Public Address System consists of speakers (Wall) connected over 1.5Core, twin core, PVC insulated wire (RED & Black) cable connected to PA console. It is divided in to zones based on the overall wattage consumption on that particular floor & area.
All these zones (5 Zones) wires are connected to PA Console. Call stations and keypads are used to individually select particular zone for announcements. Selection and spacing of speakers is made so that all areas of facility are covered and the required sound levels are achieved.
An electronic amplifier, amplifier, or (informally) amp is an electronic device that increases the power  of a signal . The amplifier is often described as the heart or the nervous system of a microphone or loudspeaker.