Why does the stereo click when the mobile phone sends a text message?

Electromagnetic interference (EMI) includes conducted interference and radiated interference. Conducted interference refers to the coupling (interference) of signals on one electrical network to another electrical network through conductive media. Radiation interference refers to the interference source coupling (interfering) its signal to another electrical network through space. In the design of high-speed PCB and system, high-frequency signal lines, pins of integrated circuits, various connectors, etc. It may become a radiation interference source with antenna characteristics and can emit electromagnetic waves, which will affect the normal work of other systems or other subsystems in this system.

Electromagnetic interference (EMI) EMI is electronic noise that interferes with cable signals and reduces signal integrity. EMI is usually generated by electromagnetic radiation sources such as motors and machines.

Since the mid-1970s, the noise reduction technology of electronic system appeared, mainly because the Federal Communications Commission of the United States put forward the relevant regulations on commercial digital products in 1990 and the European Union in 1992. These regulations require companies to ensure that their products meet strict magnetization coefficient and emission standards. Products that meet these requirements are called electromagnetic compatibility (EMC).

Supplement: answering the phone or sending messages by mobile phone is the transmission and sending of radio signals. Electricity produces magnetism. Why does the stereo sound when it is connected to the power supply? Because the changing current vibrates the sound film in the sound, since they are the same two electromagnetic signals, they will inevitably interfere with each other.

You can try. When you turn off the audio power, there will be no such interference.

You can easily find out the specific principle of vocalization, that is, the change of current produces different vibrations to vocalize.