Abstract: A real-time ring-loop surveillance network system is provided. By using digital communication network, multiple channels of media data and control data are transmitted in a ring-loop. The media data includes any forms of digital audio and video data, which is transmitted through 802.3/802.3u physical layer interface. The media data reaches all the stations in the network at the same time, and the number of the stations in the system depends on the system requirements. The number of the channels depends on the transceiver's speed. The present invention defines frames to encompass the media data and control data for transmission. The point-to-point delay is less than 0.15 ms. When 32 stations are connected in a ring-loop, the maximum delay is less than 5 ms. A backup mechanism is also included to detect and automatically switch to maintain the normal operation of the surveillance network system. The monitor signals are also encompassed in frames transmitted in the same network.