Which description best describes an E-stop button in safety systems?

• A. Momentary pushbutton
• B. Maintained latch pushbutton
• C. Lock-off (détente) self-latching mushroom operator type
• D. Pushbutton with LED indicator

Answer: (C)

An E-stop is meant to instantly and reliably stop machinery and keep it stopped until a deliberate reset action is taken. The best description is a self-latching, lock-off mushroom-style pushbutton with a detent. The mushroom head makes it quick to find and press in an emergency, while the self-latching mechanism ensures the stop position remains engaged even after the operator releases the button. The detent provides a tactile cue and a physical lock, so the stop state stays in place until the reset is performed. This combination prevents accidental re-starts and ensures a clear, safe reset process.

A momentary pushbutton would release as soon as you let go, failing to guarantee a safe off. A plain maintained latch pushbutton might not include the explicit self-latching and detent features specific to a true E-stop. A pushbutton with an LED indicator shows status but does not by itself guarantee the stop condition or the proper reset behavior.