Annex 3 (cf. section 20)
General alarm and loudspeaker system
1. The general alarm system
1.1 The general emergency alarm system should be capable of sounding the general alarm signal consisting of seven or more short blasts followed by one long blast on the vessel's whistle or siren and additionally on an electrically operated bell or klaxon or other equivalent warning system, which should be powered from the vessel's main supply and the emergency source of electrical power. The system shall be capable of operation from the navigating bridge. The system shall be audible throughout all the accommodation and normal crew working spaces. The alarm shall continue to sound after it has been triggered until it is turned off manually.
1.2 The minimum sound pressure levels for the emergency alarm tone in interior and exterior spaces must be 80 dB(A) and at least 10 dB(A) above ambient noise levels existing during normal equipment operation with the vessel underway in moderate weather. In cabins without a loudspeaker installation, an electronic alarm transducer, e.g. an acoustic alarm (a buzzer) or similar, is to be installed, cf. section 20, sub-section 5.
1.3 The sound pressure level at the sleeping position in cabins and in cabin bathrooms is to be at least 75 dB (A) and at least 10 dB (A) above ambient noise levels.
2.1 Public address system
2.1 The public address system is to be a loudspeaker installation that makes it possible to broadcast messages to all spaces where crew members or passengers are normally found and to muster stations. The system shall make it possible to broadcast messages from the navigating bridge. The public address system must be installed with regard to acoustically marginal conditions and is not to require any action from the addressee. It must be protected against unauthorised usage.
2.2 With the ship underway in normal conditions, the minimum sound pressure level for broadcasting emergency announcements is to be:
2.2.1 in interior spaces 75 dB (A) and at least 20 dB (A) above the speech interference level, and
2.2.2 in exterior spaces 80 dB (A) and at least 15 dB (A) above the speech interference level.