The principle of the acousto-magnetic system: The transmitter of the detection system emits 58kHz low-frequency magnetic waves intermittently at 1/75 second, forming a detection area around it.
When a tag composed of two special amorphous metal sheets enters the detection area, due to interference to the electromagnetic field or other forms of induction, that is, a resonance signal, this signal will be received by the supporting receiver, causing the system to alarm.