Wide-band common cable TV monitoring and transmission technology applicable scope

Wide-band common cable TV monitoring and transmission technology applicable scope

Broadband common cable TV surveillance transmission technology (hereinafter referred to as common cable surveillance) is a technological innovation based on traditional surveillance transmission technology. It is a set of multi-functional integrated surveillance image and signal transmission systems produced under the conditions of new technologies. It is the current technology. The best monitoring and transmission solution under the conditions of multi-point, long distance and strong interference. There are many new functions that cannot be achieved by traditional monitoring and transmission technologies (for details, see "A Question and Answer on Broadband Common Cable TV Monitoring and Transmission Technology" by Mr. Ren Hongzhuo), but traditional monitoring technologies still have advantages in general small-scale monitoring systems, and will be synchronized with common cable monitoring There is a long period of time, the following discusses the scope of application of common cable monitoring from five aspects.

1. Number of monitoring points

The number of monitoring points plays a decisive role in adopting traditional monitoring transmission technology or common cable monitoring. The traditional monitoring transmission technology connects up to 4 cables, a video cable (transmits video signals), and a control cable (transmission control) behind each camera. PTZ signal and zoom signal), an audio cable (transmitting monitoring signal), a power cable. In addition to the power supply, the other three cables must enter the main control room. Taking the project of transmitting 800 meters at 60 monitoring points as an example, the traditional monitoring technology needs to lay up to 180 cables with a total cable length of 144 kilometers. ; Large amount of cable laying, huge volume, heavy weight, difficult construction; high laying cost; unsightly; difficult to repair and overhaul.

If the common cable monitoring technology is adopted, corresponding modulation equipment, demodulation equipment, signal amplification equipment and control equipment need to be added, and the equipment cost needs to be increased. Since the common cable monitoring allows 40 video signals, control signals and audio signals to be transmitted simultaneously in a coaxial cable, only two cables need to be laid, the total length of the cable is 2 kilometers, the cost of purchasing the cable is very low, and the purchase is greatly reduced Cable cost; easy cable laying, low construction difficulty; low laying cost; beautiful system; easy maintenance and repair. If there are not many monitoring points, the price advantage of traditional monitoring technology is obvious, and the construction is not difficult. The common cable monitoring solution needs to be equipped with related equipment, and the cost is relatively high. In this case, traditional monitoring technology is applicable.

Taking the project of transmitting 300 meters distance from 3 monitoring points as an example, the traditional monitoring technology needs to lay 9 cables at most, and the total length of the cable is at most 2.7 kilometers. Maintenance and repair are more convenient. If a common cable monitoring technology is used, a 300-meter cable will be laid, but the corresponding equipment needs to be added, and the increased equipment cost is greater than the saved cable cost. It can be seen from the above case that the traditional monitoring technology is suitable for transmission methods with few monitoring points, and the common cable monitoring is suitable for transmission methods with many monitoring points. According to our accumulated engineering construction experience, it is recommended to use a common cable monitoring construction plan for projects with more than 30 monitoring points; for projects with 6 to 30 monitoring points, specific problems should be analyzed, and for 1 to 6 monitoring points Project, it is recommended to use traditional monitoring technology.

2. Transmission distance

The traditional monitoring method uses SYV75-3 coaxial cable to transmit the video signal. Under the index of ensuring the video, the transmission distance is 300 meters, the limit distance can be 500 meters, and 800 meters can be transmitted after the amplifier is installed. At the same time, the system noise is amplified, and the high frequency component is greatly attenuated, which causes the image spectrum to be distorted, and the image quality cannot be guaranteed. The suitable transmission distance of the common cable monitoring is 500M-3000M, which can meet the needs of most users. For ultra-long distance monitoring, the optical cable + common cable can be used to jointly construct the HFC photoelectric hybrid transmission system to solve the monitoring within 200 kilometers Signal bidirectional transmission problem. Therefore, for the transmission distance of more than 500 meters and less than 200 kilometers, common cable monitoring technology is applicable. Transmission within 500 meters can use traditional monitoring technology, and can also use common cable monitoring.

3. Anti-interference

With the continuous development of modern civilization, all kinds of high-power electrical equipment are increasing, and electromagnetic interference is increasing, which makes the electromagnetic environment in most areas not good. These interference frequencies are generally below 4MHz, because traditional monitoring uses video baseband to use coaxial The 0 ～ 6MHz of the cable is used to transmit the image signal. The bandwidth used is completely within the interference band, so the anti-interference ability is poor. The interfered image is prone to twill, mesh, snowflake and ghost, which seriously affects the image quality. By moving the image to a high-frequency carrier transmission above 112 MHz, the common cable monitoring completely avoids common interference frequencies, so the anti-interference ability is strong. Therefore, the common cable monitoring system is applicable in a harsh electromagnetic environment.

4. System expansion

The traditional monitoring technology requires rewiring when expanding the capacity. The construction workload is large, the construction is difficult, and the construction period is long. It is easy to affect the surrounding environment during construction. Party A could not start construction on time or even cancel the expansion plan. If common cable monitoring technology is used, it will produce different results. Still taking the project of 60 monitoring points transmitting a distance of 1000 meters as an example, because the common cable monitoring technology allows 40 channels of required signals to be transmitted simultaneously in one coaxial cable, the system is laid with 2 coaxial cables and the design capacity is to transmit 80 channels For the required signals, 20 signals can be added on the basis of the transmission of the existing 60 signals, that is, 20 monitoring points can be added. In addition to the addition of front-end equipment and demodulation equipment in the computer room as appropriate, no other equipment is required. There is no need to re-wire during expansion. The capacity expansion construction of the common cable monitoring system is small, the construction difficulty is small, the construction period is short, and there is basically no impact on the surrounding environment during construction.

Five, wiring difficulty

In high-rise buildings, the cables will enter the shaft and be fixed to the bridge. Other cables for various purposes are often laid in the shaft. The electromagnetic environment is more complicated and it is easy to interfere with the baseband signals transmitted by traditional monitoring technologies. The bridge frame is firmly fixed for a long time and the construction is difficult; if a large bundle of heavy monitoring signal transmission cables is laid in the office buildings, scientific research institutes, warehouses, communities and other places that have been renovated, the completed decoration will be destroyed, the construction is difficult and unsightly ; In the occasions that need to be overhead or fixed to the wall, the large bundle of heavy monitoring signal transmission cables is difficult to erect, fix, turn at right angles, and buckle the PVC slot plate. These situations are not suitable for the traditional monitoring technology, and the common cable monitoring scheme should be adopted. In addition, in the case of lack of power or the difficulty of laying power lines, the common cable monitoring can use internal feeding to provide power to the front-end camera and modulator.

In short, the common cable monitoring is suitable for large systems and long-distance transmission of various monitoring signals. The system has strong anti-interference ability, simple wiring and easy expansion; traditional monitoring technology is suitable for fewer monitoring points, short transmission distance, fewer peripheral interference sources, and interference An occasion where the signal is not strong and does not require capacity expansion (or a small amount of capacity expansion).

Beijing Hengxing Ketong Sales Director