Regal 3300 Owner's Manual page 40

CHAPTER 1
The electric distress flag is for night use only flashing the international
SOS distress signal (..._ _ _ ...).
Under Inland Navigation Rules, a high intensity white light that flashes
at regular intervals from 50-70 times per minute is considered a distress
signal.
Remember that regulations prohibit the display of visual distress signals
on the water under any circumstances except when assistance is required
to prevent immediate or potential danger to passengers on a vessel.
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