Different purchases of security cables in different industries!

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There are many types of security system subsystems, and the demand for security cables is also diverse. Then, from the cable selection of several subsystems of the current security system, how to choose security cables in the security system?


    First, TV monitoring system


    Good video transmission design is a very important part of CCTV surveillance systems. If a well-built system uses cameras, lenses, monitors, and video recorders that produce or process high-quality images, but without a good transmission system, the images that are ultimately seen on the monitor will be unsatisfactory. According to the “barrel rule”, the final image quality will depend on the worst part of the system; this worst part is often the transmission system. The system designer and installer must select the appropriate transmission method, high-quality transmission cable and equipment according to actual needs, and install according to professional standards, in order to achieve the desired transmission effect.


    Video signal transmission generally uses direct modulation technology in the form of baseband frequency (about 8MHz bandwidth). The most common transmission medium is coaxial cable. Coaxial cable is specially designed to transmit video signals. Its frequency loss, image distortion, and image attenuation are relatively small, which can complete the task of transmitting video signals. Generally, the special SYV75 ohm series coaxial cable is used. The commonly used model is SYV75-5 (it has a non-relay transmission distance of 300-500m for video signals); when it is far away, it needs to adopt SYV75-7, SYV75-9 or even SYV75-12 coaxial cable (in actual engineering, the non-relay transmission distance of the thick cable can reach more than 1km); also increase the video amplifier to enhance the brightness, chrominance and synchronization signal of the video, but the interference signal in the line is also Will be amplified, so too many video amplifiers can not be connected in the loop, otherwise there will be saturated image, resulting in image distortion; farther away fiber transmission, fiber transmission has small attenuation, frequency bandwidth, free from electromagnetic interference, A series of advantages, such as light weight and good confidentiality, are mainly used for national, provincial and municipal backbone communication networks, cable TV networks and high-speed broadband computer networks. In CCTV surveillance systems, fiber optic transmission has also become the preferred method for long-distance video and audio and control signal transmission.


    The video signal can also be transmitted over twisted pair, which requires a twisted pair transmission device. Twisted pair transmission equipment is essential in some special applications. For example, when a large number of twisted pairs (referred to as Category 3 or Category 5 in the standard) have been laid in the building according to the integrated wiring standard and a corresponding information interface (RJ45 or RJ11) is left in each relevant room, then new When the closed-circuit television monitoring equipment is added, there is no need to re-wire, and the audio and video signals and control signals can be transmitted through the twisted pair. The transmission of the video signal requires the use of a twisted pair transmission equipment. In addition, twisted pair transmission equipment is also required for applications where a twisted pair (or two-core sheathed wire) has been applied and the image of the front camera needs to be transmitted to the central control room. The function of the twisted pair video transmission equipment is to convert the video signal suitable for unbalanced transmission (that is, suitable for 75Ω coaxial cable transmission) into a video signal suitable for balanced transmission (ie suitable for twisted pair transmission) at the front end; The opposite of the front end, the video signal transmitted over the twisted pair is reconverted to an unbalanced video signal. The twisted pair transmission device itself has video amplification and is therefore suitable for long-distance signal transmission.


    For the different transmission methods above, the transmission components and transmission lines used are quite different.


    Communication cables are generally used in camera units equipped with electric pan/tilt and motorized lenses. Remote control* must be installed on site when in use. The communication transmission cable between the site* and the video matrix switching host of the control center is generally a 2-core shielded communication cable (RVVP) or a Category 3 twisted pair UTP, and the cross-sectional area of each core is 0.3mm2 to 0.5mm2. The basic principle for selecting 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 length of RVV2-1.5 can be used to extend the communication length to more than 2000m. When the communication distance is too long, an RS-485 communication repeater is required.


    The control cable usually refers to a multi-core cable used to control the pan/tilt and the electric variable lens. One end is connected to the controller or the pan/tilt and the motorized lens control terminal, and the other end is directly connected to the pan/tilt and the motorized lens. On the corresponding terminal. Since the control cable provides DC or AC voltage, and the distance is usually short (sometimes less than 1m), there is basically no interference problem, so there is no need to use shielded wires. Most commonly used control cables use 6- or 10-core cables, such as RVV6-0.2 and RVV10-0.12. The 6-core cable is connected to the upper, lower, left, right, automatic and common 6 terminals of the PTZ. The 10-core cable includes the zoom, focus and aperture of the motorized lens in addition to the 6 terminals of the PTZ. , 4 common terminals. In the closed-circuit television monitoring system, the control cable from * to the pan-tilt and the lens is generally not required because of the short distance; and the distance from the controller of the central control room to the pan/tilt and the electric lens is as small as several tens of meters. Then a few hundred meters, the control cable needs to have certain requirements, that is, the wire diameter should be thick, such as RVV10-0.5, RVV10-0.75.


