”), and the analog format allows only one audio channel to be transmitted through one such. Therefore, to work with a stereo signal, two RCA connectors are required, and just a pair of such jacks is considered to be one line output - a set designed for one set of stereo speakers. The main difference between this interface and the same RCA used to connect speakers (see above) is that the line output receives a signal from a preamplifier that is unsuitable for feeding to passive acoustics. Such a signal must be sent to active speakers or an external amplifier (whereas the speaker is connected to the output of a power amplifier designed for passive speakers).

The ability to choose the backlight colour for the control panel, and sometimes also for the radio display. The specific range of shades available can vary, whether it be a few colours or the entire RGB palette; see "Illumination colour" for details. Anyway, this feature does not play a functional role, however, it allows you to customize the appearance of the device so that it is in harmony with the appearance of the dashboard and matches the user's mood.

The colour of the backlight plays primarily an aesthetic role, allowing you to choose a radio for the design of the dashboard and user preferences. In addition, some colours have a practical meaning. So, the red backlight is extremely popular nowadays also because it is almost perfect for the dark time of the day: this shade does not knock down "night vision" and has a stimulating effect on the nervous system. And green, on the contrary, relieves excessive nervousness and promotes peace of mind. Other popular colours in modern times include white, blue, orange, yellow, purple ; they do not have such pronounced effects, here the main selection criterion is “like or dislike”.

Also note that in many models several backlight colours are indicated at once. This means that the device has a backlight with adjustable colour selection. At the same time, there are models with a choice of a full range of RGB colours.