Twisted Pair (TP) is a widely used type of cabling consisting of two insulated wires that are twisted together according to specific standards, typically wound in a clockwise direction. It serves as a fundamental transmission medium in information and communication networks. Historically, twisted pair was primarily used for analog signal transmission, but it has since evolved to support digital signals as well. When installing or using twisted pair cables, there are several important considerations to keep in mind:
First, the twisted pair must comply with national product specifications. The cable should be made of pure copper, with a wire diameter of 0.5 mm². The resistance per 100 meters for a single core should be around 9.38 ohms, and for a full box (305 meters), it should not exceed 28 ohms—ideally no more than 30 ohms. The twisting density must meet the five-wire standard, and the cable must have sufficient flexibility and flame retardancy to pass national testing requirements.
Second, if the twisted pair is to be used outdoors, it is essential to choose an outdoor-grade, waterproof version to protect against moisture and environmental damage.
Third, during installation, care must be taken to avoid placing the twisted pair near high-voltage cables or equipment. It should also not be run alongside frequency converters or communication signal generators, as these can cause interference.
Fourth, each of the four pairs in a twisted pair cable can carry a separate signal. This allows for simultaneous transmission of video, audio, control signals, and even power. For example, a DC12V power supply can be used within 150 meters, while AC24V control signals can travel up to 300 meters. Signal transmission distances can extend up to 1,000 meters depending on the application.
Fifth, both active and passive devices often come with built-in surge protection, so proper grounding is essential. If installed outdoors, the system can be grounded along with the camera, and the grounding resistance must be below 4 ohms to ensure safety and performance.
Lastly, the video line from the camera to the transmitter should be as short as possible to maintain stable and high-quality signal transmission. By following these guidelines, you can ensure optimal performance and longevity of your twisted pair cabling system.
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