5.4.1.1
Alarm Acknowledgement
A method of acknowledging all alarms (silence audible alarms
and set visual alarms to steady state), including the indication of
the source of the alarm, should be provided at the navigating and
manoeuvring workstation, to avoid distraction by alarms which require
attention but have no direct influence on the safe navigation of the
ship and which do not require immediate action to restore or maintain
the safe navigation of the ship.
5.4.1.2
Fire and Emergency
Alarms
The alarm indicators and controls of the fire alarm and emergency
alarm should be located at the safety workstation.
5.4.1.3
Failure or Reduction
of Power Supply
Alarms should be provided to indicate failure or reduction in
the power supply which would affect the safe operation of the equipment.
5.4.1.4
Sensor Input Failure
or Absence
Alarms should be provided to indicate sensor input failure or
absence.
5.4.1.5
Alarm Status
Alarm systems should clearly distinguish between alarm, acknowledged
alarm, and no alarm (normal condition).
5.4.1.6
Acknowledgement of
Alarms
Alarms should be maintained until they are acknowledged.
5.4.1.7
Cancellation of Alarms
Alarms and acknowledged alarm should only be capable of being
cancelled if the alarm condition is rectified. This cancellation should
only be possible at the individual equipment.
5.4.1.8
Alarm Minimization
The number of alarms should be minimized.
5.4.1.9
Alarm Testing
Provision should be made for functionally testing alarms.
5.4.1.10
Power supply
Required alarm systems should be continuously powered and should
have an automatic change-over to a stand-by power supply in case of
loss of normal power supply.
5.4.1.11
Indication of Alarms
Alarms should be indicated in order of sequence and provided
with aids for decision-making. An explanation or justification of
an alarm should be available (on request).
5.4.1.12
Presentation of Alarms
The presentation of alarms should be clear, distinctive, unambiguous,
and consistent.
5.4.1.13
Modes of Alarms
All required alarms should be presented through both visual
and auditory means.
5.4.2.1
Discrimination of Visual
Alarms
Visual alarms should clearly differ from routine information
on displays.
5.4.2.2
Presentation of Visual
Alarms
Visual alarms should be flashing. The flashing display should
change to steady display upon acknowledgement.
5.4.2.3
Presentation of Acknowledged
Alarms
Acknowledged alarms should be presented by steady display.
5.4.2.4
Presentation of Normal
Conditions (No Alarm)
Alarm indicators should be designed to show no light in normal
conditions (no alarm) or should be non-existent on displays.
5.4.2.5
Flash Rate
Flashing visual alarms should be illuminated for at least 50
% of the cycle and have a pulse frequency in the range of 0.5 Hz to
1.5 Hz.
5.4.2.6
Night Vision
Visual alarms on the navigating bridge should not interfere
with night vision.
5.4.3.1
Use of Audible Alarms
Audible alarms should be used simultaneously with visual alarms.
5.4.3.2
Audible Alarms
Audible alarms should go off upon acknowledgement.
5.4.3.3
Focusing on Audible
Alarms
Audible alarms should be differentiated from routine signals,
such as bells, buzzers, and normal operation noises.
5.4.3.4
Sound Characteristics
Under normal working conditions, the alarm signals should be
heard properly inside the wheelhouse and outside on the bridge wings
and their sound characteristics should not be inconvenient to the
human ear.
5.4.3.4.1
Sound Pressure
Audible alarm sound pressure, one metre from the source should
be at least 75 dB(A), and at least 10 dB(A), or preferable 20 dB(A),
above ambient noise levels existing during normal operations. Audible
alarm sound pressures in a space should not exceed 115 dB(A).
5.4.3.4.2
Sound Frequency
With the exception of bells, audible alarms should have a signal
frequency between 200 Hz and 2500 Hz, with the preferable range between
500 Hz and 1500 Hz.