There are mainly two types of signal transmission in closed-circuit television monitoring system: one is analog video signal, the transmission path is from camera to matrix, matrix to display or video recorder; the other is that digital signal includes control information between matrix and camera Transmission, digital signal in the computer part of the matrix. General equipment as a source of interference is unlikely, so interference mainly through the signal transmission path into the system.
CCTV camera monitoring system signal transmission path is through the video cable and twisted pair transmission control signal into the system interference are: a variety of high-frequency noise such as large inductive load start and stop, ranging from the introduction of ground frequency interference Balanced transmission line imbalance makes the noise suppression ability reduce the common frequency interference into differential mode interference. The impedance mismatch on the transmission line causes the signal reflection to deteriorate the signal transmission quality. Electrostatic discharge enters the device along the transmission line to cause damage or damage to the interface chip. Specific performance is as follows:
Effects due to impedance mismatch appear as ghosting on video images. In the signal transmission line will be formed in the pulse sequence before and after the edge of oscillation. The existence of the oscillation makes the threshold difference between high and low levels smaller. When the amplitude of the oscillation is big or there is other interference introduced, the pulse level can not be resolved correctly, resulting in longer communication time or communication interruption. Grounding and poor shielding can cause the transmission line to reduce the ability of external electromagnetic interference reduction, reflected in the video image is snow noise, moire interference and stripes rolling, etc .; spikes in the signal transmission line interference, resulting in communication errors. Balanced transmission line imbalances can also cause spikes on signal transmission lines. In addition to electrostatic discharge can cause damage to equipment, but also affect the memory of the data, the device appeared some inexplicable error.