Which element is used to keep an output energized after the input signal has been removed?

• A. Memory/Seal-In
• B. And
• C. Or
• D. Not

Answer: (A)

The ability to keep an output energized after the input is removed comes from a memory element called a seal-in (latch). When the input is true, the output energizes and its own auxiliary contact closes, creating a hold-in path that keeps the circuit closed even if the input goes away. This self-holding path maintains the output until something else breaks the circuit (like a stop input). In contrast, And, Or, and Not do not provide this memory capability: And requires both inputs to be present, Or only responds to inputs but won’t maintain state after inputs drop, and Not inverts a signal without holding the state.