A public address system (PA system) is an electronic sound amplification and distribution system with a microphone, amplifier and loud speakers, used to allow a person to address a large public, for example for announcements of movements at large and noisy air and rail terminals.
The system can transmit alarm tone and routine voice messages, from a central location, to all or selected areas of the facility, in a reliable and safe manner, by the use of loudspeakers.
- Educational Institutions and Offices – These are not used all the time, but are used when a special announcement has to be made into the classrooms. Each classroom has a speaker of its own, and the source is from a designated room within the institution. A very low wattage is required to operate this public system. A similar system is found in offices.
- Railway Stations and Similar Public Places – Public address systems are widely used in making announcements to large groups of people such as those assembled on a railway station or an airport. These speakers are fairly powerful, because they have to carry the sound over the accumulated noises of several thousands of people.
- Concerts – Concerts cannot work without a good capacity public address system. These are the most sophisticated types, because the success of the concert will mightily depend on the quality of sound that is carried over to the audience. Professional people handle these systems. Indoor concerts will require thousands of watts of speakers, but outdoor concerts will require anything above 10,000 watts.
There are hundreds of other places where such systems are used, but these three give a fair indication of the manner they are put to use – for warnings, instructions, explanations and even for entertainment.