Selection of Cable Products in Security System

First, closed-circuit television monitoring system (CCTV)

Good video transmission design is a very important part of the CCTV system. If a well-established system uses cameras, lenses, monitors, and video recorders that can produce or process high-quality images, but there is no good transmission system, the images eventually seen on the monitor will be unsatisfactory. According to the “law of barrels”, the final image quality will depend on the worst link in the entire system, and the worst link is often the transmission system. The system designers and installers must select the appropriate transmission method, high-quality transmission cables and equipment according to actual needs, and install them according to professional standards in order to achieve the desired transmission effect.

The video signal transmission generally adopts the direct modulation technology, transmits in the form of the base band frequency (about 8MHz bandwidth), the most common transmission medium is the coaxial cable. Coaxial cable is specially designed to transmit video signals. Its frequency loss, image distortion, and image attenuation are relatively small, which can well complete the task of transmitting video signals. The domestic use of solid-core PVC insulated RF coaxial cable SYV-75 series, the commonly used model is SYV-75-5 (its non-relay transmission distance for video signals is generally 500 meters), when the distance is far, use Coaxial cable of SYV-75-7, SYV-75-9 and even SYV-75-12 (In practical projects, the thick cable has an unrelayed transmission distance of more than 1000 meters); there are also video enhancement amplifiers to enhance the video The luminance, chrominance and synchronization signals, but the interference signal in the line will be amplified, so too many video amplifiers cannot be connected in series in the loop, otherwise saturated images will appear, leading to distortion of the image; the optical fiber transmission method will be used farther away. Optical fiber transmission has a series of advantages such as small attenuation, wide frequency band, no electromagnetic interference, light weight and good confidentiality. It is mainly used in national and provincial-level backbone communication networks, cable television networks and high-speed broadband computer networks. In closed-circuit television monitoring systems, optical fiber transmission has also become the preferred method for long-distance video, audio, and control signal transmission.

Internationally used coaxial cable for video systems are RG series, JIS series, etc.

Video signals can also be transmitted using data cables (twisted pair), which requires twisted pair transmission equipment. In some special applications, twisted pair transmission equipment is essential. For example, when a large number of twisted pairs (Class 5 or Category 5e) in the building have been laid out in the building and the corresponding information interfaces (RJ45 or RJ11) are left in the relevant rooms, the new CCTV monitoring equipment does not require wiring, video and audio signals and control signals can be transmitted through the twisted pair, in which the transmission of video signals requires the use of twisted pair transmission equipment. In addition, twisted-pair transmission equipment is also required for applications where twisted-pair cables (or two-core sheathed cables) have been laid and front-end camera images are transmitted to central control room equipment. 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 the video signal suitable for balanced transmission (that is, suitable for twisted pair transmission) at the front end; The reverse processing of the front end converts the video signal transmitted through the twisted pair into an unbalanced video signal. The twisted pair transmission device itself has a video amplification effect and is therefore also suitable for long distance video transmission.

For the above different transmission methods, the transmission components and the transmission lines used are quite different. The communication cable is generally used in an imaging device equipped with an electric pan/tilt head and an electric lens, and a remote control decoder must be installed in the field at the time of use. The communication transmission cable between the on-site decoder and the video matrix switching host of the control center generally uses a 2-core shielded cable (RVVP, a cross-sectional area of ​​0.3 to 0.5 mm2 per core) or a Category 3 twisted pair (UTP). The basic principle for selecting a communication cable is that the longer the distance, the larger the cross-sectional area. For example: The basic communication distance that RS-485 communication stipulates is 1200m, but in actual project choose RVV 2X1.5 sheath wire to expand the communication length to more than 2000 meters. When the communication distance is too long, an RS-485 communication repeater is required.

The control signal cable usually refers to a multi-core cable used to control the pan/tilt and the electric variable lens. One end of the control signal cable is connected to the pan/tilt/electric lens control terminal of the controller or the decoder, and the other end is directly connected to the pan/tilt, On the corresponding terminals of the electric lens. Since the control cable provides DC or AC voltage, and the distance is usually very short (sometimes less than 1 meter), there is basically no interference problem, so no shielded cable is needed. Commonly used control cables mostly use 6- or 10-core cables, such as AVVR 6X0.2 and AVVR 10X0.12. The 6-core cable is connected to the top, bottom, left, right, automatic, and public 6 terminals of the PTZ respectively. The 10-core cable includes the zoom, focus, and aperture of the electric lens in addition to the 6 terminals of the PTZ. , Public 4 terminals. In the CCTV system, the control cable from the decoder to the pan/tilt head and the lens does not require special requirements due to the relatively short distance; however, the distance from the controller of the central control room to the pan/tilt head and the electric lens is as short as several tens of meters. For a few hundred meters, there are certain requirements for the control cable, that is, the cross-sectional area should be large, such as RVV 10X0.5, RVV 10X0.75, etc.

Audio monitoring cable (audio cable) generally uses 4-core shielded cable (RVVP, 0.5mm2 per core cross-section) or Category 3 twisted pair UTP. In the uninterrupted environment, unshielded twisted pairs can also be used, such as the commonly used Category 5 twisted pair cable (4 to 8 cores) in the integrated cabling, since the audio signal from the monitor head in the monitoring system is transmitted to the central control room. The point-to-point wiring method uses high-voltage and low-current transmission, so unshielded 2-core cable can be used, such as RVV 2X0.5.

