In traditional security monitoring systems, image interference is a common issue that often fails to meet acceptance standards, causing significant challenges during the project commissioning process. This paper explores how the application of common cable transmission technology effectively addresses various types of interference, focusing on both the causes and solutions.
First, let's understand the sources of image interference. Generally, interference can be categorized into three main areas: connections, equipment, and transmission.
Interference from connections typically manifests as "crossing," "distortion," or flickering. These issues can usually be resolved by remaking BNC connectors. When interference arises from devices such as matrix switches or distributors, it may result in misaligned images or weak signals. In most cases, replacing the faulty device solves the problem.
However, the most challenging type of interference comes from the transmission process itself. Common forms include electromagnetic interference, potential difference interference, AC power interference, and damage to cables.
Electromagnetic interference is the most frequent issue in video surveillance. It occurs when video cables pass near large power equipment, high-voltage substations, or motors, which generate strong electromagnetic fields. This can cause visual distortions like "crossing," "corrugation," or random spots on the screen. Such interference is commonly found in industrial plants, elevators, stations, and other environments with heavy electrical activity.
Potential difference interference happens when different parts of the system have varying electrical potentials. For example, if a camera is powered by one transformer while the control room uses another, the mismatch can lead to image distortion. This is especially common in large-scale installations like campuses or urban monitoring systems.
AC power interference is another major concern. Although centralized power supply is recommended for stability, AC220V power lines can still interfere with video signals, especially when they are bundled together with video cables. The resulting interference often appears as vertical stripes moving up and down on the screen.
Cable damage interference occurs during installation, particularly when multiple cables are twisted or pulled forcefully. This can damage the insulation or shielding, leading to signal cross-talk and visual artifacts like "drawing" or "slanted points." This issue is more prevalent in densely populated monitoring setups.
Now, let's explore how common cable transmission helps mitigate these problems. By transmitting signals at higher frequencies (47 MHz to 860 MHz), the system avoids the lower frequency range where most interference occurs. This significantly improves signal integrity and reduces the impact of electromagnetic and motor interference.
Common cable transmission also eliminates potential difference issues. Since the shielding is grounded and only the copper core carries the signal, potential differences between ends do not affect the video signal. This is similar to how cable TV systems operate across regions without experiencing such disturbances.
Regarding AC power interference, the signal is modulated to frequencies above 50 MHz, where AC power interference is negligible. This ensures a cleaner video signal.
Finally, using a single cable for multiple channels reduces the number of cables needed, minimizing the risk of physical damage during installation. This approach not only simplifies wiring but also reduces human error, leading to fewer signal disruptions.
In conclusion, the use of common cable transmission is an effective and efficient solution to reduce various types of interference in video surveillance systems. By addressing the root causes and avoiding interference-prone areas, this method offers a reliable and scalable approach worth adopting.
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Editor: Hardware Business Network Information Center
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