Section 4 Systems

4.1.1 Alarms associated with navigation equipment are to be both audible and visual and are to be centralised for efficient identification. Repeater displays may be fitted on the bridge wings and at other appropriate positions on the bridge where necessary.

4.1.2 The following alarms are to be provided:

• Closest point of approach.
• Shallow depth.
• Waypoint approaching (where automatic track following is provided).
• Off-course.
• Off-track (where automatic track following is provided).
• Steering alarms, see Table 19.5.1 Alarms in Pt 5, Ch 19 Steering Systems or Table 20.4.1 Alarms for control systems in Pt 5, Ch 20 Azimuth Thrusters, as applicable.
• Navigation light failure alarms, see Pt 6, Ch 2, 15.6 Navigation lights, including Pt 6, Ch 2, 15.6 Navigation lights 15.6.8 for grouping.
• Gyrocompass failure.
• Watch safety system failure.
• Failure of any power supply to the distribution panels referred to in Pt 7, Ch 9, 4.4 Power supplies 4.4.1.

4.1.3 Audible signals are to be designed not to startle operators. Suitable types are shown in Table 9.4.1 Suitable audible signals.

4.1.4 In the event that any alarm initiated by navigation equipment on the navigating bridge has not been acknowledged on the bridge within a period of 30 seconds, a visual and audible alarm is to be initiated immediately to warn the appointed back-up navigator and/or the Master.

4.1.5 In the event that the alarm required by Pt 7, Ch 9, 4.1 Alarm and warning systems 4.1.4 is not acknowledged, the system is to initiate an alarm at the locations of further crew members capable of taking corrective actions following a time delay sufficient to allow the Master or back-up navigator to reach the bridge. The time interval is to be adjustable between 90 seconds up to a maximum of 3 minutes. In ships, other than passenger ships, the alarm to warn the further crew members may be initiated at the same time as the alarm to warn the Master and back-up navigator.

4.1.6 The functionality specified in Pt 7, Ch 9, 4.1 Alarm and warning systems 4.1.4 and Pt 7, Ch 9, 4.1 Alarm and warning systems 4.1.5 may be incorporated in the watch safety system required by Pt 7, Ch 9, 4.2 Watch safety system, or in another fixed system.

4.2.1 A watch safety system satisfying the requirements of the IMO Resolution MSC.128(75) - Performance Standards for a Bridge Navigational Watch Alarm System (BNWAS) - (adopted on 20 May 2002) and approved by the national administration is to be provided to monitor the well-being and awareness of the watchkeeper.

4.2.2 If, depending upon the shipboard work organisation, the backup navigator may attend locations not connected to the alarm transfer system, a wireless portable device is to be provided enabling both the transfer of alarms and two-way speech communication with the bridge. An audible warning from the portable device is to be provided in the event of loss of the wireless link with the bridge. Alternative arrangements will be considered.

4.2.3 Acknowledgement of any alarm is to automatically reset the time interval between warnings. Manual adjustment of controls may also be used for this purpose. Manual adjustment of controls and navigation equipment (see also Pt 7, Ch 9, 5.3 Equipment 5.3.14) is to automatically reset the watch safety interval timer. Reset arrangements based on the detection of movement in the bridge are not considered to satisfy this requirement or to confirm well-being and watch-keeping awareness.

4.3.1 A telephone system is to be provided to enable two-way speech communication between the wheelhouse and at least the following locations:

• machinery control station space, see Pt 6, Ch 1, 2.6 Bridge control for main propulsion machinery 2.6.7;
• emergency steering position in the steering gear compartment;
• Master's and Navigating Officers' cabins, offices, mess and public rooms.

4.3.2 The bridge is to have priority over the system.

4.3.3 A list of extension numbers is to be clearly displayed adjacent to each telephone.

4.4.1 Local distribution panels are to be provided for all items of electrically operated navigational equipment, the telephone system, the watch safety system and the clear view systems. These panels are to be supplied by two exclusive circuits, one fed from the main source of electrical power and one fed from an emergency source of electrical power. Each item of equipment is to be individually connected to its distribution panel. The power supplies to the distribution panels are to be arranged with automatic changeover facilities between the two sources, see also Pt 6, Ch 2, 15.7 Navigational aids. Failure of any power supply to the distribution panels is to initiate an audible and visual alarm. This alarm should be included in the ship's alarm system, as required by Pt 6, Ch 1, 4.2 Alarm system for machinery, where applicable.

4.4.2 The watch safety system and the telephone system are to remain operational during blackout conditions.

4.4.3 Following a loss of power which has lasted for 45 seconds or less, all navigation functions are to be readily re-instated. In this respect, all navigational equipment is to recover within five minutes, with minimum operator intervention, by virtue of the emergency source and, where necessary, an uninterruptible power source.