A Public Address (PA) system is a collection of audio equipment that allows broadcasts over a designated area. Often found in schools and office buildings, PA systems can be used for general announcements or emergency information, providing a simple way to get information out quickly. PA systems can be basic or advanced, and people can customize them to fit a variety of needs. There are even personal models that can be less expensive, but allow for a much shorter range.
General Systems
Basic PA systems are comprised of loudspeakers placed in convenient locations around a broadcasting area, an amplifier to increase the sound, and a mixer that adjusts audio levels. The user speaks into a microphone, and the sound is transmitted through connected cables, or a wireless system, out through the speakers. Some systems also include microphones or intercoms near the speaker locations, allowing the listener to reply to the central location. These responses are not broadcast to the entire system, however, but only to the main user area.
Functions for Schools
Many schools use a PA system to broadcast daily announcements about school activities, and often let students use it to give reports or announce special events. The device can also function as an emergency warning system. In case of fires, earthquakes or other natural disasters, administrators often use a PA system to instruct students and teachers on where to go and how to respond. With the tragic rise in school shootings in the early 21st Century, many schools have installed special emergency warnings through these systems to alert students and staff about a violent attack on the campus.
Performance Systems
Many venues use a large-scale PA system to amplify sound for concerts or theater productions. Often called Sound Reinforcement (SR) systems, these versions are much more complex than the simple ones found in schools and offices. SR systems frequently use a dual broadcast setup, projecting the sound from the stage into the audience, and also into backstage monitors that keep any off-stage personnel informed of what is happening. This type of PA system may have dozens of microphones feeding into it, and may need several technicians to operate and maintain it correctly.
Personal Units and Custom Devices
While a simple and portable PA system is often fairly expensive, it can provide a speaker with some options for addressing a crowd of people. This type of public announcement hardware provides someone with extremely limited broadcasting range, often including only a single speaker, but still serves to amplify the user's voice. More advanced versions increase in price considerably, especially with numerous cords, wireless hubs, and adaptors that may be required. This all depends, however, on what a person or business needs in terms of PA system hardware and installation.