Analysis on How to Choose cable products in the security system

A sound video transmission design is a very important part of the CCTV system. If a set of built systems choose cameras, lenses, monitors, and video recorders that can produce or process high-quality images, but there is no good transmission system, eventually, the images seen on the monitor will not be satisfactory. According to the "barrel rule", the final image quality will depend on the worst part of the entire system, which is often the transmission system. System designers and installers must select the appropriate transmission mode, high-quality transmission cables and equipment, and install them according to professional standards to achieve the desired transmission effect.

Video signal transmission generally uses direct modulation technology, which is transmitted in the form of a baseband frequency of about 8 MHz bandwidth. The most common transmission medium is a coaxial cable. The coaxial cable is specially designed to transmit video signals. Its frequency loss, image distortion, and image attenuation are all relatively small, which can well complete the task of transmitting video signals. Domestic general use of real-core polyvinyl chloride insulated RF coaxial cable SYV-75 series, commonly used models for SYV-75-5 it to video signal without relay transmission distance is generally 500 meters), distance is relatively far, SYV-75-7, SYV-75-9 or even SYV-75-12 coaxial cable in the actual engineering, the non-relay transmission distance of the crude cable can reach more than 1000 meters ); some video amplifiers are added to enhance the brightness, color, and synchronization signals of the video. However, interference signals in the line are also amplified, so too many video amplifiers cannot be connected in the loop, otherwise, saturated images may occur, resulting in distortion of the image. Optical Fiber Transmission is adopted for farther distances, optical Fiber Transmission has a series of advantages, such as low attenuation, high frequency bandwidth, no electromagnetic interference, light weight, and good confidentiality, it is mainly used for national and provincial-municipal backbone communication networks, cable TV networks, and high-speed broadband computer networks. In the closed-circuit television monitoring system, optical fiber transmission has become the first choice for long-distance transmission of video and audio and control signals.

Coaxial cables used internationally for video systems include RG series and JIS series.

Video signals can also be transmitted using twisted pair cables. This requires a twisted pair transmission device. In some special applications, twisted pair wires are essential. For example, when a large number of category-5 or category-5e cables have been laid in a building according to the Integrated Wiring standard) and corresponding information interfaces RJ45 or limit 11 are left in the relevant rooms ), when a closed-circuit television monitoring device is added, no cabling is required. The audio and video signals and control signals can be transmitted through twisted pair wires. The transmission of video signals must use twisted pair wires. In addition, for applications where the front-end camera images need to be transmitted to the central control room equipment, the twisted pair wire transmission equipment is also required. The function of twisted pair video transmission equipment is to convert video signals suitable for non-balanced transmission (75 Ω coaxial cable transmission) to video signals suitable for balanced transmission (that is, suitable for twisted pair transmission) at the front end; opposite to the front-end processing at the receiving end, the video signal sent from twisted pair wires is converted into a non-balanced video signal. The twisted pair transmission device has the function of video amplification, so it is also suitable for long-distance video transmission.

For the above different transmission modes, the transmission components and transmission lines are quite different. Communication cables are generally used in camera devices with an electric cloud platform and an electric lens. Remote Control decoder must be installed on site during use. Communication and transmission cables between the scene decoder and the Control Center's video matrix switching host. Generally, two-core shielded cable RVVP is used, with a cross-sectional area of 0.3 ~ 5mm2) or 3 class twisted pair UTP ). The basic principle for selecting a communication cable is that the longer the distance, the larger the cross-sectional area. For example, the basic communication distance of RS-485 communication is 1200 m, but in the actual project, the RVV2X1.5 protection line can be used to extend the communication length to more than 2000 meters. When the communication distance is too long, the use of RS-485 communication repeater.

The control signal cable is usually a multi-core cable used to control the cloud platform and the electric variable lens. It is connected to the cloud platform or the electric lens control terminal of the Controller or decoder, the other end is directly connected to the corresponding terminal of the cloud platform and electric lens. Because the control cable provides DC or AC voltage, and the distance is usually very short, sometimes less than 1 meter), there is basically no interference problem, so no need to use the shielding line. Most commonly used control cables use 6-or 10-Core Cables, such as AVVR6X0.2 and AVVR10X0.12. The six-Core Cables are connected to the upper, lower, left, right, automatic, and public terminals of the cloud platform, in addition to six terminals connected to the cloud platform, the 10-core cable also includes four terminals, namely, power lens doubling, focusing, aperture, and public terminal. In the CCTV system, the control cable from the decoder to the cloud platform and the lens is generally not required due to the short distance; the distance from the Controller of the central control room to the cloud platform and the electric lens is several dozen meters, while the distance is several hundred meters. Therefore, the control cable must have certain requirements, that is, the cross-sectional area must be large, for example, RVV10X0.5 and RVV10X0.75 are used.

Generally, a 4-core shielded cable RVVP is used, and the cross-sectional area of each core is 5mm2 MPa.) or three types of twisted pair wires (UTP) are used. In the absence of interference, unshielded twisted pair wires can also be used, for example, 4-to-8-core 5-category twisted pair wires commonly used in integrated wiring ), because the audio signal from the monitoring head in the monitoring system is transmitted to the central control room through point-to-point wiring and transmission with high voltage and small current, a non-shielded 2-core cable is used, such as RVV2X0.5. Medium

In particular, the elevator video surveillance system: elevator room monitoring is getting more and more people's attention, but the elevator room environment is relatively special, because the elevator car is a very frequent place to move, the cables used by the video surveillance system of the corresponding elevator are also very special cables.

Generally, a Video Wire Rope is added with a strong core to adapt to the stress generated during movement. The high-strength bending-resistant conductor material is required for the internal conductor of the Video Wire. Otherwise, the core is often broken, causing poor image, in addition, various types of interference between the elevator are very severe, and the shielding of the Video Wire Core is also required to adopt an encrypted model, most of which are for double-layer braided mesh shielding. Also, twisted pair wires are used for video transmission, however, the twisted pair wires must be attached to the network system, and the cables must be bundled on the cables accompanying the electric sample.