A public address system, abbreviated PA system, is an electronic amplification system used as a communication system in public areas. It is an amplification setup with an amplifier and loudspeakers, used to reinforce a given sound (e.g., a person making a speech, prerecorded music, or a live musical performance) so that the audience can hear it clearly. The PA system is controlled from a mixer which blends the incoming signals from microphones and musical instruments, modifies the tone, and controls the overall level of the signal that is sent to the

amplifier.

The term "PA system" refers to an audio transmission system used in institutional and commercial buildings, in which input from a microphone or prerecorded music is amplified and sent to speakers throughout the building. These types of PA systems are commonly seen in schools (used to read announcements and summon students) and hospitals (used to summon staff or declare states of emergency). Other examples include airports, airplanes, and drive-through windows at fast food chains. Some systems can address specific rooms and exclude others. Other types of PA systems, called intercom systems, also have microphones in each room so that the occupants can reply to the central office