3 Principal characteristics

  3.1 The general emergency alarm system in all interior public accommodation spaces should have both a visual signal and an audible signal.

  3.2 The visual signal should be integrated into the general emergency alarm system such that activation of the general emergency alarm results in the concurrent activation of both audible and visual signals without further action.

  3.3 The device for producing the visual signal should have the same reliability and suitability for marine service as the other components of the general emergency alarm.

  3.4 The visual signal should not interfere with the ability of the crew to safely navigate the ship at night.

  3.5 The visual signal should be effective for alerting persons who are deaf or hard of hearing while minimizing the possibility of triggering seizures in passengers and crew who have photosensitive epilepsy. Visual signals with the following characteristics have been found to be acceptable^footnote:

• .1 the lamp should be a xenon strobe type or equivalent;

• .2 the colour should be clear or nominal white;

• .3 the effective intensity should not exceed 1,000 cd;

• .4 the flash rate should not exceed two flashes per second (2 Hz) nor be less than one flash every second (1 Hz) throughout the design voltage range of the device; and

• .5 the maximum pulse duration should be 0.2 s with a maximum duty cycle of 40%.

  3.6 To be effective, the visual signal device should comply with Table 1. This can be verified from a polar diagram of intensity and angles determined in accordance with an international or a national standard acceptable to the Administration.^footnote

  3.7 All visual signal devices within a field of view should be synchronized. This includes strobes operated by separate systems. The field of view includes viewing from an adjacent space. However, it is not necessary to synchronize visual signal devices and other strobes located in an adjacent main vertical zone (MVZ) due to a field of view extending through a doorway or other opening in the MVZ boundary, provided that the combined flash rate of all devices and strobes in such field of view does not exceed 4 Hz.

  3.8 For spaces equipped with the means of subdividing into smaller spaces (e.g. with movable bulkheads), the visual signal should be effective in each of the smaller spaces when so subdivided.

  3.9 The visual signal should be designed and installed in such a manner to be quickly noticed by an alert person anywhere within the space. Either of the approaches in 4.1 or 4.2 or an equivalent standard acceptable to the Administration is suitable.