1. What parts does the alarm system consist of?

A simple alarm system consists of a front-end detector, an intermediate transmission part and an alarm control panel. For a large-scale alarm system, the detector and the alarm control panel can be regarded as the front-end part, the transmission part is between the alarm control panel and the alarm receiver, and the central alarm receiver and computer are regarded as the back-end part.

2. According to the different ways of information transmission, the alarm system can be divided into several types?

According to the different information transmission methods, it can be divided into two types: wired and wireless from the detector to the alarm control panel. From the alarm control panel to the central alarm receiver, it can also be divided into two types: wired and wireless. Among them, the wired system can also be divided into two types: line-based transmission and bus-based transmission. Wireless is via GSM, GPRS, 3G, 4G transmission.

3. What are the types of detectors?

According to the detection principle and working method, it can be divided into: PIR motion (infrared), microwave, infrared microwave composite, vibration, smoke, gas, glass breaking, ultrasonic, etc. Among them, PIR motion (infrared) detectors can also be divided into active infrared and passive infrared, and smoke detectors can also be divided into ion type and photoelectric type.

4. How does the active infrared detector work?

The active infrared detector consists of an infrared emitter and an infrared receiver. The infrared emitter emits one or more modulated infrared rays to the infrared receiver. When there is no obstruction between the transmitter and receiver, the detector will not alarm. When an object is blocked, the output signal of the receiver changes, and the detector alarms.

5. What is the working principle of passive infrared detector?

There are two key components in the passive infrared detector, one is the Fresnel lens and the other is the pyroelectric sensor. Any object with a higher temperature (-273°C) in nature will produce infrared radiation, and the wavelengths of infrared energy released by objects at different temperatures are also different. The human body has a constant body temperature, which differs from the temperature of the surrounding environment. When the human body moves, the change of the temperature of the surrounding environment is detected by the pyroelectric sensor through the Fresnel lens, thereby outputting an alarm signal.

6. How does the microwave detector work?

Microwave detectors use the principle of the Doppler effect. In the microwave section, when sending at one frequency, when the emitted microwave encounters a fixed object, the frequency of the reflected microwave remains unchanged, that is, f sending = f receiving, and the detector will not send out an alarm signal. When the emitted microwave encounters a moving object, the frequency of the reflected microwave will change, that is, f send ≠ f receive, and the microwave detector will send out an alarm signal at this time.

7. What is a dual-element infrared detector? What is a four-element infrared detector?

A detector with two detection sources that integrates two pyroelectric sensors with the same performance and opposite polarity is a binary detector. A detector with four detection sources that integrates four pyroelectric sensors with the same performance and opposite polarity is a four-element infrared detector.

8. What is the function of Fresnel lens?

Fresnel lenses serve several purposes.

The first is focusing, which refracts or reflects the pyroelectric infrared radiation onto the pyroelectric sensor.

The second is to divide the detection area into several bright areas and dark areas. When the human body moves within the detection range, it will enter the viewing area of the Fresnel lens in turn. It cannot be seen, so that the movement of the human body can generate continuously changing signals on the pyroelectric sensor in the form of temperature changes.

The third is to filter the impurity signals caused by white light, fluorescence, strong light, etc.

9. What is dual-detection detector? What are the common double detectors on the market?

In order to overcome the defects of a single-detection detector, detectors with different technical principles are usually integrated together. The dual-detection detector that only alarms when the sensors of the two detection technologies detect human body movement is called a dual-detection detector. Common dual-detection detectors on the market use microwave + passive infrared.

10. What is three-detection detector? What is four-detection Detector?

Three-detection detectors are just a gimmick promoted by some domestic manufacturers and sellers, using microprocessor technology as a detection method. In fact, this can only be counted as a three-detection detector. If all of these are considered as the three references, can the infrared microwave micro-processing anti-pet, anti-masking and anti-camouflage be called the six-detection detector? The real three-detection detector must have three detection technologies, such as: passive infrared + microwave + ultrasonic detector.

11. What is a vibration detector?

Vibration detectors are based on the vibration signals generated by detecting intruders carrying out various sabotage activities. For example, when intruders are carrying out sabotage activities such as cutting walls, drilling holes, destroying ATMs, and prying safes, these objects will be triggered. Vibration detectors that trigger alarms with these vibration signals are called vibration detectors.

12. What is the standard output signal of the detector?

The standard output signal of the detector is a switch signal, the common one is a normally closed detector, and the normally open or normally open/normally closed type can also be customized.

13. What is temperature compensation?

In general, human body temperature is always much higher than the ambient temperature. When the intruder moves, the detector receives a large change in the infrared signal and triggers an alarm. When the temperature of the nearby environment rises to be close to the temperature of the human body, the amplitude of the infrared change signal received by the detector when the intruder is moving is very small, so it is possible that the alarm will not be triggered because the signal is less than the trigger threshold.

Temperature compensation can automatically increase the gain of the intruder signal amplifier when the ambient temperature is close to the human body temperature, so that the signal of the external intruder can be captured and the sensitivity will not be affected by the ambient temperature.

14. Classification of detectors

According to the installation method of the detector, it can be divided into: wall-mounted, ceiling-mounted, and mounted

According to the detection range of the detector, it can be divided into: wide-angle type and curtain type