Selection of weak current cables

Video signal transmission generally adopts direct modulation technology, in the form of baseband frequency (about 8MHz bandwidth), the most commonly used transmission medium is coaxial cable; Coaxial cable is specially designed to transmit video signals, and its frequency loss, image distortion, and image attenuation amplitude are relatively small, which can well complete the task of transmitting video signals.
Generally, special SYV75 ohm series coaxial cable is used; The commonly used model is SYV75-5 (its non-relay transmission distance for video signals is generally 300-500m); When the distance is long, SYV75-7 and SYV75-9 coaxial cables need to be used (in actual engineering, the transmission distance of thick cables without trunking can reach more than 1km)
Communication cables are generally used in camera devices equipped with electric gimbal and motorized lenses, and remote control decoders need to be installed on site when used; The communication transmission cable between the field decoder and the video matrix switching host of the control center generally adopts 2-core shielded communication cable (RVVP) or 3 types of twisted pair UTP, with a cross-sectional area of 0.3mm² ~ 0.5mm² per core; the basic principle of selecting a communication cable is that the longer the distance, the larger the wire diameter; the basic communication distance stipulated by RS-485 communication is 1200m, but the sheath line of RVV2-1.5 can be extended to more than 2000m in actual engineering.
Communication cables are generally used in camera devices equipped with electric gimbal and motorized lenses, and remote control decoders need to be installed on site when used; The communication transmission cable between the field decoder and the video matrix switching host of the control center generally adopts 2-core shielded communication cable (RVVP) or 3 types of twisted pair UTP, with a cross-sectional area of 0.3mm² ~ 0.5mm² per core; the basic principle of selecting a communication cable is that the longer the distance, the larger the wire diameter; the basic communication distance stipulated by RS-485 communication is 1200m, but the sheath line of RVV2-1.5 can be extended to more than 2000m in actual engineering.
Control cables usually refer to multi-core cables used to control gimbal and motorized variable lenses; One end of the control cable is connected to the gimbal and motorized lens control terminal of the controller or decoder, and the other end is directly connected to the corresponding terminal of the gimbal and motorized lens; The control cable provides DC or AC voltage, and the distance is generally short (sometimes less than 1m), and there is basically no interference problem, so there is no need to use shielded wire

Most of the commonly used control cables use 6-core or 10-core cables, such as RVV6-0.2, RVV10-0.12; of which the 6-core cables are connected to the up, bottom, left, right, automatic, and public 6 terminals of the gimbal, and the 10-core cable includes the zoom, focus, aperture, and common 4 terminals of the electric lens in addition to the 6 terminals connected to the gimbal; In the monitoring system, the control cable from the decoder to the gimbal and the lens is generally not required due to the relatively short distance; The distance from the controller in the central control room to the gimbal and the motorized lens is as little as tens of meters, or hundreds of meters, and the control cable needs to have certain requirements, that is, the wire diameter should be thick, such as RVV10-0.5, RVV10-0.75
Sound monitoring cables generally use 4-core shielded communication cables (RVVP) or Category 3 twisted pair UTPs with a cross-sectional area of 0.5mm² per core
The audio signal of the monitoring head in the monitoring system is transmitted to the central control room by point-to-point wiring, with high voltage and small current transmission, so unshielded 2-core cable can be used, such as RVV2-0.5

RVV2*0.3 (signal line) and RVV4*0.3 (2-core signal + 2-core power supply) cables are generally used between the front-end detector and the alarm controller; A 2-core signal line is generally used between the alarm controller and the terminal security center
Whether the signal line is shielded or twisted pair or ordinary sheathed wire needs to be determined according to the requirements of various brands of products; The thick specification of the signal line diameter is determined according to the distance and quality of the alarm controller and the center; The power supply of the alarm controller generally adopts local power intake instead of centralized power supply in the control room, and the line is short, generally using RVV 2×0.5" or more specifications; The power supply of perimeter alarm and other public area alarm equipment generally adopts centralized power supply mode, the line is long, and the RVV2*1.0" or above specifications are generally adopted
Most of the cables used in building intercom systems are RVV, RVVP, SYV and other cables
It has: transmission of voice, data, video images, and cable requirements are also manifested in the quality of voice transmission, the rate of data transmission, the quality and rate of video image transmission, etc