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Analysis of the advantages and disadvantages of wired methods for explosion-proof camera monitoring projects

2024-4-11      View:
1. Video baseband transmission: The most traditional TV monitoring transmission method does not perform any processing on 0~6MHz video baseband signals, and directly transmits analog signals through coaxial cables (unbalanced).

Advantages: small loss of image signal in short-distance transmission, low cost, and stable system.

Disadvantages: The transmission distance is short, the high-frequency component is attenuated greatly above 300 meters, and the image quality cannot be guaranteed. The amount of wiring is large, maintenance is difficult, and scalability is poor, so it is suitable for small systems. Especially today when non-standard cables are prevalent, when you find that there is video interference, characters jump after adding a matrix, and there is interference in the picture after passing through the video splitter, check whether the cable you are using meets the standards?

2. Optical fiber transmission: Common ones include analog optical transceivers and digital optical transceivers, which are the best solution for TV surveillance transmission for tens or even hundreds of kilometers. Video and control signals are converted into laser signals for transmission in optical fibers.

Advantages: long transmission distance, small attenuation, best anti-interference performance, suitable for long-distance transmission. Standard optical transceivers have a transmission distance of 0-20 kilometers, and 8-way optical transceivers are the most cost-effective. This is related to the optical head, as all friends who make optical transceivers know. Optical transceivers are very cheap now, but good quality ones are still very expensive.

Disadvantages: It is not economical enough for monitoring signal transmission within a few kilometers; optical splicing and maintenance require professional technicians and equipment operation, high maintenance technical requirements, and it is not easy to upgrade and expand capacity. In order to save cheap optical jumpers and flanges, some engineers directly connect equipment with pigtails. When repairing in the future, you will know how important that jumper and flange are.

3. Network transmission: To solve the problem of long-distance and extremely dispersed monitoring transmission between metropolitan areas, MPEG2/4 and H.264 audio and video compression formats are used to transmit monitoring signals.

Advantages: The network video server is used as the monitoring signal uploading device, and remote monitoring software can be installed on the Internet to monitor and control.

Disadvantages: Limited by network bandwidth and speed, it can only transmit small-screen, low-quality images; it can only transmit a few to a dozen frames of images per second, and the animation effect is very obvious and delayed, making real-time monitoring impossible. But I'm very optimistic about network transmission.

4. Twisted pair transmission (balanced transmission): It is also a type of video baseband transmission, which converts the 75Ω unbalanced mode into a balanced mode for transmission. It is one of the solutions for the transmission of surveillance images within 1Km and the complex electromagnetic environment. It processes the surveillance image signals and transmits them in a balanced and symmetrical manner.

The advantages are: simple wiring, low cost, and strong resistance to common mode interference.

Disadvantages: It can only transmit surveillance images within 1Km, and one twisted pair can only transmit one image, so it is not suitable for use in large and medium-sized surveillance; the twisted pair is fragile and has poor aging resistance, so it is not suitable for field transmission; the twisted pair is not suitable for field transmission. The transmitted high-frequency components are attenuated greatly, and the image color will be greatly lost.

5. Common cable transmission: The video uses amplitude modulation modulation, FSK data modulation and other technologies to integrate dozens of monitoring images, audio, control and alarm signals into "one" coaxial cable for bidirectional transmission. To put it bluntly, the cable TV network works backwards. It is entirely a closed-circuit television transmission technology, which is very mature and practical.

Advantages: full use of the resource space of coaxial cables, twenty audio, video and control signals are transmitted bidirectionally in the same cable to achieve "one line communication"; simple construction and convenient maintenance, saving a lot of material costs and construction costs; frequency division Multiplexing technology solves the monitoring and transmission problems of scattered long-distance transmission points and difficult wiring; the radio frequency transmission method only attenuates the carrier signal, and the image signal attenuation is very small. The brightness and chroma transmission are synchronously nested to ensure that the image quality reaches the national standard of level 4 or above; The use of 75Ω coaxial unbalanced transmission makes it have very strong anti-interference ability, and the image quality can still be guaranteed in complex electromagnetic environments.

Disadvantages: Using cable TV transmission technology is a joint project. For those who are involved in monitoring, it is a bit cross-industry. Common cable transmission is mainly about design. Of course, there are also levels in products. Experience is very important for many aspects of radio frequency. System debugging technology requires high standards and professional instruments must be used.

Whenever the security industry mentions development trends, the words that appear most frequently must be high-definition, digital, and intelligence. These are already three recognized development trends. However, in the process of realizing high-definition, digitalization and intelligence in the monitoring system, video wireless transmission plays a bridge role. The convenience and flexibility of wireless transmission closely connect the three to achieve application in the security industry.