    The sound monitoring cable generally uses a 4-core shielded communication cable (RVVP) or a Category 3 twisted pair UTP with a cross-sectional area of 0.5 mm2 per core. In the absence of interference, it can also be selected as unshielded twisted pair, such as Category 5 twisted pair (4 pairs and 8 cores) commonly used in integrated wiring; because the audio signal of the monitor head in the monitoring system is transmitted to the central control room. The point-to-point wiring method adopted is transmitted with high voltage and small current, so an unshielded 2-core cable can be used, such as RVV2-0.5.


    Second, the burglar alarm system


    Alarm systems based on professional bus formats are currently the most widely used, and cable applications are the most complex, so focus on this discussion.


    RVV2*0.3 (signal line) and RVV4*0.3 (2-core signal 2-core power supply) cable are generally used between the front-end detector and the alarm controller, and the 2-core is generally used between the alarm controller and the terminal security center. Signal line, as for the shielded wire or twisted wire or ordinary sheathed wire, it needs to be determined according to the requirements of various brand products. The rough rule of the wire diameter is determined according to the distance and quality of the alarm controller and the center, but first To determine the location of the security center and the distance of each alarm controller, the farthest distance cannot exceed the length specified by various brands, otherwise it will not meet the requirements of the bus; if the entire alarm area is large, the bus will definitely not meet the requirements. The alarm can be divided into several areas, and the installation position of the sub-control center is determined in each area to ensure that the bus in the area meets the requirements, and the location of the general management center and the location of the sub-management center are determined, and the sub-control center is determined to the general management center. The communication method is RS232--RS485 conversion transmission or RS232-TCP/IP transmission using the integrated wiring system of the cell or management of the sub-management center The software is forwarded to the general management center using a TCP/IP network.


    The power supply of the alarm controller is generally powered by local power instead of the control room. The line is short, generally adopts RVV2×0.5” or above, and can be configured according to the actual line loss. Perimeter alarm and other public area alarm equipment are generally powered. The centralized power supply mode is adopted, and the line is long. Generally, the RVV2*1.0” or higher specification is adopted, and the configuration is based on the actual line loss. The grounding of all power supplies must be uniform.


    Alarms of different nature (such as perimeter alarm, public area alarm bus and household alarm bus) should not use the same bus. The installation position of the junction box should be easy to operate. The high-quality branch interface is used to handle the connection between the bus and the bus for convenient maintenance. And debugging; it is recommended that the bus and other lines be lined up, and the bus should be kept away from the weak current standard and other lines to avoid causing unshielded non-twisted audio lines such as video intercom systems and other high and low frequency interference.


    Third, the building intercom system


    At present, most of the cables used in the building intercom system on the market are RVV, RVVP, SYV and other cables. Their functions are: transmission of voice, data, video images, and cable requirements are also reflected in voice transmission. Quality, the rate of data transmission, the quality and speed of video image transmission, the quality of the cables used in building intercom systems is still relatively high. The cable for transmitting voice signals and alarm signals is mainly RVV4-8*1.0, and the cable for SYV75-5 is mainly used for video transmission. Of course, some new technologies for transmitting signals including video with network cable have appeared. There is no need for video cable; some systems must use RVVP cable in the system for fear of external interference or grounding.


    With the continuous improvement of the intelligentization of the community, the requirements for cables are getting higher and higher, and the cables included therein have five types of lines, RVV signal lines, video lines, and the like.


    The video intercom system uses lines more complicated. Here we will introduce video intercom as an example.


    Direct button type building video intercom system line standard: each indoor unit video, two-way sound and remote unlocking and other wiring terminals are connected to the door machine by bus, but each call line is directly connected to the door machine. Therefore, this type of multi-residential video intercom system uses more cables: video coaxial cable SYV75-5, SYV75-3 series, microphone / speaker / unlock line with a 4-core unshielded or shielded sheathed cable (AVVR4, RVV4 or RVVP4, etc.), the power cable uses a 2-core sheathed cable (AVVR2, RVV2, etc.), and the call line uses a 2-core shielded cable (RVVP2).


    The digital coded button-type video intercom system is generally used in multi-dwelling applications in high-rise residential buildings. According to different manufacturers' equipment system wiring standards, but generally the system basic wiring is: the main line includes video coaxial cable (SYV75-5, SYV75-3, etc.), power cable (AVVR2, RVV2, etc.), audio / Data control line (RVVP4, etc.); household signal line (RVVP6, etc.).


    Most of the residential buildings that install the building video intercom system have a management center machine, and a community wall machine is installed at the entrance of the community wall to enable the residents, management centers and visitors to realize the so-called three-way conversation. The wiring of such a networked system increases the networking line between the unit door machine, the cell door machine and the management center machine, and generally includes video coaxial cable (SYV75-7, SYV75-5, SYV75-3, etc.) transmission. Video signal, 4-core shielded cable (RVVP4-0.5, etc.) transmits audio and control signals.


    In addition, the selection of other security subsystem cable product specifications such as background sound system, garage management system, equipment monitoring system, etc. is relatively simple and will not be described in detail here.