What the hell is DSC anyway?

What the hell is DSC anyway?
1/05/12 1:42 PM
DSC is probably the least understood yet widely available safety tool in marine electronics . The term DSC is an acronym of“Digital Selective Calling” and can apply to both SSB or VHF radios. To make matters more confusing, VHF DSC is split into 2 classes, Type A is for offshore ships and requires a bit more hardware, while type D is for regular boaties, which is what we are interested in. DSC can be used for a wide variety of things, however the most important job is that of the distress button, which is normally located under a little plastic flap. So what exactly happens when you push this little red button? We decided to find out.
Our test radio was a Nautilus Lifeline– a diving VHF which has an integrated GPS and DSC function. Its an amazing little package and is waterproof to 120m! It was set up with an MMSI number which is an essential step if you want to use your DSC radio for emergency purposes. MMSI numbers are issued when requested with VHF callsigns, which you should have by law. For more information see this page. For receiving we used a standard, unregistered Uniden UM380 radio, which was located inside our showroom and did not have a GPS input.
When the emergency button was pushed, the DSC radio in the shop started to make an alarming sound, and switched itself to channel 16. The noise was quite impressive coming out of the UM380 until we shut it up by pushing the cancel button. The coordinates of the distress radio were shown on the screen, as well as a flashing “distress”. The important part of this is the other radios changing to channel 16. Any mayday call then made will be recieved by a larger group of boaties.
Probably the most interesting part of our test was the reaction from other users. Firstly no authorities monitor VHF DSC (Maritime Radio do officially monitor SSB DSC). I also checked with the Coastguard after the test, and they confirmed they had not received any alarms at their station. This isn't a major however as Maritime Radio keep a constant watch on 16, and you should also put out a mayday anyway. The second user I had contact with was a commercial fisherman who asked me to get rid of the flashing message symbol on his VHF radio a couple of days later. This turned out to be the emergency messages from our test. To him, the alarms were no more than an annoying noise coming from the bridge.
So, is DSC worth the hastle of getting an MMSI number and the cost of a GPS input? Given that about half of the radios we sell have DSC I would say, yes it is. The button function by itself is not going to do you any good, and Maritime Radio does not officially monitor this, however it does is change DSC radios within range to channel 16, so any subsequent mayday calls will be received by a larger number of boaties, which is always a good thing when you're in trouble. However it is not a silver bullet, and should not be used without putting out some other source of mayday or distress call.

this info is forwarded on from http://baymarineelectronics.co.nz/latest_news/dsc/