Cable as the infrastructure for the whole project in the transmission of signals at the same time, guarantee the normal operation of the system. Cable as the supporting facilities are widely used in all kinds of security subsystem, and increasing with the development of information technology and safety requirements, cable application, the application level is also increased.
Throughout the elv project construction, the cable is the most basic facilities, it is like the body's nerves and blood vessels, spread in the system. The more is take cover engineering, through the wall, tunneling, pipeline installation, at the same time of transmission signal, guarantee the normal operation of the system. At present, numerous cable products, in accordance with the purposes can be divided into bare wire, insulated wire, heat-resistant wires, shielded wires, power cables, control cables, communication cables, rf cable, etc.
In security systems, television monitoring, entrance guard controls, anti-theft alarm, public broadcasting, intelligent wiring and other kinds of subsystems cannot leave the cable connection, and with the awakening of people security awareness, cable as the supporting facilities are widely used in all kinds of security subsystem, and the development of information technology and safety requirements increasing, cable application, the application level is also increased. The most widely used in the security system mainly includes the communication cable, control cable, cable TV antenna, radio, audio cable, etc. And antiflaming fire-resistant, high temperature resistant low temperature resistance, low inductance, low noise, green environmental protection, low smoke zero halogen and a series of unique properties and the special structure of products is also more and more applied in the security system.
Below according to the cable is different, in the field of security system used in the classification is introduced.
Communication cables
Mainly used for close range of audio and digital communication, communication and long-range high frequency carrier type, type and specification is various, mainly including digital communication cable, the public line/telephone communication cable, multimedia cables, etc. Due to the public communication cable and multimedia cable is relatively simple, focus on digital communication cable here.
Digital communication cable is mainly used for building integrated wiring system and residential users in the workspace communication terminal and the transition between the wiring between distribution frame, suitable for 155 mbpsatm, 100 MBPSTP - PMD, 100 MBPS Ethernet, and other transmission rate of 622 MBPS system applications. The main is shielded twisted-pair cable and unshielded twisted pair, but is shielded twisted-pair cable price is higher, install complex, except in some for areas having a higher transmission quality requirements, general use a shielded twisted-pair cable.
Unshielded twisted pair (UTP) for the metal shielding material, only a layer of insulating rubber package, light weight, small volume, good elasticity, the price is relatively cheap, flexible network. According to the electrical properties of different, can be divided into three categories, five, five, six types of twisted pair.
Which three kinds of UTP adapted to the Ethernet (10 MBPS) to the requirements of transmission medium, is important in early network transmission medium; Five kinds of UTP low prices high quality become the medium of choice for fast Ethernet (100 MBPS), its logo is "CAT5, bandwidth of 100 m; Super five UTP is mainly used for one billion - bit Ethernet (1000 MBPS), six types of shielded twisted-pair cable can be very good support gigabit Ethernet, and realizes the transmission distance of 100 m, is widely used of wiring server room, although the price is higher, but with the ultra five types of cabling system has the very good compatibility, and able to support 1000 base-t is very good, is gradually become the latest must-haves in the integrated wiring.
Communication cables in the configuration is commonly used in electric yuntai, electric lens camera device, generally USES the core block communication cable (RVVP) 2 or 3 kind of twisted pair UTP, each core cross-sectional area was 0.3 ~ 0.5 was. Choose the communication cable is the basic principle of the longer the distance, the larger the wire diameter. RS - 485 communication rules, for example, the basic communication distance is 1200 m, but in the practical engineering chooses RVV2 1.5 sheathed wire communication can be extended to more than 2000 m length. When the communication distance is too long, need to use the RS - 485 communication repeater.
Security monitoring cable
It is mainly used for building and residential area monitoring equipment, including video transmission lines, power cables, signal control, etc.
Video transmission cable
Mainly adopts coaxial cable with twisted-pair transmission. Coaxial cable with solid copper body as the core, the outsourcing to knit mesh conductor surrounded by a layer of insulation materials, and covering a layer of protective materials outside the network. The loss frequency attenuation amplitude, image distortion and image is small, it is mainly used for transmission of video signal, in a small range of monitoring system, due to the transmission distance is very close, using coaxial cable transmission directly to damage the quality of the images is not big, can meet the practical requirements.
