46 C.F.R. § 27.201
(a) You must ensure that your vessel is fitted with a general alarm that:
(3) Has installed, in the engine room and any other area where background noise makes a general alarm hard to hear, a supplemental flashing red light that is identified with a sign that reads:
Attention General Alarm—When Alarm Sounds or Flashes Go to Your Station.
(b) You or the operator may use a public-address (PA) system or other means of alerting all persons on your towing vessel instead of a general alarm, if the system—