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Old 17 October 2005, 07:34   #1
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DSC The Facts - An ICOM Guide

This article is available for download as a PDF from the ICOM web site

As you might expect it mentions specific ICOM radios -- the DSC functions are applicable to any DSC enabled VHF.

DSC is a marine distress calling system that will eventually affect a wide range of boat users. There are many misconceptions about it"s operation, both today and in the future. This booklet is designed to give as much information as possible about DSC, so that an informed decision can be made when purchasing new, or upgrading existing VHF/DSC equipment, now read on...

Background of Safety at Sea
For many years H.M. Coastguard has carried out a listening watch on VHF radio CH.16. They have provided a co-ordinated safety and information service to all maritime users around our coastline, ranging from large commercial vessels to small boat enthusiasts. Ever increasing levels of marine traffic coupled with the need to offer a modern, automated and coordinated service throughout Europe has meant that radical changes are needed.

GMDSS and all that
The SOLAS (Safety Of Life At Sea) International Convention laid down many measures designed to improve and maintain the safety of shipping. They apply to a wide range of commercial and passenger vessels.

GMDSS (Global Maritime Distress and Safety System) is an integral part of SOLAS. It is a radio-based communications system designed to support the implementation of search and rescue (SAR) plans.

The system provides automatic distress alerting and locating in cases where a radio operator doesn't have time to send a MAYDAY call. GMDSS will now, for the first time, broadcast maritime safety information that could prevent a distress from happening in the first place.

GMDSS consists of several systems, some of which are new, but many have already been in operation for a number of years.

The system will be able to reliably perform the following functions:
Alerting (includes position determination of the unit in distress);
Search and Rescue co-ordination; locating (homing);
Maritime safety information broadcasts;
General communications;
Bridge-to-bridge communications;
Specific radio carriage requirements depend upon the ship's area of operation, rather than its tonnage. The system should also provide backup means of distress alerting and an emergency source of power.

DSC - What is it?
DSC (Digital Selective Calling), as its name implies, uses digital data, rather than voice, to call other radios and transfer information between them. This mechanism provides several important benefits including increased volume and accuracy of data and the ability to direct the information to specific addressees (hence Selective Call).

DSC is primarily intended to initiate ship-to-ship, ship-to-shore, and shore-to-ship radiotelephone and MF/HF radio-telex calls.

DSC calls can also be made to individual ships or groups of ships. DSC distress alerts, which consist of a preformatted distress message, are used to initiate emergency communications with ships and rescue co-ordination centres. The effective range of communications when sending digital signals is also improved.

When fully implemented, DSC will eliminate the need for an individual on a ship's bridge, or shore station, to continually monitor radio receivers on voice radio channels. In particular VHF CH.16 (156.8MHz) and HF 2182kHz. The 2182kHz listening watch aboard GMDSS-equipped SOLAS ships has already ended on 1 February 1999. The VHF CH.16 watch will end in due course.

What is a DSC Controller?
A DSC controller is a unit that encodes and interprets DSC messages. The unit may be an external 'add-on' (as the DS- 100 shown here), but increasingly it is being offered built-in to VHF radios. DSC controllers have the ability to alert another vessel or rescue centre directly and exclusively and alert them to the fact that you want to talk, before opening voice communications on the normal VHF channels. In this respect, the system works rather like a pager with the recipient being alerted by an audio alarm, with different sounds for routine and distress calls.

Most importantly, before putting out an urgency safety message you can digitally alert "all ship". Or before broadcasting a Mayday, in the time-honoured way, you can transmit a distress alert at the press of a red button, which will set off an alarm in ship and shore stations within radio range.

What is an MMSI?
A Maritime Mobile Service Identity (MMSI) number is assigned to all vessels and is programmed into your DSC controller. This series of nine digits uniquely identifies a radio station (vessel) or group of radio stations (vessels). When sending a DSC message the MMSI is automatically included, and you can send messages to specific vessels or groups using their MMSI addresses. The MMSI has an internationally agreed format (just like a telephone number) and it identifies the type of station, country of registration and vessel identity. In the UK an MMSI is assigned as a part of a ship's radio licensing procedure.

GMDSS for the small boat user
Maritime organisations such as H.M. Coastguard, Maritime and Coastguard Agency (MCA), Royal Yachting Association (RYA) and the Royal National Lifeboat Institution (RNLI) are encouraging small craft which have voluntarily fitted VHF radio to fit VHF DSC.

Peter Dymond, Head of Search and Rescue at the Maritime & Coastguard Agency offers this advice. "H.M. Coastguard coordination centres monitor VHF CH.16 via loudspeaker only. The primary means of distress alerting in the VHF marine band should be via VHF/DSC. The monitoring of VHF CH.16 watch is likely to continue for the time being, as IMO has not endorsed any cessation of that commitment, in fact it has stated that ships at sea should continue to monitor VHF CH.16 when practicable".

He continues, "The policy for the remainder of maritime Europe is, as far as I am aware, much the same as the UK.We are committed to VHF/DSC both for routine and distress/urgency/ safety communications".

Stephen Johnson, RYA Cruising Manager strongly advises boat users, "When considering either buying or replacing your main VHF set, go for a DSC version". He added, "We do not wish to see a decision being made which stops the obligation on ships to monitor CH.16 in 2007. The RYA will lobby that monitoring continues, as they believe that there are not enough GMDSS units at the current time".

