CNC machine tools PLC consists of two types of interface information, namely electrical interfaces of the hardware information and register the software interface information.
1. the signal flow including input and output interfaces
2.From the signal amplitude characteristics including analog and switch interfaces
Input signal: composed of machine transfer signals to the PLC or CNC external device known as the input signal.
Output signal: from PLC to machine or CNC external devices such as transmitting signals known as output signal.
PLC common electrical interface switching input interface, switch outputs and analogue output interface 3.