What exactly does the output mode (PNP NO&NPN NC) of the proximity switch refer to? How to connect with PLC?

PNP NO: the switch is triggered, the output is valid when the high level, the voltage is close to the positive terminal voltage of the power supply, NO means "switch contact" is normally open (Normal Open), that is to say, usually the switch is disconnected (voltage 0), triggered to turn on (voltage = VCC).PLC inputs need to be **** low input, that is, the input terminal of the public **** end and GND connection. connection.

NPN NC: the switch is triggered, the output is valid when the low level, its voltage is close to the negative side of the power supply voltage 0, NO means "switch contact" is normally closed (Normal Close), that is to say, usually the switch is closed (voltage = VCC), triggered by the switch on (voltage = 0).PLC inputs need to be *** high inputs, that is, the male*** of the input terminals are connected to VCC. ** terminal is connected to VCC.