Based on local area network (LAN) hardware technology and network protocol, is a set of fire alarm & public address system. Transmit digital audio via LAN, not only ensure that the audio signal can achieve long-distance transmission, but also solve signal attenuation, environmental electric/magnetic harassment and other issues in long-distance transmission; Adopt network architecture transmission, significantly reducing the cost of system construction and prewiring, which can bring convenience to system expansion and system maintenance at later stages.