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

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.

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.