Introduction to the application of twisted pair wires for Video Transmission

Because the traditional coaxial cable monitoring system has some shortcomings, especially the Limited transmission distance, it is necessary to seek a solution that is economical, highly transmitted, and with a long transmission distance. In the early days, multi-mode optical fiber and multi-mode optical transceiver were generally used in monitoring systems with a transmission distance of more than five or six hundred meters. This solved the long-distance transmission problem, but the system cost increased a lot, the construction of optical fiber is complex and requires professional personnel and specialized equipment. Therefore, for such a monitoring system that is not too far away, the use of optical fiber and optical terminal is still not economical twisted pair video transmission equipment can be applied to monitoring image transmission, it solves the above problems well.

In fact, twisted pair wires have been used for a long time. telephone transmission uses twisted pair wires, which are used in many industrial control systems, places with high interference, and long-distance transmission, the widely used LAN also uses twisted pair cables. The reason why twisted pair wires are widely used is that they have many advantages such as strong anti-interference ability, long transmission distance, easy wiring, and low price. Because the twisted pair wires also have great signal attenuation, the signal frequency cannot be too high when the transmission distance is long, and the high-speed signal such as Ethernet can only be limited to M. For video signals, the bandwidth reaches 6 MHz. If the video signal is directly transmitted in a twisted pair, the bandwidth will also degrade.

Therefore, video signals must be amplified and compensated for long-distance transmission over twisted pair wires. This function is achieved by twisted pair wires. After a pair of twisted pair video transceiver is added, the image can be transmitted to 1 to 2 km. If the relay method is used, the transmission distance can be increased exponentially, and the quality of the transmitted image can be comparable to that of the optical terminal. The prices of twisted pair wires and twisted pair wires for video transmission equipment are very low. This not only does not increase the system cost, but, when the distance increases, the cost is much lower than that of coaxial cables. Therefore, the monitoring system uses twisted pair wires for transmission has obvious advantages:

◆Long transmission distance and high transmission quality.Because of the advanced processing technology used in the twisted pair transceiver, it can greatly compensate the attenuation of the video signal amplitude of the twisted pair and the attenuation difference between different frequencies, the brightness, color, and real-time performance of the original image are maintained. When the transmission distance reaches 1km or farther, the image signal is basically non-distorted. If the relay method is used, the transmission distance will be further.

◆Easy wiring and high cable Utilization. A pair of telephone lines can be used to transmit video signals. In addition, any one of the five unshielded twisted pair wires widely laid in the building can transmit a video signal, without additional wiring. Even if it is rewiring, the five types of cables are easier than coaxial cables. In addition, there are 4 pairs of twisted pair wires in a category 5 cable. If a pair of wires are used to transmit video signals, the other pairs can also be used to transmit audio, control, power supply, or other signals, improving the cable utilization and avoiding the trouble of separately wiring various signals, reduced the project cost.

◆Strong anti-interference ability.The twisted pair can effectively suppress common-mode interference. Even in a strong interference environment, the twisted pair can transmit excellent image signals. In addition, several pairs of twisted pair wires in a single cable are used to transmit different signals without interference between each other.

◆High reliability and ease of use.When using twisted pair wires to transmit video signals, a dedicated Transmitter must be connected to the front end and a dedicated receiver must be connected to the control center. This twisted pair transmission equipment is cheap and easy to use. It requires no professional knowledge or too many operations. It can be installed once and work stably for a long time.

◆Low Price and convenient materials.Because it is widely used in common category 5 unshielded cables or common telephone lines, it is easy to purchase and the price is very low, which brings great convenience to engineering applications.

1. Comparison between Coaxial Transmission and twisted pair Transmission