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    Home > Chemicals Industry > Chemical Technology > Discussion on the selection of wires and cables in the monitoring system

    Discussion on the selection of wires and cables in the monitoring system

    • Last Update: 2022-11-17
    • Source: Internet
    • Author: User
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    Advanced computer networks, especially remote computer networks, are generally divided into two parts
    : communication subnets for data communication and user resource subnets for computer system interconnection.
    It includes transmission lines, hubs, network management centers and other equipment
    .
    The integrated wiring system is the basis of the information network and determines the performance of a security monitoring system
    .
    The designers and installers of the system must choose the appropriate transmission method, high-quality transmission cables and equipment, and install according to professional standards according to actual needs in order to achieve the ideal transmission effect
    .

    Video signal transmission generally adopts direct modulation technology, in the form of baseband frequency (about 8MHz bandwidth), and 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, and the commonly used model is SYV75-5 (its non-relay transmission distance for video signals is generally 300-500m); When the distance is long, it is necessary to use SYV75-7, SYV75-9 or even SYV75-12 coaxial cable (in actual engineering, the transmission distance of thick cable without relay can reach more than 1km); There are also video amplifiers to enhance the brightness, chrominance and synchronization signal of the video, but the interference signal in the line will also be amplified, so too many video amplifiers can not be connected in series in the loop, otherwise saturation will occur, resulting in image distortion; Optical fiber transmission has a series of advantages such as small attenuation, frequency bandwidth, no electromagnetic interference, light weight, good confidentiality, etc.
    , mainly used in national, provincial and municipal backbone communication networks, cable TV networks and high-speed broadband computer networks
    .
    In CCTV monitoring systems, optical fiber transmission has also become the preferred way
    of long-distance video and audio and control signal transmission.

    Video signals can also be transmitted over twisted pair, which requires twisted pair transmission equipment
    .

    Compared with the coaxial cable twisted pair transmission distance is much farther, the maximum can reach 2400 meters, its price is cheap and easy to access, anti-interference ability is also good, the use of PoE power supply can also reduce the amount of
    integrated wiring tasks.
    However, the twisted pair material has weak anti-aging ability, and can only transmit one image
    at a time.
    Therefore, it is more suitable for video surveillance of network cameras in short and medium distances, relatively scattered camera points, or relatively close but concentrated environments, such as banks, chain hotels, supermarkets or university
    campuses.

    In some special applications, twisted pair transmission equipment is indispensable
    .
    For example, when a large number of twisted pairs (called Category 3 or Category 5 wires in the standard) have been laid in the building according to the comprehensive wiring standard, and there is a corresponding information interface (RJ45 or RJ11) in each relevant room, there is no need to rewire when adding CCTV monitoring equipment, and video and audio signals and control signals can be transmitted through twisted pairs, of which twisted pair transmission equipment is used for the transmission of video signals
    .
    In addition, twisted pair transmission equipment is also required for applications that have been laid with twisted pair (or two-core sheathed wire) and need to transmit the image of the front-end camera to the central control room equipment
    .

    The function of twisted pair video transmission equipment is to convert the video signal suitable for unbalanced transmission (that is, suitable for 75 ohm coaxial cable transmission) into a video signal suitable for balanced transmission (that is, suitable for twisted pair transmission) at the front end; At the receiving end, the opposite processing is performed on the front end, and the video signal transmitted through the twisted pair is reconverted into an unbalanced video signal
    .
    The twisted pair transmission device itself has a video amplification effect, so it is also suitable for long-distance signal transmission
    .
    For the above different transmission methods, the transmission components and transmission lines used are quite different
    .

    Communication cables are generally used in camera devices equipped with motorized 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 choosing a communication cable is that the longer the distance, the larger
    the wire diameter.
    For example, the basic communication distance specified by RS-485 communication is 1200m, but the sheath line of RVV2-1.
    5 can be used in actual engineering to extend the communication length to more than
    2000m.
    When the communication distance is too long, RS-485 communication repeaters
    are used.

    The control cable usually refers to the multi-core cable used to control the gimbal and the motorized variable lens, which is connected to the gimbal and motorized lens control terminal of the controller or decoder at one end, and the other end is directly connected to the corresponding terminal of the gimbal and motorized lens
    .
    Since the control cable provides DC or AC voltage, and the distance is generally short (sometimes less than 1m), there is basically no interference problem, so there is no need to use shielded wires
    .
    Most of the commonly used control cables use 6-core or 10-core cables, such as RVV6-0.
    2, RVV10-0.
    12, etc
    .
    Among them, the 6-core cable is connected to the 6 terminals of the gimbal, the top, bottom, left, right, automatic and public, and the 10-core cable includes the zoom, focus, aperture and common 4 terminals of the motorized lens in addition to the 6 terminals
    of the gimbal.
    In the CCTV 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 electric lens is as little as tens of meters, and as much as 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, etc
    .

