October 09, 2023
Introduction to video surveillance cable types:
Depending on material, there are two types: SYV and SYWV. The physical structure of material of insulating layer is different. SYV is a rigid polyethylene cable; SYWV is a high physical performance foam cable. foam cable is better than polyethylene cable. (S-coaxial cable Y-polyethylene V-polyvinyl chloride W-stabilized polyethylene)
According to impedance, it can be divided into SYV 50-XX SYV 75-XX SYV-100 XX...XX is outer diameter of insulation layer.
1. Composite video signal: common interface - BNC, RCA (lotus head)
75 indicates resistance and next 3 and 5 indicate outside diameter of insulation (3mm/5mm).
Video line points:
The transmission range of 75-3 is about 200 meters;
The transmission range of 75-5 is about 500 meters;
Transmission range at speed 75-7 is about 500-800 meters);
The transmission range of speed 75-9 is about 1000---1500 meters;
The transmission range of 75-12 speeds is about 2000----3500 meters.
2. S-terminal (or Y/C)
Its scientific name is "two-piece video interface", commonly known as S-terminal, and transmission distance is only 15 meters.
The S-Video connection specification is a specification developed by Japanese. S stands for "SEPARATE (separation)", which separates luma and chrominance output data, avoiding confusion of luma and chrominance when outputting mixed video signals. together. The S interface is actually a five-wire interface that consists of five main wires, including two luminance signals, two video chrominance signals, and one common shielded ground wire.
Compared with AV interface, since it no longer performs Y/C mixed transmission, it does not need to perform bright color separation and decoding, and use of separate transmission channels can largely avoid signal transmission to video equipment. Image distortion caused by crosstalk , greatly improve image clarity. However, S-Video still needs to mix two channels of chrominance signals (Cr Cb) into one channel of chrominance C signal, transmit it, and then decode to Cb and Cr on display device for processing, which will still yield a certain amount signal loss Distortion (slight but still noticeable when tested on strict broadcast quality video equipment). Moreover, due to mixture of Cr and Cb, bandwidth of chrominance signal is also limited to a certain extent, so although S-Video is already relatively good, it is still far from perfect. Although S-Video is not best, considering other factors such as current market conditions and total cost, it is still one of most widely used video interfaces.
3. VGA Signal
VGA (Video Graphics Array) is a video transmission standard introduced by IBM with PS/2 computer in 1987. It has advantages of high resolution, fast display speed and rich color saturation. It is widely used in color display field, application, but it is easy to weaken, transmission distance is short, and it is easy to interfere. Its 3+4/6VGA transmission range is 15-30m.
4. Component video (RGBHV signal)
The color difference interface is based on S interface, and sends blue (b) and red (r) difference in chrominance (C) signal separately, and its resolution can reach more than 600 lines. It usually uses two logos YPbPr and YCbCr, former means progressive color difference output, latter means interlaced color difference output. Nowadays, many TV products rely on component input to improve quality of input signal, and various levels of signals can be input through component interface, from simplest 480i to 480p multi-scan, even 720p, 1080i, etc. There is no way to send a signal to a TV via component input. The transmission distance of 75-2RGB is 30-50m, and transmission distance of 75-3RGB is 50-70m.
DVI-A interface (analogue, analog): This interface is actually a deformation of VGA interface. It used to be mostly used on some high end CRT monitors but has now been largely abandoned. We often say "fake DVI" refers to DVI-A because it still carries analog signals instead of digital ones, reflecting benefits of DVI technology.
DVI-D (Digital, Digital) Interface: DVI-D is literally a digital signal interface, more advanced than DVI-A; interface may not be compatible with older CRT monitors. that there is only a D-Sub interface on LCD monitor, then user will only stare stupidly.
DVI-I (Integrated, Integrated) interface: This is a hybrid interface that combines DVI-A and DVI-D. It is compatible with DVI-D and DVI-A (via an adapter. It can also be converted to D-Sub), which is most compatible DVI interface
Generally speaking, when transmitting video signals with resolutions lower than 1600×1200 at 60Hz, there is no obvious difference between using single-link DVI and dual-link DVI. If your monitor supports Full HD (1920×1080) resolution or higher, do not select a single link DVI data cable. DVI-D can only receive digital signals, DVI-I can receive digital and analog signals at same time, and transmission distance is short, 7-15m.
Using same basic protocol as DVI digital signal, it can also be replaced by DVI signal through an adapter and is compatible with DVI signal. What's more powerful than DVI interface is that HDMI allows high-quality audio signals to be passed through HDMI cables while developing communication protocols. The seamless connection reduces connection issues and makes HDMI more compatible. Support 5Gbps data rate, maximum transmission distance is 15 meters.
Compared to DVI, HDMI can carry digital audio signals and extends HDCP support to provide enhanced additional DDC functionality. HDMI supports a data rate of 5 Gbps and can be transmitted up to 15 meters, which is enough to handle 1080p video and 8-channel audio. And since 1080p video and 8-channel audio require less than 4 GB/s, HDMI still has plenty of headroom. This allows you to connect your DVD player, receiver and PRR separately with a single cable. In addition, HDMI supports EDID and DDC2B, so HDMI devices are plug and play. The signal source and display device automatically "negotiate" and automatically select most appropriate video/audio format.
SDI (Serial Digital Interface) is "Digital Component Serial Interface". Then HD-SDI is a high definition digital component serial interface. HD-SDI is an uncompressed real-time high-definition broadcast camera, another technological breakthrough in security monitoring, and a device that provides high-definition image sources for monitoring center.
Second, control signal
General control signals, RS232, RS422, RS485, IR, CR-NET (CREATOR control signal)
RS232 baud rate is low. During asynchronous transmission, data rate is 20Kbps. The interface uses a signal line and a return signal line to form a common terrestrial form of transmission. This conventional terrestrial transmission is subject to common mode noise. , so anti-noise interference is weak. The transmission distance is 15 to 20 meters. When using a 150pF/m communication cable, maximum communication distance is 15m; if cable capacitance per meter decreases, communication distance can be increased. Another reason for short transmission distance is that RS-232 is a one-way signal transmission, which has problems such as general background noise and failure to suppress common mode interference, so it is generally used for communication within 20m.
RS-422 is a differential mode transmission with strong anti-interference capability, can transmit 1200 meters, and maximum transmission rate is 10Mbps. The length of a balanced twisted pair is inversely proportional to transmission speed, and maximum transmission distance can only be achieved at speeds below 100 kbps. The highest data rates are only available over very short distances. As a rule, maximum transmission rate that can be obtained over a 100-meter twisted-pair cable is only 1 Mbps.
The maximum communication distance of RS-485 is about 1219 meters, and maximum transmission rate is 10Mbps. The RS-485 interface uses a combination of a balanced driver and a differential receiver, which improves ability to resist common mode. dryness, that is, it has good noise immunity.
The transmission distance of IR (CREATOR central control IR) is 150 meters.
The transmission distance of CR-NET (CREATOR control signal) is 800 meters.