Which PLC component connects directly to field devices such as pilot lights, motor starters, and solenoids?

• A. Input module
• B. Output module
• C. CPU
• D. Power supply

Answer: (B)

Connecting field devices to a PLC is done through the outputs. The output module is the interface to actuators and indicators like pilot lights, motor starters, and solenoids. The CPU runs the program and sends on/off signals to the output channels, and the output module supplies the actual voltage and current to energize the devices. Output modules can be relay-type or transistor-type, chosen to match the device requirements. This role is different from the input module, which reads signals from sensors, and from the power supply and CPU, which provide power and perform processing. So the component that connects directly to field devices is the output module.