    Optical fiber is the best medium for long-distance transmission

    The advantages of optical fiber transmission are: long transmission distance, high rate, large bandwidth, small attenuation, the best anti-interference performance, suitable for long-distance and large-scale video transmission, such as road intersection monitoring
    .
    The farthest can even reach tens of hundreds of kilometers, it is transmitted in optical fibers by converting video and control signals into optical signals
    .
    Its equipment using optical fiber transmission is mainly video optical transceiver and optical fiber transceiver, video optical transceiver is mainly used in analog camera signal transmission, it has small signal loss, small noise and distortion, high transmission quality, suitable for long-distance transmission
    .
    The optical fiber transceiver is suitable for the signal transmission of network cameras, and it also has the advantages
    of long transmission distance, small loss and strong anti-interference ability of video optical transceiver.
    With fiber switches, PoE technology can also be used to power front-end cameras, reducing the amount of
    cabling tasks.
    Therefore, optical fiber is the best way
    to solve long-distance transmission.

    Sound monitoring cables generally use 4-core shielded communication cable (RVVP) or Category 3 twisted pair UTP, with a cross-sectional area of 0.
    5mm2
    per core.
    In the absence of interference environment, it can also be selected as unshielded twisted pair, such as Category 5 twisted pair (4 to 8 cores) commonly used in integrated wiring; Since the audio signal of the monitoring head in the monitoring system is transmitted to the central control room by point-to-point wiring method, with high voltage and small current transmission, it is enough to use unshielded 2-core cable, such as RVV2-0.
    5
    .

    In terms of cabling, wired network transmission is the same
    as analog camera cabling.
    In terms of selecting data cables, network surveillance cameras choose ordinary network cable transmission
    .
    In the world of the Internet, there are actually many types of "network cables", and surveillance cameras use twisted pair and coaxial cables
    .

    The development of communication technology is very rapid, and a strong communication system should be taken as the core
    of informatization and intelligence.
    High-speed unshielded twisted pair and optical fiber technology introduces wide-area and local communication networks, including local user circuits and office buildings, so that personal communication and office communication can achieve high speed and large capacity
    .
    Meet the current needs and consider the long-term needs in the future, put forward appropriate goals, and finally use intelligent wiring to improve the flexibility, comprehensiveness and openness of the system to meet every change
    in the new era.


    Advanced computer networks, especially remote computer networks, are generally divided into two parts
    : communication subnets for data communication and user resource subnets for computer system interconnection.
    It includes transmission lines, hubs, network management centers and other equipment
    .
    The integrated wiring system is the basis of the information network and determines the performance of a security monitoring system
    .
    The designers and installers of the system must choose the appropriate transmission method, high-quality transmission cables and equipment, and install according to professional standards according to actual needs in order to achieve the ideal transmission effect
    .

    Video signal transmission generally adopts direct modulation technology, in the form of baseband frequency (about 8MHz bandwidth), and 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, and the commonly used model is SYV75-5 (its non-relay transmission distance for video signals is generally 300-500m); When the distance is long, it is necessary to use SYV75-7, SYV75-9 or even SYV75-12 coaxial cable (in actual engineering, the transmission distance of thick cable without relay can reach more than 1km); There are also video amplifiers to enhance the brightness, chrominance and synchronization signal of the video, but the interference signal in the line will also be amplified, so too many video amplifiers can not be connected in series in the loop, otherwise saturation will occur, resulting in image distortion; Optical fiber transmission has a series of advantages such as small attenuation, frequency bandwidth, no electromagnetic interference, light weight, good confidentiality, etc.
    , mainly used in national, provincial and municipal backbone communication networks, cable TV networks and high-speed broadband computer networks
    .
    In CCTV monitoring systems, optical fiber transmission has also become the preferred way
    of long-distance video and audio and control signal transmission.

    Video signals can also be transmitted over twisted pair, which requires twisted pair transmission equipment
    .

    Compared with the coaxial cable twisted pair transmission distance is much farther, the maximum can reach 2400 meters, its price is cheap and easy to access, anti-interference ability is also good, the use of PoE power supply can also reduce the amount of
    integrated wiring tasks.
    However, the twisted pair material has weak anti-aging ability, and can only transmit one image
    at a time.
    Therefore, it is more suitable for video surveillance of network cameras in short and medium distances, relatively scattered camera points, or relatively close but concentrated environments, such as banks, chain hotels, supermarkets or university
    campuses.

