If it is a three-wire ring proximity switch, the wiring method is as follows: the brown wire should be connected to the front port of the power supply, while the blue wire should be connected to the ov port of the power supply. The yellow line is the signal, which is to be connected to the load. The port of the load needs to connect the npn into the switch to the positive port of the power supply, while the pnp proximity switch needs to be connected to the ov terminal of the power supply.