DSC Distress, Urgency, Safety and Routine Alerting – VHF CH 70 is exclusively available for DSC Distress, Urgency, Safety and Routine Alerts only. This channel must not be used for RT communications, so this is prevented by the communication equipment itself.
RT Distress, Urgency, Safety and Routine Calling – VHF CH 16 is exclusively available for RT Distress, Urgency, Safety and Routine Calling only.Public correspondence - CRS (Coast Radio Stations) – to interface between boats at sea with the main shore based telecommunications networks; provide facilities for testing VHF radios; transmitting weather forecasts, broadcasts and navigational warnings and coordinating SAR; coordinate Maritime or Medical Advice or Assistance; receive boat voyage reports on leaving or entering port and ETA (Estimated Time of Arrival), so on and so forth.
CG (Coast Guards) - may provide the same facilities as CRS with the exception of interfacing with main shore based telecommunications networks, in coastal regions where there are no CRS established.
Port Operations – provide radio communication services in harbour with port operators, pilot vessels, tugs, pilot stations and all associated VTMS (Vessel Traffic Management Services).
Inter-ship – used for radio communication between ships at sea.
On Board Communication – used for on board radio communications using handheld VHF.
Boat Marinas – provide availability of moorings, recommendations for sailing into port and harbour facilities and so forth. Irish marinas use VHF CH 80 channel. Dedicated VHF channels are available for particular geographical areas, for example CH M (157.850 MHz) and CH M2 (161.425 MHz) are “private” channels that have been allocated by the UK government specifically for use by marinas, yacht clubs and pleasure craft.
MSI (Maritime Safety Information) – this includes weather forecasts and broadcasts, navigational warnings and SAR information. Normally transmitted by RT to all stations by either shore based CRS or CG on working channels either at regular published times or indicated by initial alerting by DSC on VHF CH 70.
SAR (Search And Rescue) - used for search and rescue and anti-pollution operations. VHF CH 67 has been allocated in Ireland for the Coast Guard to communicate with its own assets (helicopters, rescue boats) during SAR incidents and training.