The power line carrier communication uses the power line as the transmission channel, and has the advantages of high channel reliability, low investment, quick effect, and synchronization with the power grid construction. All equipment in the system can be connected to the power line nearby, without rewiring to damage the building structure and decoration. It has the characteristics of an old building that is suitable for early communication systems and does not occupy other resources. At the same time, it can inspect users and discover hidden dangers in time. It is good for finding the cause of the accident. The disadvantage is that it is limited to the management within the power supply range of a single transformer, and the design beyond the power supply range of the transformer is complicated and the cost is high. With the improvement of living standards, intelligent buildings and intelligent communities have become hot spots in the market. As a comprehensive system engineering, it contains many small systems. There are also problems in laying communication lines in each household and every room, such as fire alarm system and anti-theft alarm system. The information of each alarm point is centralized and processed uniformly, and the power line carrier communication has its incomparable superiority. Since the community itself has a community service and security center, it can obtain relevant alarm information and regularly patrol the user in the first time. If necessary, you can contact the superior alarm center by telephone contact, which can fully compensate for the shortcomings of power line carrier communication. This section takes the application of the intelligent community security alarm network system as an example to introduce the power line carrier communication system based on LM1893. Power line carrier communication modulates the carrier communication signal on the transmission line. The attenuation characteristic of the carrier channel is similar to the overhead bright line. That is, the higher the frequency, the greater the attenuation. Therefore, the transmission frequency band is generally selected in the range of 40 to 500 kHz (in the middle frequency band), and the coupling between the power line and the end station is performed by the coupling capacitor. Further, in order to prevent the carrier communication signal from flowing to various power devices, a choke coil is disposed. The structure of the intelligent community communication alarm system is shown in Figure 1-157. The hardware circuit block diagram of the regional control center is shown in Figure 1-158. The central equipment adopts 51 single-chip microcomputer as the main control unit, and realizes communication with each user terminal, transmission alarm and inspection information through the power line carrier chip LM18 93. Mini Power Bank,Small Power Bank 10000mah,Mini Power Bank for Iphone,Power Bank Mini Pogo Technology International Ltd , https://www.wisesir.net
