How does the cable anti-theft alarm

Power carrier communication monitoring system anti-theft. Power carrier is a concept derived from the interdisciplinary discipline of power and communication. The power carrier communication method uses the signal transmission method in the wire and cable anti-theft system to load the detection carrier signal on the cable in the detection range, and the alarm in the monitoring center is connected to the carrier signal on the monitored cable. Once the cable goes out of the section, the signal transmission is interrupted. If the alarm fails to receive the signal, it will automatically alarm and play a warning role. The power carrier communication method is currently the most widely used anti-theft method, because it transmits the carrier signal on the monitored cable and does not require additional lines. Therefore, the power carrier communication method has the advantages of simple installation, concealed detection, and wide monitoring range ( Up to several kilometers) and other advantages. However, when the cable is stolen, only the alarm cannot be used to deter criminals, and video evidence cannot be collected. The single power carrier communication is facing the challenge of integration and systemization.

Capacitance detection monitoring system anti-theft. The principle of the capacitance detection method is to use a pair of vacant cables to short-circuit the cable terminal first, and the other end is connected to the multivibrator of the alarm. When the cable works normally, the oscillator of the alarm does not vibrate; The cable becomes a simple capacitor, and the oscillator will output a signal to cause an alarm, and the frequency of the oscillator output signal varies with the position where the cable is cut. It is the basic model of capacitance detection method.

Current detection type monitoring system anti-theft. The system judges the integrity of the cable system by detecting whether there is a transmission current in the cable loop on-line. That is to say, when the cable is working normally, the detection system has no response; when there is no current transmission in the cable, the detection system will activate the alarm system. The current detection system cannot be used in a cable anti-theft system with voltage but no current, such as power cables for blowers in subway tunnels or highway tunnels. In addition, the system will only alarm when all the branch cables of the circuit system are cut off (because the total current of the cable loop is zero when all the cable branches are disconnected). Therefore, the current detection type monitoring system has the hidden danger of "alarming but not reporting".