In monitoring and control system mainly adopts Ω, 75-5 coaxial cable, commonly used models for SYV75-5, the transmission distance is 300-500 - m, far away to needs the SYV75-7, SYV75-9 even SYV75-12 coaxial cable, can also be used by adding video amplifier in order to enhance brightness, chroma and synchronization of the video signal, but the line of jamming signal would also be amplified, too much so loop can't concatenated video amplifier.
But thicker, coaxial cable wiring is not very convenient, when it is applied in intensive monitoring and it can only transmit video signal, if the system need data transmission control, such as audio signal at the same time, you need to other wiring. Coaxial cable anti-interference ability is limited, cannot be used in strong jamming environment, at the same time, it is greatly influenced by climate change, the image quality will be affected by a certain accordingly. Therefore, in the process of video transmission, using twisted-pair transmission has become most people's choice.
In order to reduce the degree of interference signal, twisted-pair cable of each pair of twisted pair consists of two insulated copper wires twisted around each other, and the transmission distance, easy wiring, low prices. But if directly within the twisted-pair transmission, the decay will be very big, so the video signal on the twisted pair to realize long distance transmission, amplification and compensation must be conducted. To add a pair of twisted pair to transmit video after sending and receiving devices, can be to transmit the image to 1? 2 km, and twisted pair video transmission equipment cheap, does not increase the system cost.
The signal line
Usually refers to is used to control the haeundae and electric variable lens multi-core cable, provide more dc or ac voltage, within the scope of the short distance, using 6 or 10 core cable, as, RVV10 RVV6-0.2-0.12, etc. And is controlled by the controller to the yuntai and electric lens distance is less dozens of meters, more than a few hundred meters, the control cables will need to have certain requirements, namely the wire diameter to coarse, if choose RVV10 0.5, RVV10 0.75, etc.
The power cord
The power cord to use more at the connection between security equipment and power supply. Because usually connected to the power supply directly, have higher requirements on the withstanding capability of the cable. So far, but every square to the power cord can carry electricity flow, theoretically not clearly, it is generally believed in 2? 5 a. But according to use different environment, the service life of the power cord have bigger difference. If long time use, heat dissipation and is bad, you should try to choose large cross-sectional area of conductors. But there is no denying that in the same flow, with large cross-sectional area, only good, no harm.
Cable TV antenna
The more using coaxial cable, strong anti-interference ability, can choose to 5, 7, 9 coaxial cable, can be applied to below 1 GHZ closed-circuit system, community antenna system (CATV, MATV) as a main line and branch line, and other high frequency machine wire or internal wiring. Mainly according to the standard GY/T 135-1998 production, its internal have the aluminum foil shield, woven layer can be divided into 128, 96 and so on, weave a number of different, its coverage area is also different.
Broadcasting audio cable
Mainly used for speakers lines, amplifiers and audio equipment, low frequency, audio frequency signal transmission, widely used in public broadcasting, conference room, hall, background music, stage acoustics and sound engineering such as home multimedia system.
Mainly by the twisted bare copper conductor and PVC insulation, conductor cross-sectional area was 0.5 ~ 4 was, by stranded structure can make the wire soft, and high-fidelity audio. Because audio cables required to heat degree is higher, and under the condition of continuous work to also want to maintain a high real audio, so for the sake of their resistance to withstand high heat capacity, under the condition of continuous fever will maintain the performance in good use.
Special performance cable demand increase
In recent years, with the enlargement of the security market, antiflaming fire-resistant, high temperature resistant low temperature resistance, low inductance, low noise, green environmental protection, low smoke zero halogen has unique properties and special structure of products is also more and more applied in the security system.
With low smoke zero halogen cables used in fire protection requirements of high places, in the flame combustion produces little smoke, the release of gas does not contain halogen elements (low halogen), non-toxic (low), when the fire broke out, can greatly reduce the instrument and the harm of human body. According to zhejiang zhong an electronic engineering co., LTD. Technical director Chen Gulong introduced: "when the fire broke out, cable epidermis after burning exudes a poisonous halogen gas easily, easy to cause harm to human body, a lot of people is not burned in the fire, but this kind of halogen gas fume death, so some fire demanding place tend to use low smoke zero halogen and flame retardant fire-resistant cable."
While others have special properties of the cable with the special requirements of some areas gradually appear in people's life, become a generation to be bestowed favor on newly.
conclusion
Cables are small, but it is an integral part of security system, adjust measures to local conditions to choose the appropriate cable, to achieve the best transmission effect, lay the foundation for high quality projects.
