What component is used in a memory logic circuit?

• A. Control relay
• B. Input switch
• C. Output indicator
• D. Timer

Answer: (A)

Memory in logic circuits relies on a device that can hold a state even after the triggering input is removed. A control relay fits this role because energizing its coil can change its contacts to latch the circuit, keeping the state until a reset occurs. This ability to "remember" a condition is what makes a relay a common memory element in simple sensor logic systems. An input switch only affects the circuit while pressed, so it doesn’t store state. An output indicator merely shows the current state without memory. A timer introduces a delay but doesn’t maintain a remembered state once the trigger ends.