When the battery is completely depleted, how many LEDs blink per second?

• A. All LEDs off
• B. One LED blinking
• C. Three LEDs blinking
• D. Five LEDs blinking once per second

Answer: (D)

Indicator patterns communicate power state. When the battery reaches a critical/depleted level, the device uses a simple timing signal to drive all five LEDs in unison at a steady pace. Five LEDs blinking together at one cycle per second is easy to notice and clearly signals a warning while keeping energy use low. If only one LED blinked, the alert could be hard to detect; three LEDs blinking wouldn’t read as a single, unified warning; keeping all LEDs off would give no alert at all. So the five-LED pattern blinking once per second best conveys the depleted-battery condition.