What is DSC and Why You Should Have It

DSC or Digital Selective Calling is a paging system that enables DSC equipped marine radios to send a signal which is picked up by other DSC equipped radios that are in range. The DSC unit then alerts the radio operator, usually with audible and visual alarms. Once contact is established, communications are continued manually by voice on another channel.

The system was developed due to the large amount of marine radio traffic that is experienced in some parts of the world making emergency communications difficult.

Stations with a DSC enabled radio need a MMSI or Maritime Mobile Service Identity which is allocated by AMSA in Australia. This is programmed into the radio and identifies the calling station or ship. The system allows several levels of alert, the highest being distress which automatically alerts all stations in range. Other DSC calls can be sent to all stations or addressed to individual stations or groups using the MMSI.

VHF radio is the most common type of marine radio used by recreational boaters in Australia however there is no official shore based monitoring of VHF DSC. All commercial shipping and some volunteer rescue organisations now monitor DSC as well any recreational boats that have upgraded. In Australia VHF channel 70 is for DSC distress alerts only.

There are a number of advantages to using VHF DSC as a distress alert as opposed to solely relying on channel 16.

• If you only have time to press the DSC button your distress call has been sent
• The call will definitely alert any commercial vessels in range
• The digital signal sent by DSC has a greater range and is less affected by interference
• The MMSI identifies the boat in distress
• A GPS can be interfaced with the DSC radio so that the boats position is also transmitted
• The nature of the distress can be included in the alert

It seems obvious to me that we all should have one on our boats and every volunteer marine rescue organisation needs one. A new DSC VHF costs less than $400 and might just be the thing that saves you. Maybe the state governments could even supply them to the VMRs. This area falls under their responsibilities and they are always harping on about marine safety.

What do you think?