External devices such as lamps, motor starters, and solenoids are examples of which PLC I/O category?

• A. Input devices
• B. Output devices
• C. Analog devices
• D. Digital devices

Answer: (B)

External devices like lamps, motor starters, and solenoids are outputs because they perform work in response to the PLC’s control signals. They sit on the PLC’s output side and receive a signal from the controller to take action—turning a lamp on, energizing a motor through a starter, or moving a solenoid. These devices are the actuated loads that the PLC controls, converting electrical energy into a physical effect. They’re typically digital outputs (on/off), though some systems use analog outputs for varying control. In contrast, input devices would feed data into the PLC from sensors, not provide action to the external world.