In LD programming, what term describes an output that remains ON until a secondary action turns it OFF?

In LD programming, what term describes an output that remains ON until a secondary action turns it OFF?

• A. Latch relay
• B. Normally Open
• C. Coil
• D. Resettable output

Answer: (A)

This describes a latching (self-holding) output in ladder logic. Once the activating condition energizes the coil, a holding contact closes and keeps the coil energized even after the input is removed, so the output stays ON until a separate reset action breaks the hold. A latch relay is specifically built to maintain its state until explicitly reset, making it the best term for this behavior. In contrast, a normally open contact only closes while energized and does not persist after the input drops, the coil energizes the device but doesn’t itself guarantee a maintained state, and resettable output isn’t a standard term for this mechanism.

This describes a latching (self-holding) output in ladder logic. Once the activating condition energizes the coil, a holding contact closes and keeps the coil energized even after the input is removed, so the output stays ON until a separate reset action breaks the hold. A latch relay is specifically built to maintain its state until explicitly reset, making it the best term for this behavior. In contrast, a normally open contact only closes while energized and does not persist after the input drops, the coil energizes the device but doesn’t itself guarantee a maintained state, and resettable output isn’t a standard term for this mechanism.