Public Address Systems Address the Public
Public address systems, sometimes known informally as PA systems, are primarily designed to deliver a message to a large audience. Audiences receiving public address messages may include student classrooms, department store customers, stadium goers and dorm tenants, though public address systems may be used in virtually any environment where a message must be broadcast to a large number of people in a single venue.
Public Address Systems Connect a Microphone to a Loudspeaker
When a user wants to address a group using a public address system, he speaks into an electronic microphone. The microphone converts the speaker's voice into electronic signals, which are transmitted down a pair of connected wires. The wires pass through a powered amplifier to ensure the signal has sufficient strength to reach the destination, then carry the electrical impulses to a series of amplified loudspeakers. The connected speakers convert the electrical signals back to sound vibrations, broadcasting them at volumes approaching 130 decibels (by comparison, a jet engine produces sound at approximately 140 decibels on takeoff). The high volume of the speakers helps ensure as many people as possible hear the broadcast message.
Some PA Systems Allow Two-Way Communication
In certain venues where two-way communication is necessary, public address speakers may be equipped with their own microphone and function as an inter-group communication system, or intercom. In these systems, the person delivering the message can activate the microphone (which, essentially, performs the same service as the PA system in reverse) to hear the group he is addressing. This configuration is especially useful in venues where the addressed group may need to respond to incoming messages or be monitored, such as school classrooms and hospitals.
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