1, baseband video transmission: the most traditional TV monitor transmission mode, 0 ~ 6MHz video baseband signal without any treatment, direct transmission of analog signals through coaxial cable (unbalanced). Its advantages are: the short-range transmission loss of image signal is small, low cost, stable system. Disadvantages: short transmission distance, high frequency attenuation greater than 300 meters above, can not guarantee the quality of the image; need cloth one way video signal cable, transmission control the signal separately cloth cable; structure for the star-shaped structure, wiring capacity, maintenance difficulties, poor scalability, suitable for small systems.
2, the optical fiber transmission: the common simulation Optical and Digital Optical solve dozens or even hundreds of kilometers of transmission of TV monitoring solution, convert video and control signals for the laser signal in optical fibers. Its advantages are: the transmission distance attenuation, anti-jamming performance is best suitable for long-distance transmission. The disadvantage is: for the monitoring signal transmission within a few kilometers is not enough economic; optical splicing and maintenance needs of professional and technical personnel and equipment operation processing, maintenance, technical requirements, and not easy to upgrade expansion.
3.Network transmission: solve Metro between distant point is extremely decentralized control transmission using MPEG2 / 4, H.264 video and audio compression format transmission control signal. Its advantages are: a network video server, Internet network installed on the remote monitoring software can monitor and control as monitoring signal Upload equipment. The disadvantages are: the network bandwidth and speed limit can only transfer the small-screen, low-quality images; several dozen frames per second can only transfer images, the animation is very clear and there is a delay, and not be able to do real-time monitoring .
4. Microwave transmission: It is one of a few kilometers or even tens of kilometers is not easy wiring solution for workplace monitoring transmission. FM modulation or AM modulation approach, the image carrying the high-frequency carrier converted to high-frequency electromagnetic waves transmitted in the air. Its advantages are: eliminating the need for wiring and cable maintenance costs can be dynamic real-time transmission of broadcast-quality images. The disadvantages are: microwave transmission bands above 1GHz, commonly used in the L-band (1.0 to 2.0GHz), S-band (2.0 to 3.0GHz), Ku-band (10 ~ 12GHz), the transmission environment is an open space vulnerable to external electromagnetic interference; microwave signal for transmission line, do not have a the mountain building block; Ku-band more seriously affected by the weather, rain and snow will be especially severe rain fade imagine.
5 twisted pair transmission (balance transfer): a baseband video transmission, 75Ω unbalanced mode converted to balanced mode transmission. One solution solve surveillance images 1Km transfer complex electromagnetic environment occasions, the monitor image signal processing by a the balanced symmetric way transmission. Its advantages are: wiring simple, low-cost, anti-common-mode dry worries performance. The disadvantage: only solve within 1Km monitoring image transmission, and a twisted-pair can only transmit one image, not suitable for application in the large and medium-sized monitor; twisted pair fragile and aging ability, not suitable for field transmission; dual Stranded transmit high frequency attenuation greater image color will be a great loss.
6, the broadband of cable transmission: the video using AM modulation, audio FM the equipped, FSK data signal modulation technology, integrated into the dozens of road surveillance images, audio, control and alarm signal "a" coaxial cable in the two-way transmission. Its advantages are: to take full advantage of the coaxial cable of the resource space, 40-way audio and video, and control signals in the same cable, two-way transmission, "Link"; simple construction, easy maintenance, substantial savings in the cost of materials and construction costs; frequency division multiplexing dispersed solve teleportation point wiring is difficult to monitor the transmission problem; RF transmission mode attenuation only a small carrier signal, image signal attenuation, brightness, chroma transmission synchronization nested national standards in image quality more than 4.5; 75Ω coaxial unbalanced transmission so that it has a very strong anti-jamming capability, complex electromagnetic environment occasions able to ensure the quality of the image. Its disadvantages are: the use of a weak signal transmission, high technical requirements of system debugging must use professional equipment. Broadband modulation end external AC220V AC power, but most of the monitoring points have this condition.
