The transmission system, the monitoring site and the control center always have a certain distance. From the monitoring site to the control center, the image signal is transmitted to the image signal, and the control signal from the control center is transmitted to the site. Therefore, the transmission system includes two parts of the video signal and the control signal transmission.
Video signal transmission, generally using a coaxial cable to transmit video baseband signals, cable can also be used to transmit television signals and transmitted by balanced cable pairs, that is, by telephone cable. Since the cable shields the external electrostatic field and electromagnetic waves, crosstalk can be reduced, and transmission loss is also small. However, when the cable is used as a long-distance transmission medium, the influence of unbalanced low-frequency current on the ground may occur, and sometimes high-frequency interference may occur. The signal transmission bandwidth is 50 Hz to 4 MHz. When the transmission distance is within 200 m, the transmission is transmitted by coaxial cable. The attenuation effect is generally not considered. When the transmission distance is greater than 200 m, the cable attenuation is large, so that the entire bandwidth can be Signals of different frequencies are transmitted and a cable compensation amplifier must be used. In some cases, when wiring is very difficult, wireless transmission such as microwave directional transmission can be used, but it requires frequency resources and needs to be approved by the Radio Management Committee.