46 C.F.R. § 161.013-9 Independent power source.
Title 46 - Shipping
(a) Each independent power source must be capable of powering the light so that it meets the requirements of §161.013–3(a)(1) and emits a recognizable flash characteristic of the International Morse Code for S-O-S at a rate of between 3 and 5 times per minute after six hours of continuous display of the signal. (b) If the independent power source is rechargeable, it must have a waterproof recharger designed for marine use. (c) If the independent power source requires external water to form an electrolyte, it must operate in sea water and fresh water.
Title 46: Shipping
PART 161—ELECTRICAL EQUIPMENT
Subpart 161.013—Electric Distress Light for Boats
§ 161.013-9 Independent power source.
