8.1. On board communication equipment 1
Communication systems
Communication is essential for the effective operation of a ship both in regular and emergency situations. It is ensured by such systems as Public Address, Voyage Data Recorders, Marine Telephone Exchangers and sound-powered telephones for the internal communication on board.
A Public Address (PA) system is an electronic system for vessels and offshore port companies that includes a microphone, amplifier to strengthen the electrical signal, speakers, and related equipment to ensure the segregation of the announcements for separate spaces. It is used for command communication, shout out, General Alarm and entertainment. The system must be able to address emergency situations accurately, integrated with various other alarm systems, e.g. Fire Alarm, General Alarm, etc.
A PA system may include multiple microphones or other sources, a mixer to combine and change multiple sources, and multiple amplifiers and speakers for higher volume or wider distribution.
On board ships PA system is typically used for broadcasting messages into all spaces (engine room, crew cabins, muster stations) where crew members and passengers could hear the important announcements (about drills, warnings, weather conditions and so on) using the speakers. Hand-held loudspeakers could be used for crowd management during the emergency operations. The messages are usually broadcasted from the navigational bridge, but also it could be other places as administration deems necessary and only authorised personnel can use the system.
The PA on board a ship should withstand harsh conditions. Highest Ingress Protection (IP) ranges are to be used to protect it from the contamination by solids and liquids.
A Public Address system is very important to ensure the safety of facilities and people on board. It is designed to respond precisely to emergency situations through the connection with various alarm systems.
The Voyage data recorder (VDR) is a system assigned to record various data continuously. It can be used to reestablish details of a voyage during an investigation in case of an incident on board the vessel.
The VDR consists of Data Collecting Unit and Data Recording Unit. The DCU collects all data from sensors as IMO standards require. Also, it has a battery supply in case of ship power grid failure. Data from DCU is stored in DRU on a flash memory in a protective capsule, which keeps data for 48 or 72 hours.
The information stored on a VDR is data about ship’s position, movement, physical status, command and control of the ship, radio- and voice communication on the navigation bridge. This can help to analyse causes and consequences of an incident. The data records for the last 12 (or 48) hours and continues to be overwritten afterwards.
VDRs are capable of withstanding heavy weather, collisions, fires and pressure conditions, even when the vessel is underwater. It is located on the wheelhouse deck and can be attached to the hull with a hydrostatic link that breaks when underwater due to water pressure.
The VDR should provide looped records of data of the ship’s equipment and overall control of the vessel. The VDR system has established checks and maintenance routines to ensure its stable operation.