In important places such as money, gold, silver, underground record storage, etc., if a fraudster suddenly sneaks in. the burglar alarm will immediately sound red lights flash. Sirens were continuously ringing in the ear to alert people of abnormal conditions to take safety measures quickly.
Burglar alarm bells can automatically alarm because they are fitted with an infrared sensor and an automatic alarm device.
The temperature of all types of objects, higher than -273 ° C, can emit infrared rays. One has body temperature, which is no exception. Therefore, once a thief enters the area of the thief realm, infrared rays emanating from the thief’s body, through the lens in the condenser infrared sensor and photoelectric converter plate, are formed up infrared electrical pulse signal with a frequency of 0.5 – 20 Hz.
The amplification of the amplifier will greatly increase after the intensity is greatly increased. The signal will trigger the audio-frequency oscillator’s operation, transmitting an acoustic-frequency signal of 10 kHz. It is then modulated in a 49.7 MHz ultra-high frequency generator via transmitted radio waves. The ultra-high-frequency receiver is located in the center of receiving that radio wave. The ultra-high frequency elimination process emits 10 kHz audio signals and emits very harsh tones through the speakers.
Simultaneously, the power supply of the red warning light is also connected, immediately flashing continuously. The synergistic sound and light, effective automatic warning, work to prevent theft.
But this type of sensor requires to be installed at an altitude of about 2 m from the ground and must have a downward angle of view of about 15 ° to the ground to receive infrared rays from the human body sensitively emitted. Also, keep away from heat and direct sunlight.
There is also a burglar warning, which can actively emit modulated infrared rays, which shine directly on where the theft room is needed. Once a fraudster enters, he will mask the infrared ray, cause the infrared sensor to have no switching output of electrical signals, immediately start the alarm circuit, in the speaker emit an alarm. Bright, and at the same time, red light is flashing, using sound and warning light.
Among the automatic alarm devices designed specifically for home theft prevention, there is also a computer installed. Once a fraudster breaks into the realm of real estate, the infrared sensor immediately transmits an electrical signal, feeds it into a computer, connects to an automatic dialer. Uses a pre-recorded voice to call texting or mobile phone of the owner outside the house while calling preset alarm number to police headquarters.