Which device integrates sequential logic to automate processes and is widely used in industrial control systems?

• A. GUI
• B. PLC
• C. Resistor
• D. Router

Answer: (B)

In automation, sequences are controlled by a device that reads sensors, makes decisions, and drives actuators in real time. That device is the Programmable Logic Controller. It runs a stored program that defines the steps of a process and how the system should respond to inputs, using sequential logic to move from one state to the next.

A PLC processes input signals from switches, sensors, and safety devices, decides what should happen next, and then updates outputs to control motors, valves, or conveyors. This setup supports timers, counters, interlocks, and state changes, so a machine can start, run through a sequence, and stop safely without human intervention. PLCs are built for harsh industrial environments and provide deterministic, repeatable behavior with a fast, regular scan cycle: read inputs, execute the logic, and update outputs.

In contrast, a graphical user interface is designed for humans to interact with software and monitor or control a system, not to autonomously implement a timed sequence of actions. A resistor is a passive electrical component that limits current; it does not control processes. A router manages networking traffic and data routing, not machine sequences or actuation.

So, the device that integrates sequential logic to automate processes and is widely used in industrial control systems is the Programmable Logic Controller.