Today, the most commonly used paging technology is the use of Self-Amplified Speakers and Horns. This represents nearly 100% of all new installations because it is inexpensive, easy to deploy and easy to troubleshoot. It uses a simple 2-pair connection from the PBX to each speaker. One pair is for the speech and the other pair is for the power.
Each speaker or horn has a small built-in amplifier – just for that speaker. If the amplifier should fail for some reason, the others keep working. Best of all, you can daisy-chain the cabling – in other words, drop and insert as needed.