ITC digital IP network PA system is a pure digital hands-free transmission intercom system. It adapts the most advanced IP audio transmission technology to transfer the audio signal in data form through LAN and WAN. It solves such problems that traditional PA systems possess shot-distance transmission, bad interactivity and so on. IP network PA system can be constructed based on existing computer network, independent wiring is of no necessary when installation. It is the real pure digital network PA system, which is highly distinguished from the traditional PA systems. The system is widely used in: banks, express railways, highways, safe cities, nuclear power stations, chain organizations, factories, prisons, mines, forests and parks.