The purchase of the security industry video monitor cable
At present, at the same time, the domestic security cable enterprise in the industry order continuous norms, the market environment is gradually health, constantly improve their own strength and continuously extend the product and service, security cable industry as refreshing as China security industry, will be the vigorous development, let us join hands together to the security, the prospect is bright industrial deepening.
Choose the video monitor cable
Video signal transmission generally use the direct modulation technique, using baseband frequency (about 8MHz bandwidth) form, the transmission medium is the most commonly used coaxial cable. Coaxial cable is specially designed for the transmission of the video signal, its frequency loss, image distortion, image attenuation amplitude is relatively small, can be very good to complete the task of transmitting video signal.
The general use of dedicated SYV75 OHM Series coaxial cable, commonly used models for SYV75-5 (it on the video signal transmission distance is generally 300-500m);
The distance is far, need to use coaxial cable SYV75-7, SYV75-9 or even SYV75-12 (in practical engineering, thick cable no relay transmission distance can reach more than 1km);
There are also by adding video amplifier to enhance video brightness, chroma and synchronous signal, but the line interference signal will be amplified, so the circuit is connected in series video amplifier cannot too much, can appear otherwise saturation is like, cause image distortion;
Further distance using fiber optical transmission system, optical fiber transmission with small attenuation, wide frequency band, from a series of advantages of electromagnetic wave interference, light weight, good secrecy, mainly used for national and provincial and municipal backbone communication network, cable TV network and high speed broadband computer network. In closed-circuit television monitoring system, optical fiber transmission has become the preferred way long distance video and audio signal transmission and control.
The video signal can also use the twisted pair transmission, it must use the twisted pair transmission equipment. In some special applications, twisted pair transmission equipment is essential. Such as: when the building has according to the integrated wiring standard laid a lot of twisted pair (standard that the three lines or five lines) and the related room left in the corresponding information interface (RJ45 or RJ11), then add the closed-circuit television monitoring equipment is not required to re wiring, video and audio signals and control the signal can be transmitted through a twisted pair, wherein the transmission of the video signal will be used twisted pair transmission equipment. In addition to the already equipped with a twisted pair (or two core sheathed wires) and the need to be applications to image the front camera control room equipment, also need to the twisted pair transmission equipment.
Twisted pair video transmission equipment function is in the front end will be suitable for the non balanced transmission (i.e. for 75 ohm coaxial cable transmission) conversion of video signal suitable for transmission (i.e. balanced twisted pair transmission) of the video signal is processed with the front end; the opposite at the receiving end, the video signals through the twisted pair came back converted into a video signal and non equilibrium.
Twisted pair video transmission equipment has the function of amplification, and is also suitable for signal transmission in long distance. The above different transmission mode, transmission parts and transmission lines use are quite different.
Imaging device with electric pan, electric lens in the configuration for communication cable, when in use, need to install the remote control decoder in the field. Communication cable between the video matrix switch hosts the decoder and the control center, using 2 general core shielded communication cable (RVVP) or a category 3 twisted pair UTP, each core cross-sectional area of 0.3mm2 ~ 0.5mm2. Basic principles for selection of communication cable is the longer the distance, the greater the diameter of line. For example: basic communication distance RS-485 communication rules is 1200m, but the selection of RVV2-1.5 sheathing line in practical engineering can be extended to the communication length more than 2000m. When the communication distance is too long, need to use the RS-485 communication repeater.
Control cable is usually refers to the control console for multicore cables and electric variable lens, PTZ, it connected to the controller or the decoder electric lens control terminal, the other end is directly connected to the corresponding terminals, electric pan tilt of the lens.
Because the control cable is provided by the DC or AC voltage, and the general distance is very short (sometimes less than 1m), basically interference problem does not exist, so do not need to use the shielded wire. Control cable used mostly adopts the 6 core or 10 core cable, such as RVV6-0.2, RVV10-0.12 etc.. The 6 core cable are respectively connected to the tripod head upper and lower, left and right, automatic, public 6 terminals, 4 zoom, focus, aperture, the common terminal 10 core cable in addition to the 6 terminal is connected with the PTZ also includes electric lens.
In closed-circuit television monitoring system, from the decoder to PTZ and lens control cable due to the relatively short distance generally is not required; controller with control room to PTZ and lens distance is less a few meters, more than several hundred meters, to control cable needs to have certain requirements, namely the wire diameter to rough, such as the selection of RVV10-0.5, RVV10-0.75 etc..
Sound monitoring cable generally use 4 core shielded communication cable (RVVP) or a category 3 twisted pair UTP, each core area of 0.5mm2. In the absence of interference environment, also optional for unshielded twisted pair, such as commonly used in integrated wiring in the category 5 unshielded twisted pair (4 to 8 cores); the audio signal monitor head in a monitoring system to control room is used point to point wiring way, with high voltage and small current transmission, so use 2 core cable can be non shielding, such as RVV2-0.5 etc..