What is a Body Alarm?

An alarm is a device that issues an alarm signal. Signals for forecasting, alerting and disarming. ^[1] Air defense alarm refers to the alarm system installed during the war to prevent enemy air strikes. It is an important part of urban air defense engineering. It is an alarm to alert people when the city is threatened by air strikes.

[jng bào qì]

An alarm is a device that issues an alarm signal. Signals for forecasting, alerting and disarming. ^[1]

According to the sound principle, there are:

1. Electric alarm: convert electrical energy into mechanical energy, and then convert mechanical energy into acoustic energy.

2. Electro-acoustic alarm: The small audio signal is converted into sound energy after being amplified by low-frequency power. That is, electronic energy is converted into sound energy.

3. Pneumatic alarm: convert electrical energy into mechanical energy, and then convert mechanical energy into pneumatic energy. From gas energy to

Infrared transmitter driver

Widely used in perimeter prevention, urban security, villa courtyard walls, residential perimeter,

The transmitter and receiver are located at different positions into an opposing installation method and a reflective installation method. The receiver of the reflective installation method does not directly receive the infrared beam emitted by the transmitter, but receives

The railings on the stone steps inside and outside the gates of the Forbidden City. If you look closely, you will find a spherical sculpture on the top of the column, all in the shape of a flower head, and a few holes outside the door near the top are all punctured. This kind of thing is called "Shibiela", also known as "Shi Haixiao", which is an ancient siren for alarm. Whenever a foreign enemy invades, war alarms, or fire, the guard will blow a small hole in the stone ball with his mouth. The stone ball will emit a whistle-like siren sound, and the thick and bright sound will spread throughout the Forbidden City. . When this alarm was created and how to blow it, very few people knew it, and it was limited to the Bannermen who were pro- or guardians, and the eunuch's guard eunuch.