Easily updated from weekly Admirality Notices for Mariners,
Coast Guard - A coast guard is a national organization responsible for various services at sea. However the term implies widely different responsibilities in different countries. In most countries is concerned with SAR (for example in the UK).
Space System for the Search of Vessels in Distress
Coast Radio Station - They are a maritime radio stations situated on shore which monitors radio distress frequencies, coordinate the radio traffic and relays ship-to-ship and ship-to-land communications. Some of CRSs are categorised as MRCCs or MRSCs or NAVTEX CRSs.
Digital Selective Calling - Broadcasting and receiving DSC Alerts is one of the major facilities on a VHF radio that is possible by VHF DSC controller. DSC alerts are used to “switch people on” to follow on with voice communication.
Duplex channels are normally only used for communication between vessels and CRS and for port operations and ship movement. With duplex channels our transmission can only be heard by the CRS. However, all ship stations listening to the same channel can hear the CRS transmission.
Emergency Position Indicating Radio Beacon - It is used as a distress alerting system, indicating to SAR authorities both the identity and position of a person or a vessel, which is in grave and imminent danger and requires immediate assistance.
Global Maritime Distress and Safety System - The GMDSS is an important part of the IMO (International Maritime Organisation) SOLAS (Safety Of Life At Sea) convention. It is an internationally agreed-upon set of safety procedures, types of equipment, and communication protocols used to increase safety and make it easier to rescue distressed ships.
Global Positioning System - Utilizing a constellation of at least 24 Medium Earth Orbit satellites that transmit precise microwave signals, the system enables a GPS receiver to determine its location, speed, direction, and time. GPS receivers may be found also on ships, for example as a part of navigational equipment and in some models of EPIRBs. They are usualy connected to DSC radio communication equipment, for example VHF radio.
Gross Register Tonnage - Represents the total internal volume of a vessel, with some exemptions for non-productive spaces such as crew quarters. 1 GRT is equal to a volume of 100 cubic feet (2.83 m³).