After going through the stages of analog imaging and PC based digital transmission, monitoring systems have advanced to the TCP/IP based technology in a fast pace. As a result of the rapid popularization of the Internet, low cost remote monitoring and control systems can be readily realized. In the TCP/IP technology network based monitoring system, the front-end sound and video acquisition equipment can compress the source signal and then transmit it over the network. Authorized users in a local or remote area can achieve real-time monitoring and control through the local area network (LAN) or Wide Area Network (WAN). This system has the advantage of small sized front-end equipment, easy installation and the signal can be sent over the Ethernet or WAN.
        However, although this kind of system has the said advantages, the ordinary Ethernet cable has a maximum transmitting range of only 100m according to the ISO standard. This limitation has caused big problems for monitoring system integrators when placing the network cameras in the appropriate locations.
        In view of this problem, our company has developed the GTL6010 series of special modems with a transmission speed of up to 10Mbps to be used in monitoring systems. Just place a pair of such modems between the network camera and the switchboard, and it can provide 500m of basic transmission distance using copper core twisted pair wires. With the use of repeaters, it can even achieve a transmitting range of 1-2Km, thus greatly increase the flexibility of placing the network cameras. In addition, a multi-drop type of monitoring system can be built over a twisted pair line with the use of multiple modems. The connection diagram of a long distance monitoring system based on our built-in modems is shown as follows: