What is the minimum duration of an intermittent audible trouble signal?

• A. 0.5 seconds
• B. 1 second
• C. 0.25 seconds
• D. 2 seconds

Answer: (A)

Intermittent audible trouble signals use short beeps to alert you to a fault without sounding like a full alarm. The beeps need to be long enough to be clearly heard in typical environments, so each pulse should be at least half a second. With a 0.5-second on-time (often followed by an equal off-time), you get a noticeable 1 Hz rhythm that signifies trouble distinctly from a continuous alarm. Shorter durations, like 0.25 seconds, can be easily missed in noise, while longer durations (1 or 2 seconds) risk blending into alarm signaling or becoming unnecessarily intrusive. So the minimum duration is 0.5 seconds.