DSC
Digital Selective Calling (DSC)DSC is a semi-automated method of establishing a radio call, it has been designated by the International Maritime Organization (IMO) as an international standard for establishing VHF, MF and HF radio calls. It had also been designated as part of the Global Maritime Distress and Safety System (GMDSS). It is planned that DSC will eventually replace aural watches on distress frequencies and will be used to announce routine and urgent maritime safety information broadcasts.This new system will allow mariners to instantly send a distress call with GPS position (when connected to the transceiver) to the US Coast Guard and other vessels within range of the transmission. DSC will also allow mariners to initiate or receive distress, Urgency, Safety routine, POS Request, POS Send and Group calls to or from another vessel equipped with a DSC transceiver.USCG DSC WatchThe USCG has plans to upgrade its VHF National Distress System (expected by 2005), so at this time (March ‘04) only larger vessels that are required to carry VHF DSC radios, other boater with VHF DSC radios and most towing companies will be able to hear your distress transmissionMaritime Mobile Service Identity (MMSI)An MMSI is a nine digit number used on Marine Transceiver capable of using Digital Selective Calling (DSC). This number is used like a telephone number to selectively call other vessels.How can I obtain an MMSI assignment? Boat US is offering MMSI free MMSI numbers. Visit the following to register: http://www.boatus.com/mmsi/.Distress CallTransmits a DSC Distress message to all radios equipped to receive a DSC Distress call. Some VHF radios may be connected to a GPS to also transmit the Latitude, Longitude of the vessel.Individual CallThis feature allows the user to contact another vessel capable of using DSC and automatically switch the radio to a desired working channel. This feature is similar to calling a desired vessel on CH16 and requesting them to go to another channel.Urgency CallThis call should be used when a vessel may not be truly in distress, but have a potential problem that might lead to a distress situation.Safety CallUsed to transmit boating safety information to other vessels. This message usually contains information about an overdue boat, a derelict afloat, loss of a navigation aid or an important meteorological message.POSITION REQUESTAdvancements in DSC have made it possible to poll the location of another vessel and show the position of that vessel on the display some VHF's. Some VHF’s have taken this feature one step further (ie: if any Standard Horizon GPS is connected a Standard Horizon VHF with this function the polled position of the vessel is shown on the display of the GPS chart plotter making it easy to navigate to the location of the polled vessel). This is a great feature for anyone wanting to know the position of anther vessel for example you buddy that is catching fish, or finding the location of a person you are cruising with.POSITION SENDThe feature is similar to Position Request, however instead of requesting a position of another vessel this function allows you to send you position to another vessel. Your vessel must have an operating GPS receiver connected the a Compatible VHF to send the position.When other vessel receives your position, the transceiver outputs the position to the GPS chart plotter to show your position on the receiving transceiver.CALL WAITING DIRECTORYThe DSC Call Waiting directory logs received distress individual calls that are received and not answered within 5 minutes or while the radio is set on the DSC Standby function. Calls will be logged while busy with other communications as long as the transmitter is not keyed at the time of the call. If the call is answered within 5 minutes the call will not be logged. When a call is logged, a message will appear on the LCD. ADDITIONAL DIGITAL SELECTIVE CALLING INFORMATIONFor additional information the USCG has an excellent site that should be visited at www.navcen.uscg.mil/marcoms/gmdss/dsc.html.