A specialized schematic that documents an industrial control logic system is called.

• A. Ladder diagram
• B. DC circuit diagram
• C. Fail safe design
• D. Reverse design

Answer: (A)

Ladder diagrams are a specialized schematic format used to document industrial control logic, especially for programmable logic controllers. They present logic in a way that resembles the old relay-based circuits: two vertical rails act as power lines, and horizontal rungs carry the logic elements like contacts (representing inputs) and coils (representing outputs). This layout makes it easy to visualize how energizing a set of inputs will turn on an output, breathe life into control sequences, and troubleshoot by tracing rung-by-rung paths. It’s the standard way engineers and technicians document control systems because it communicates the intended control behavior clearly and aligns with how control hardware is wired and tested.

Other options don’t fit this purpose. A DC circuit diagram shows general electrical connections for direct current, not specifically the control logic over a ladder-style representation. Fail-safe design is a design approach focused on safety and fault tolerance, not a schematic format. Reverse design isn’t a conventional term for documenting control logic.