The infrared transmitter drives the infrared light emitting diodes to emit a noisy modulated infrared beam. At a distance from the infrared transmitter, an infrared receiver is placed in alignment with it. It receives the infrared radiation energy discovered by the transmitter through a phototransistor and converts it into an electrical signal through photoelectric conversion. This electrical signal is sent to the alarm controller circuit after appropriate processing.
The optical systems that are respectively placed at the receiving end and the emitting end are generally optical lenses, which function to focus the infrared light beam into relatively fine parallel light beams so that the infrared light energy can be transmitted in a concentrated manner. Infrared light is in the spectral range that is invisible to the human eye. Some people pass this invisible blockade line and must obstruct the infrared beam completely or partially. The intensity of the electrical signal output by the receiving end will change accordingly, thus starting the alarm controller to send an alarm signal. Infrared shooting alarm is characterized by very high detection reliability