The public address system is a broadcast that serves the public within a specific scope. Under normal circumstances, the public broadcasting system signals are transmitted through the broadcasting lines arranged in the broadcasting service area, usually a one-way (downstream) cable broadcasting.
The public address system is usually set up in agencies, troops, enterprises, schools, communities, buildings, supermarkets and various venues, such as school public address system, to release news and internal information, release schedule signals, provide background music, and use for paging (for example, broadcasting to find people) and forcibly inserting emergency broadcasts of catastrophic accidents, etc. The public address system also uses wireless transmission, but it is not mainstream.
A public address system must at least be equipped with broadcasting speakers, broadcasting power amplifiers, and microphones. Low-power broadcast power amplifiers below 650W usually come with pre-functions and do not need to be equipped with pre-amplifiers, commonly known as combined broadcasters. Broadcast power amplifiers with higher power (for example, 650W watts or more) usually need to be equipped with a broadcast preamplifier. However, whether it is a pre-amplifier in a combined broadcaster or a separate broadcast pre-amplifier, its input ports should be prioritized.
The public address system usually has at least one microphone at the highest priority. The signal of this microphone can automatically suppress other input signals (the so-called automatic "silence" function), so that the emergency broadcast can be inserted forcibly during paging and emergencies. The terms in the public address system include microphones, lines, power amplifiers, speakers, etc., which are familiar to ordinary electro-acoustic workers or electro-acoustic enthusiasts. However, the broadcasting lines, broadcasting power amplifiers and broadcasting speakers are slightly different from ordinary speaker cables, power amplifiers and speakers.