Answer / cae

Plc basically contains Inputs and outputs along with CPU. programme written in ladder logic or in any other language like FBD,ST,IL it is stored in PLC memory which deals with CPU. Field sensors are connected to the input card of plc as a reference signal or getting feedback from the field by sensors. so according to the logic plc sends a signal to the output card which correspondingly enables the Electrical output,it may be a motor contactor coil or drive through a relay for safe operation and plc sends the output signal with very low voltage level enough to enrgize the relay coil or contactor coil or an SSR(solid state relay) This is the way how plc gives commands to electrical. and ***Communication plays a vital role for plc operation

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