A detector uses sensors to sense various physical and chemical changes and generate signals such as currents and pulses to drive the RF circuit to emit alarm signals.

The host is the core of the system. It is used to receive alarm signals from detectors and provide timely feedback; After receiving the alarm signal, the host will generate a high decibel alarm sound and use the telecommunications network to dial multiple sets of alarm numbers set by the owner.

Passive infrared detectors rely on the passive absorption of thermal energy and the infrared heat emitted by the body during animal activity to sound an alarm, also known as pyroelectric infrared probes. The detector itself does not emit infrared radiation

Why can passive infrared detectors generate alarm signals when people are moving within the alert range?

In nature, any object above temperature (-273 degrees) will produce an infrared spectrum, and the wavelength of the infrared energy released by objects at different temperatures is different. Therefore, the infrared wavelength is related to the temperature.

According to the transmission method of alarm signals, there are two types: wired and wireless. After detecting illegal intruders, the detector transmits alarm signals to the alarm host in two ways. Wireless detectors transmit alarm signals by emitting electromagnetic waves of a certain frequency, while wired detectors are divided into switch signal output and level signal output.

There are two key components in passive infrared detectors, one is the pyroelectric infrared sensor (PIR), which can convert infrared signals with wavelengths between 8-12 μ m into electrical signals and suppress white light signals in nature. Therefore, in the warning area of passive infrared detectors, when there is no human movement, the pyroelectric infrared sensor only senses the background temperature. When a human enters the warning area, through the Fresnel lens, the pyroelectric infrared sensor senses the difference signal between the human body temperature and the background temperature. Therefore, the basic concept of infrared detection in infrared detectors is to sense the temperature difference between moving objects and background objects. Another device is the Fresnel lens, which has two forms: refractive and reflective. The Fresnel lens has two functions: one is the focusing effect, which refracts (reflects) the pyroelectric infrared signal onto the PIR, and the other is to divide the alert area into several bright and dark areas, so that moving objects entering the alert area can generate a changing pyroelectric infrared signal on the PIR in the form of temperature changes, so that the PIR can produce a changing electrical signal.

Active infrared anti-theft detector

The transmitting end actively emits infrared radiation, and the receiving end receives the infrared radiation, forming a network of infrared radiation. This detector can actively prevent intruders and will not generate false alarms due to the passage of small pets or the influence of climate, thus greatly reducing the false alarm rate.