The present teaching relates to a magnetic sensor residing in a housing. The magnetic sensor includes an input port and an output port, both extending from the housing, wherein the input port is to be connected to an external alternating current (AC) power supply. The magnetic sensor also includes an electric circuit which comprises an output control circuit coupled with the output port and configured to be at least responsive to a magnetic induction signal and the external AC power supply to control the magnetic sensor to operate in a state in which a load current flows through the output port. The magnetic induction signal is indicative of at least one characteristic of an external magnetic field detected by the electrical circuit and the operating frequency of the magnetic sensor is positively proportional to the frequency of the external AC power supply.