■ Car stereos are characterized by a compact design and developed automation, allowing you to listen to music or other programmes continuously, regardless of changing reception conditions, with minimal driver involvement in the operation of the device. In addition, they can be equipped with a removable front panel, preventing the theft of the device. This equipment is designed to work with two or four speakers. The output power of these devices does not generally exceed 35 In.

■ Speakers are the basic equipment of audio equipment. Speakers work individually or several appropriately selected in the housing, i.e. a loudspeaker. The design of the loudspeaker determines the efficiency of speaker use. The woofer column is constructed differently (Bass), for example. from the so-called. basreflex, i.e. a hole located on the front or back wall of the column, otherwise broadband column (for music playback), still different column on average- and tweeter (for example. for exclusive speech playback).

▲ An important parameter characterizing the usefulness of loudspeakers is the frequency range transmitted by the loudspeaker and the frequency characteristics of the loudspeaker. High-end wideband loudspeakers carry the entire range of sound frequencies perceived by man through the sense of hearing, Ie. 20 – 22000 Hz. Extremely bass speakers transmit sounds on average in the range 20-200 Hz, while columns with an average profile- and tweeter work in the range from above 100 into 20000 Hz. Mid-range speaker system transmits frequencies in the range 50-20000 Hz. The frequency response of the column is given in the form of a graph, illustrating the relationship between the frequency of sound (usually on a logarithmic scale), and its intensity in decibels (Db). It indicates at what volume sounds of different frequencies are emitted. This allows you to determine, whether the loudspeaker is able to meet the requirements set for the equipment.

Another parameter that characterizes loudspeakers is their power. For speaker sets, the most commonly given are the rated power and music power. The rated power is measured by a continuous sine wave signal fed to the set by 100 hours. During this time, the kit cannot be damaged and should work properly. Thanks to the measurement conditions set in this way, rated power describes the heat resistance of the speaker, which means, that providing a continuous signal with more power than the rated one may damage the speaker. Measurement of musical power is made, by bringing a sinusoidal waveform to the speaker in short periods of time (into 2 Seconds) and of this level, so that it does not cause a noticeable increase in reception distortion. The musical power thus determines the behavior of the speaker for impulse waveforms and informs about the characteristics of the speaker's vibrating system. Musical power is generally about 70 – 100% greater than rated power, which means, that a given set can with a high degree of probability transmit faithfully short pulse waveforms with much higher power than the rated. Loudspeakers manufactured for home and studio applications have a rated power not exceeding in general 250 In.

An important parameter of loudspeakers is also their rated impedance (electrical resistance). Can be, depending on the model, 4, 6, 8 or 10 Ω. When choosing a loudspeaker, you should pay attention to this parameter, because the effective use of the speaker system requires, so that the resistance of the column is the same, like the so-called. output resistance (output impedance) Amplifier, characterizing the output, to which the loudspeaker is connected.

Speaker systems may include filters in their housing that allow you to change the frequency characteristics of loudspeakers or speaker sets by limiting the frequency range or cutting a specific frequency band. Some speaker systems may have a built-in control amplifier.

Headphones are divided into headphones (covering the head) and in-ear (inserted individually into the ears). Headphones can also be divided into wired (connected to the equipment by means of a cable) and wireless (working in a wireless infrared transmission system). The volume control and The Mono/Stereo playback switch can be installed on the connecting cable of the headphones.

It is generally accepted, that the human ear receives sounds from 20 Hz to 20 Khz, however, it is difficult to define these boundaries strictly. With age, hearing of the highest frequencies deteriorates. Audio equipment is also not perfect, because not all devices are able to carry the full audible frequency band. FM tuner, working in the field of VHF, transfers bandwidth 10 Hz- 15 Khz (or to 12,5 Khz), cassette recorder, depending on the type of tape, is characterized by a frequency response 20 Hz – 14 Khz, and sometimes to 18 Khz. The best frequency response characterizes the CD player and other digital devices (2 Hzh-20 kHz). Amplifiers usually have a wide frequency response, Most 2 Hz -150 Khz. Only high-end loudspeakers are able to fully cover the audible band, while headphones allow you to get the frequency response even from 2 Hz to 40 Khz.

Using different audio-video devices requires a certain distance between them. Placing them close to each other can have an adverse effect on their operation, for example. proximity to speakers may cause discoloration on the TV screen.