    In some special applications, twisted pair transmission equipment is indispensable
    .
    For example, when a large number of twisted pairs (called Category 3 or Category 5 wires in the standard) have been laid in the building according to the comprehensive wiring standard, and there is a corresponding information interface (RJ45 or RJ11) in each relevant room, there is no need to rewire when adding CCTV monitoring equipment, and video and audio signals and control signals can be transmitted through twisted pairs, of which twisted pair transmission equipment is used for the transmission of video signals
    .
    In addition, twisted pair transmission equipment is also required for applications that have been laid with twisted pair (or two-core sheathed wire) and need to transmit the image of the front-end camera to the central control room equipment
    .

    The function of twisted pair video transmission equipment is to convert the video signal suitable for unbalanced transmission (that is, suitable for 75 ohm coaxial cable transmission) into a video signal suitable for balanced transmission (that is, suitable for twisted pair transmission) at the front end; At the receiving end, the opposite processing is performed on the front end, and the video signal transmitted through the twisted pair is reconverted into an unbalanced video signal
    .
    The twisted pair transmission device itself has a video amplification effect, so it is also suitable for long-distance signal transmission
    .
    For the above different transmission methods, the transmission components and transmission lines used are quite different
    .

    Communication cables are generally used in camera devices equipped with motorized 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 choosing a communication cable is that the longer the distance, the larger
    the wire diameter.
    For example, the basic communication distance specified by RS-485 communication is 1200m, but the sheath line of RVV2-1.
    5 can be used in actual engineering to extend the communication length to more than
    2000m.
    When the communication distance is too long, RS-485 communication repeaters
    are used.

    The control cable usually refers to the multi-core cable used to control the gimbal and the motorized variable lens, which is connected to the gimbal and motorized lens control terminal of the controller or decoder at one end, and the other end is directly connected to the corresponding terminal of the gimbal and motorized lens
    .
    Since the control cable provides DC or AC voltage, and the distance is generally short (sometimes less than 1m), there is basically no interference problem, so there is no need to use shielded wires
    .
    Most of the commonly used control cables use 6-core or 10-core cables, such as RVV6-0.
    2, RVV10-0.
    12, etc
    .
    Among them, the 6-core cable is connected to the 6 terminals of the gimbal, the top, bottom, left, right, automatic and public, and the 10-core cable includes the zoom, focus, aperture and common 4 terminals of the motorized lens in addition to the 6 terminals
    of the gimbal.
    In the CCTV 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 electric lens is as little as tens of meters, and as much as 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, etc
    .

    Optical fiber is the best medium for long-distance transmission

    The advantages of optical fiber transmission are: long transmission distance, high rate, large bandwidth, small attenuation, the best anti-interference performance, suitable for long-distance and large-scale video transmission, such as road intersection monitoring
    .
    The farthest can even reach tens of hundreds of kilometers, it is transmitted in optical fibers by converting video and control signals into optical signals
    .
    Its equipment using optical fiber transmission is mainly video optical transceiver and optical fiber transceiver, video optical transceiver is mainly used in analog camera signal transmission, it has small signal loss, small noise and distortion, high transmission quality, suitable for long-distance transmission
    .
    The optical fiber transceiver is suitable for the signal transmission of network cameras, and it also has the advantages
    of long transmission distance, small loss and strong anti-interference ability of video optical transceiver.
    With fiber switches, PoE technology can also be used to power front-end cameras, reducing the amount of
    cabling tasks.
    Therefore, optical fiber is the best way
    to solve long-distance transmission.

    Sound monitoring cables generally use 4-core shielded communication cable (RVVP) or Category 3 twisted pair UTP, with a cross-sectional area of 0.
    5mm2
    per core.
    In the absence of interference environment, it can also be selected as unshielded twisted pair, such as Category 5 twisted pair (4 to 8 cores) commonly used in integrated wiring; Since the audio signal of the monitoring head in the monitoring system is transmitted to the central control room by point-to-point wiring method, with high voltage and small current transmission, it is enough to use unshielded 2-core cable, such as RVV2-0.
    5
    .

    In terms of cabling, wired network transmission is the same
    as analog camera cabling.
    In terms of selecting data cables, network surveillance cameras choose ordinary network cable transmission
    .
    In the world of the Internet, there are actually many types of "network cables", and surveillance cameras use twisted pair and coaxial cables
    .

    The development of communication technology is very rapid, and a strong communication system should be taken as the core
    of informatization and intelligence.
    High-speed unshielded twisted pair and optical fiber technology introduces wide-area and local communication networks, including local user circuits and office buildings, so that personal communication and office communication can achieve high speed and large capacity
    .
    Meet the current needs and consider the long-term needs in the future, put forward appropriate goals, and finally use intelligent wiring to improve the flexibility, comprehensiveness and openness of the system to meet every change
    in the new era.

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