What is the purpose of a memory (seal-in) element in ladder logic?

• A. To Keep An Output Energized After The Input Is Removed
• B. To Reset Outputs On Power-Up
• C. To Permanently Store Program Code
• D. To Gate Timing Functions

Answer: (A)

The memory (seal-in) element creates a latch that keeps an output energized even after its controlling input is released. It does this by using a contact that belongs to the same output to hold the circuit closed: once the output is energized, its own auxiliary contact closes and feeds current back into the rung, so the output remains on until something else interrupts it (like a stop input or a power cycle). This is the typical way to implement a “hold” function, such as starting a motor with a momentary pushbutton and then the motor staying on after you let go.

This isn’t about permanently storing code, resetting outputs on power-up, or gating timing functions. Those are different concepts: a memory element’s purpose is to maintain the state of an output through the latch mechanism, not to store code or control timing directly, and it will reset if power is removed or explicitly reset by another input.