说明：  如果用户的终端设备提供RS-232/485/422通信接口，需要通 过以太网连接到控制中心的应用计算机上，可以在串口终端设备 端选配NP801串口服务器
( If the user s terminal equipment to provide RS-232/485/422 communication interface, need to pass The Ethernet connection to the application of the computer control center, in the serial terminal equipment End of selection of NP801 serial device server)