Public Address System
A public address system (PA system) is an electronic system comprising microphones, amplifiers, loud speakers, and related equipment. 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.
Microphone voice speaker in school lecture hall, seminar meeting room or educational business conference event for host, teacher or coaching mentor 
City and road video surveillance system as well as public loudspeakers mounted on a steel pole. 
Megaphone on white background. 
School PA system on Red Brick Wall 
Monitor audio stands, professional two-way speaker. Isolated white background 