The transmitter and the receiver are arranged in different positions, which are divided into opposite-type installation and reflective installation. The receiver of the reflection-type installation is not directly receiving the infrared beam emitted by the transmitter, but is received by the reflector or the appropriate reflection. The infrared beam reflected by the object (such as the lime wall and the paint layer with a smooth door surface). An alarm signal is issued when the position and direction of the reflective surface are changed or one of the infrared-emitting light beam and the reflected light beam is blocked so that the receiver cannot receive the infrared-reflected light beam.
Widely used in perimeter prevention, urban security, villa walls, community perimeter, factory warehouses, companies, schools, homes, warehouses, resources, oil and many other fields.
The railings on the stone steps inside and outside the Forbidden City, if you look closely, will find a spherical carving on the top of the column, all of which are flower-headed, and several of the holes near the doorway have holes pierced at the top. This kind of thing is called "Stone Bela", also called "Shi Hai Xiao". It was an ancient siren used for alarm. When encountering invading foreign enemies, war alarms or fires, the guards used mouthpieces to blow holes in the stone balls, and the stone ball clubs issued siren-like sounds of sirens. The loud and clear voice spread throughout the Forbidden City. . When the sirens were founded and how they were blown, there were very few people who knew about them. They were limited to the flag bearers who had been pro-military or military guards, and the guardian eunuchs of the inner court.