The main objectives of public address and warning system are as follows:

• informational (usual announcements in warning mode, both manual and automatic as well as advertising messages);
• entertainment (transmission of background music, entertainment programs);
• alert and evacuation (emergency messages and appeal of leaders for actions, for example, warnings about fire);
• uninterrupted round-the-clock functioning.

Public address and alert systems are divided into two types: sound warning systems at different objects of business, culture, health care, sport, etc. Sound and warning systems are called Commercial Audio and Public Address.

Commercial Audio - are systems for scoring various types of local facilities and activities (small shops, cafes, restaurants, conference rooms, classrooms, meeting rooms, assembly halls, etc.).

Public Address - are systems of background and voice translating as well as emergency and fire alarm systems (superstores, educational institutions, business centers, hotels, resorts, sanatoriums and other places with lots of apartments and large total area).

The first type of systems can be characterized by local placement of sound amplifying equipment and musical speakers within a single room. They are designated for scoring of different kinds of events. This may be a background sound in restaurants, cafes, small shops, playback and sound reinforcement in the course of school training, during conferences and meetings, in boardrooms, during reports, presentations, performances and other events.

Simple system of this kind one can build on the basis of conventional low-impedance stereo power amplifiers and Hi-Fi loudspeakers. However, the number of column loudspeakers (loudspeakers) in such systems (and thus the gage of the system) will be limited. Stereo amplifier can be connected at best with four loudspeakers, provided that their output impedance proper coordinated. The main disadvantage of this method is the fact that loudspeakers must be connected to each output port with a separate wire, i.e. the possibility of connecting of all columns in parallel with each other is not possible, that lead to the increase of cable lines number. One more disadvantage of such sound system is limit on the length of acoustic cables leading from amplifier to loudspeakers, as well as high requirements to the quality of cables. This is because low impedance output signal of Hi-Fi power amplifier has small amplitude and its signal parameters strongly depend on the length and quality of cable lines, in which it is distributed, that increases overall cost of the system.

More correct and efficient way of building a sound system, even a small in scale, based on the usage of transmitting equipment (amplifiers, loud-speakers, volume regulators) operating at signal levels of 70 -100 V which is specifically designed for uninterrupted all day long operation. In such a system the audio signal is converted into a 100 V format, i.e. increases the amplitude of the signal, which ensures its spread over long distances without loss of efficiency and without usage of expensive acoustic cable. In translational systems loud-speakers (speakers) are connected to each other in parallel (two wire single line), except for systems with more than one scoring zone. In this case loud-speakers must be grouped in zones that will determine the number of cable lines leading to amplifying equipment. However, translation sound systems for 2 and more zones are classified as Public Address systems.

The second type is Public Address System which is designed to provide background music and speech sound in a wide range of facilities and open public access areas: supermarkets, recreation centers, hotels, offices, banks, schools, shopping areas, railway stations, airports , etc. Another important purpose of such systems is an emergency voice notification in case of fire or any other emergency, which is a standard requirement for sound systems in areas with large number of people concentration. In emergency situation may occur panic and people may forget or just not know how to leave a dangerous place. In such a case much greater effect will do calm and confident voice of an operator telling about actions needed in such situation. This system operates automatically: emergency message will be sent with absolute priority to all areas of alert. The widest range of equipment allows you to build warning and translation systems of any configuration and complexity. Scoring system configuration depends on demands applied to it that determine the number and type of sources of music and speech, the number of audio zones, availability of local (zonal) sound level control, priorities of music and speech sources, etc. There are various options of sound systems installation that can be selected in each specific case. This may be a ceiling installation of speakers, wall mounting, in-wall mounting, etc.