Video signal transmission generally adopts direct modulation technology and takes the form of baseband frequency (about 8MHz bandwidth). The most commonly used transmission medium is coaxial cable; coaxial cable is specially designed to transmit video signals, and its frequency loss, image distortion, The amplitude of image attenuation is relatively small, which can well complete the task of transmitting video signals.
Commonly used special SYV75 ohm series coaxial cable; commonly used model is SYV75-5 (its non-relay transmission distance for video signals is generally 300-500m); when the distance is long, SYV75-7, SYV75-9 must be used Axle cable (In actual engineering, the relayless transmission distance of the thick cable can reach 1km or more)
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 when in use; a communication transmission cable between the on-site decoder and the video matrix switching host in the control center is generally adopted. 2-core shielded communication cable (RVVP) or Cat. 3 twisted-pair UTP with a cross-sectional area of â€‹â€‹0.3mm2 to 0.5mm2 per core; the basic principle for selecting a communication cable is the longer the distance and the larger the wire diameter; the basic RS-485 communication requirements The communication distance is 1200m, but in the actual project, the RVV2-1.5 sheath line can be used to extend the communication length to over 2000m.
The control cable usually refers to the multi-core cable used to control the PTZ and the electric variable lens; one end of the control cable is connected to the PTZ of the controller or the decoder, and the electric lens controls the terminal, and the other end is directly connected to the PTZ. On the corresponding terminals of the electric lens, the control cable provides DC or AC voltage, and the distance is generally short (sometimes less than 1m). There is basically no interference problem, so no shielded cable is required.
Commonly used control cables mostly use 6-core or 10-core cables, such as RVV6-0.2, RVV10-0.12; 6-core cables are connected to the top, bottom, left, right, automatic, and public 6 terminals of PTZ respectively, 10 cores In addition to the six terminals of the pan-tilt head, the cable includes four zooming, focusing, aperture, and common terminals of the electric lens; in the monitoring system, the control cable from the decoder to the pan/tilt head and the lens is short due to the short distance. Generally do not make special requirements; from the central control room controller to the pan and tilt and electric lens distances ranging from tens of meters, as many as several hundred meters, the control cable needs to have certain requirements, that is, the diameter of the wire should be thick, such as selection RVV10-0.5, RVV10-0.75
Audio monitoring cables generally use 4-core shielded communication cable (RVVP) or Category 3 twisted pair UTP, with a cross-sectional area of â€‹â€‹0.5 mm2 per core.
The audio signal of the monitor head in the monitoring system is transmitted to the central control room and is a point-to-point wiring method. It is transmitted with high voltage and low current, so unshielded 2-core cable can be used, such as RVV2-0.5.
RVV2*0.3 (signal line) and RVV4*0.3 (2-core + 2-core power) cables are generally used between the front-end detector and the alarm controller; the 2-core is generally used between the alarm controller and the terminal security center. Signal line
Whether the signal line is shielded or twisted or it is a common sheathed cable, it needs to be determined according to the requirements of various brands of products; the rough specification of the signal line diameter is determined according to the distance and quality of the alarm controller and the center; alarm control The power supply of the device generally uses local power instead of centralized power supply in the control room. The line is short, generally adopting RVV2Ã—0.5â€ or more specifications; the perimeter alarm and other public area alarm devices generally use centralized power supply mode, and the line is longer. Use RVV2*1.0" or above specifications
Cables used in building intercom systems are mostly cables such as RVV, RVVP, SYV, etc.
Has: transmission of voice, data, video images, while cable requirements also expressed in the quality of voice transmission, data transmission rate, video image transmission quality and speed, etc.
Cables that transmit voice signals and alarm signals mainly use RVV4-8*1.0
Video transmission is based on SYV75-5 cable
Some systems must use RVVP cables in the system when they are afraid of external interference or cannot be grounded.
Direct Push-to-Talk Visual Intercom System Line Standard:
Video terminals, two-way audio and remote control unlocking terminals of all indoor units are connected in parallel with the door machine by bus, but each call line is directly connected to the door machine alone.
--Video coaxial cable SYV75-5, SYV75-3
- Use a 4-core unshielded or shielded sheath cable (AVVR4, RVV4, or RVVP4, etc.) for the microphone/speaker/unlock cord
- A 2-core jacket wire (AVVR2, RVV2, etc.) for the power cord
-- 2-wire shielded cable for call lines (RVVP2)
Digital coded push-button video intercom system:
- The main line includes video coaxial cable (SYV75-5, SYV75-3, etc.)
- Power cord (AVVR2, RVV2, etc.)
-- Audio/data control lines (RVVP4, etc.)
- Household Signal Line (RVVP6, etc.)
Nail Picking,Stainless Steel Nail Snips,Screw Shank Nail Stainless Steel,Carbon Steel Nail Clipper
YANGJIANG TRI-WIN INDUSTRY & TRADE CO.,LTD , https://www.triwintableware.com