A public address system is an electronic system comprising microphones, amplifiers, loudspeakers, and related equipment. It increases the apparent volume (loudness) of a human voice, musical instrument, or other acoustic sound source or recorded sound or music. PA systems are used in any public venue that requires that an announcer, performer, etc. be sufficiently audible at a distance or over a large area. Typical applications include sports stadiums, public transportation vehicles and facilities, and live or recorded music venues and events. A PA system may include multiple microphones or other sound sources, a mixing console to combine and modify multiple sources, and multiple amplifiers and loudspeakers for louder volume or wider distribution.
Rear panel of a medium-sized PA system, positioned at one side of the stage at a concert of the musical group Dead Can Dance in 2022, the size being about 3 m from left to right. The setup includes the mixing console for the sound engineer (operating interface with slide controls etc. on the rear) and also the power amplifiers with loudspeaker cables, not in the picture are only the loudspeaker systems distributed around the stage.
A late 19th-century speaking trumpet used by firefighters
A small sports megaphone for cheering at sporting events, next to a 3 in (8 cm) cigarette lighter for scale
Factory, February 1918, page 361
Emergency communication system
An emergency communication system (ECS) is any system that is organized for the primary purpose of supporting one-way and two-way communication of emergency information between both individuals and groups of individuals. These systems are commonly designed to convey information over multiple types of devices, from signal lights to text messaging to live, streaming video, forming a unified communication system intended to optimize communications during emergencies. Contrary to emergency notification systems, which generally deliver emergency information in one direction, emergency communication systems are typically capable of both initiating and receiving information between multiple parties. These systems are often made up of both input devices, sensors, and output/communication devices. Therefore, the origination of information can occur from a variety of sources and locations, from which the system will disseminate that information to one or more target audiences.
A fire control system's RS-232 data connection which an emergency communication system may interface with
Early civil defense type of siren
Short-wave Radio
Audio public address speakers