The elevator video monitoring system is especially explained here: The monitoring of the elevator room is increasingly valued by people, but the environment of the elevator room is relatively special because the elevator car is a very frequent occasion and the corresponding elevator video monitoring The cable used by the system is also a very special dedicated cable.

The video cable generally has a steel wire rope reinforcing core to adapt to the stress generated during the movement. The inner conductor of the video cable requires a high-strength and bending-resistant conductor material, otherwise the core will often break the image and the elevator will have various interferences. Requires shielding of the video cable cores to be encrypted, mostly double braided screens; twisted-pair cables are also used for video transmission, but the twisted-pair cables must be patch cords for network systems. Electrical sample on the cable.

Second, anti-theft alarm system Based on the professional bus form of the alarm system is currently the most widely used, the use of cable is also the most complex, so this is the focus of discussion.

The AVVR 2X0.3 (signal line) and AVVR 4X0.3 (2-core + 2-core power) cables are commonly used between the front-end detector and the alarm controller, and the general use between the alarm controller and the terminal security center is also 2-core signal line, as for the use of shielded or twisted-pair or ordinary sheath line, it needs to be determined according to the requirements of various brands of products, the size of the cross-sectional area is determined according to the distance and quality of the alarm controller and the center, but First of all, we must determine the location of the security center and the distance of each alarm controller. The longest distance can exceed the length specified by various brands. Otherwise, it will not meet the requirements of the bus regulations. The entire alarm area is relatively large, and the bus certainly does not meet the requirements. Under the conditions, the alarm can be divided into several areas. Each area determines the installation location of the sub-control center, to ensure that the bus within the area meets the requirements, and to determine the location of the general management center and the location of the sub-management center, determine the sub-control center to The communication mode of the management center adopts RS 232-RS 485 conversion transmission or uses RS 232 TCP/IP to use the integrated wiring system of the cell to transmit or divide. Management Center management software uses TCP / IP network forwarded to the General Administration Center.

The power supply of the alarm controller generally uses local power instead of the control room to provide centralized power. The line is short, and generally RVV 2X0.5 or higher specifications can be adopted, and the configuration is based on the actual line loss. Perimeter alarms and other public area alarm devices generally use a centralized power supply mode. The line is long and generally uses RVV 2X1.0 or higher specifications. Based on the actual line loss configuration, the grounding of the power cables used must be uniform.

Alarms of different natures (such as perimeter alarms, public area alarm buses, and household alarm buses are separated) should not use the same bus distribution box. The installation location should be easy to operate. A high-quality branching port is used to handle the connection between the bus and the bus to facilitate maintenance. For debugging, it is recommended that the bus and other lines be routed separately. When the bus is weak, the bridge needs to be kept at a distance according to the weak standard and other lines so as not to cause audio lines and other high- and low-frequency interferences of the unshielded twisted pair of the video intercom system, for example.

Third, the building intercom system At present, the cables used in the building intercom system are mostly RVV, RVVP, SYV and other types of cables, their performance is: transmission of voice, data, video images, and cable requirements Also reflected in the quality of voice transmission, data transmission rate, video image transmission quality and speed, so in the building intercom system, the quality of the cable used is still relatively high. The cable that transmits voice signals and alarm signals mainly uses RVV 4- to 8-core 1.0mm2 cables. In video transmission, cables are mainly based on SYV-75-5. Certainly, some network cable transmissions are also included. The new technology of video signal, no need for video lines, some systems are afraid of external interference or can not be grounded, the cable used in the system must use RVVP class.

With the constant improvement of the intelligence of the community, the demand for cables is getting higher and higher, and the cable contained therein has five types of lines, RVV signal lines,

Video line and so on.

Visual intercom systems use more complex lines. Here we will introduce visual intercom systems.

Direct-push-button video intercom system line standard: Each indoor unit's video, two-way audio and remote unlocking terminals are connected in parallel with the door machine by bus, but each call line is directly connected to the door machine. Therefore, there are many cables used in this type of multi-residential video intercom system. Video coaxial cables SYV-75-5, SYV-75-3 series, microphones/speakers/unlocking wires use a 4-core unshielded or shielded. Sheathed cable (AVVR/RVV/RVVP, etc.), power cord with a 2-core sheath cable (AVVR/RVV, etc.), call line with 2-core shielded cable (RVVP).

Digital coded push-button video intercom systems are generally used in multi-residential applications in high-rise residential buildings. According to different manufacturers of equipment system wiring standards are different, but the general system of basic wiring: the main line includes video coaxial cable (SYV-75-5, SYV-75-3, etc.), power cord (2-core AVVR or RVV, etc. ), audio/data control lines (4-core RVVP, etc.), household control lines (6-core RVVP, etc.).

Most of the residential buildings where the building’s visual intercom system is installed have a management center machine, and a community perimeter wall machine is installed at the entrance to the perimeter wall of the community to allow residents, management centers and visitors to implement technical so-called three-way calls. The wiring of such a networked system increases the interconnection lines between the cell door machine, the cell door machine and the management center machine, and generally includes a video coaxial cable (SYV-75-7, SYV-75-5, SYV- 75-3, etc.) Transmit video signals, 4-core shielded cable (RVVP 4X0.5, etc.) to transmit audio and control signals.

With the development of the market, many kinds of multimedia cable products have been trial-produced and produced by a number of wire and cable manufacturers with certain R&D capabilities, such as video power supply integrated lines for CCTV systems, including video and voice for video intercom systems. , VGA, VGA cables and other products used in projection systems, or products specially developed based on actual system requirements can play a significant role in saving wiring time and reducing system cost.