What component in a PLC system receives external signals?

In a PLC (Programmable Logic Controller) system, the component responsible for receiving external signals is the input module. This module is essential because it interfaces with the various input devices, such as sensors, switches, and other types of field devices that generate signals based on physical phenomena. These signals are often in the form of voltage or current changes that reflect conditions like temperature, pressure, or position.

Once the input module receives these signals, it converts them into a format that the PLC can process, enabling the controller to execute appropriate control logic based on the received data. This integration of input data is crucial for the operation of automated systems, allowing for real-time monitoring and control of manufacturing processes and machinery.

The other components, while integral to the overall function of the PLC system, do not primarily handle the reception of external signals. Output modules send commands to actuators or output devices, communication modules facilitate data exchange between devices, and memory modules store the program and operating data.