How does a mechanical interlock prevent two incompatible operations from occurring in sequence?

• A. It physically prevents engagement of one device when the other is active, maintaining safe operating order.
• B. It uses electronic logic to sequence operations.
• C. It senses overload and stops both devices.
• D. It delays one operation with a timer.

Answer: (A)

A mechanical interlock works by a physical linkage that makes one device block the other from moving when it is engaged. When you operate the first device, a part such as a latch, pawl, or interlock bar moves into a position that physically prevents the second device from closing or starting. Because the blockage is mechanical, the two devices cannot enter conflicting states at the same time, so the system remains in a safe, sequential order.

This is different from electronic logic-based interlocks, which use circuits to enforce sequencing, or from timer-based delays, which rely on time to control order. It also isn’t about protecting against overloads, which is what protection devices do. The essence of a mechanical interlock is the direct, physical prevention of the second operation to keep incompatible actions from occurring in sequence.