Rick Raeburn, Leisure Boat Safety Manager from the RNLI said, "The RNLI's position regarding DSC for leisure boaters is that there are definite safety advantages in having a DSC equipped radio and we have been encouraging boat owners to switch for some time".

John Finch from RT Training gives a Trainer's Perspective about VHF/DSC units. He says, "In my experience the majority of students attending a RYA Short Range Course (SRC) have already bought their VHF DSC equipment and they wish to learn how to use it, and to be legal. That's excellent, but I have always considered students would be better advised to attend the course prior to making the equipment purchase". Despite numerous articles about GMDSS in the Boating press many students initially have some misconceptions about the system and the equipment, for example:

DSC is just used in Distress.When you hit the red button - You are then rescued.
DSC makes voice communications obsolete - you text each other like a mobile phone.
DSC is unnecessary since the UK Coastguard is keeping the CH.16 listening watch.

During the SRC course the concept of the DSC system is explained, this soon dispels some of those popular misconceptions. In essence the system is designed to eliminate the need for shipping and shore stations to maintain a listening watch on CH.16. Instead equipment monitoring for data transmissions on CH.70 keeps watch. To make contact with another station, an alert (wake-up) data transmission is sent on CH.70 containing the voice channel on which you wish to communicate.

Undoubtedly, in Distress you do hit the Red Button and it does send out a comprehensive text message but subsequent communications are by voice on CH.16.

For non-distress traffic the data message is very basic and will only contain the sending stations Identity Number, the category of call, and the voice channel on which to communicate. So we can't use DSC to send a text message like the mobile phone, and it certainly hasn't made voice communications obsolete.

It is true the U.K. Coastguard have said they are going to maintain a CH.16 listening watch for the foreseeable future, but acknowledged that DSC was designed to eliminate the CH.16 listening watch. So in the near future don't expect other vessels to respond to your calls on CH.16. Also understand that outside U.K. waters, foreign Coastguards may not be listening on CH.16 but require you to call by DSC initially.

As SRC students gain an understanding of the system they realise DSC in not only for emergency use, but rather something they will use on a regular basis for routine contact with other vessels and shore stations. With this realisation they take a much more critical look at the DSC equipment itself.
They come to appreciate that small screens make reading the messages difficult, how background screen lighting is important and why small buttons make equipment operation difficult, especially on a moving boat. This conveniently returns me to my first point, which was. It's better to do the course before buying the equipment.

How will GMDSS actually affect me?
Yes. Large commercial ships may no longer keep a listening watch on CH.16, so they may not hear you calling on VHF unless you have a Digital Selective Calling (DSC) set. At the end of January 2005 the UK Coastguard will cease their dedicated headset watch on CH.16, although Coastguard stations will still monitor CH.16 on a loudspeaker in their operations rooms.

Peter Dymond, Head of Search and Rescue has this to say; "Due to the increasing range of communications methods available to the mariner and the other tasks now undertaken by Coastguard Rescue Co-ordination Centre staff, a different approach to managing an Operations Room is required. Neither the flexibility generated by operational partnerships between neighbouring co-ordination centres, nor an operator being continuously tied to a single task is of any help. However, our Operations Room Managers can still undertake a headset watch on VHF CH.16 if the risk, current operations, noise levels or other circumstances demand it".

He added, "Our state-of-the-art Integrated Coastguard Communications System (ICCS) also provides an instant playback facility for VHF CH.16 and the other VHF channels being monitored. Despite these changes, H.M. Coastguard will continue to be responsible for the integrity of VHF CH.16. This means ensuring that the channel is only used for distress, urgency and brief safety communications. This includes the announcement of maritime safety information broadcasts and the establishment of other communications which should be transferred to a suitable working channel".

Peter further added, "we also continue to recommend the installation of effective suitable equipment on vessels and would remind seafarers that mobile phones cannot be totally relied upon when at sea for distress and other emergency calls".

This is a change in emphasis and priority that all cruising sailors or motor cruisers should be aware of. Also, in the future other countries' coastguards may cease a CH.16 watch altogether. The date for this action is presently under review at the International Maritime Organisation (IMO), which is the maritime branch of the United Nations.

Do I need a licence?
You need a licence to operate a VHF/DSC radio. In the case of DSC radio, you need to ask for an MMSI number to be issued when you apply for the Ship Radio Licence. You also need to make sure that you have the appropriate authority to operate. For new users, this isn't a problem: sailing schools and local authorities all over the country offer one-day courses leading to the Short Range Certificate (SRC), which is all you need.

If you qualified for your licence before September 2000, you are most likely to have a VHF only licence. This is still valid, but only for non-DSC radios: if you use a radio with a DSC facility, you need to upgrade to a Short Range Certificate (SRC). In theory, you can do this by taking a direct-entry exam, or by taking half of the one-day SRC course, followed by the exam. In practice, most people in this situation take the whole course - because it usually costs the same and virtually guarantees that you'll pass.

What if I do not want DSC?
Just as there is no legal requirement for private leisure craft to have a VHF radio, there is no requirement that forces you to carry a DSC controller. Therefore you can fit an Icom IC-M503 VHF or even an IC-M401 VHF and carry on with voice-only VHF - saving yourself the complexity of DSC and the time of exchanging your old 'VHF only' licence to a new-style 'SRC'.

Distress calling with DSC
The big selling-point of DSC is the ability to make automatic distress calls. At little more than the touch of a button, you can alert ships and coastguards to the fact that you're in distress and simultaneously tell them what is wrong and where to find you. The standard procedure for generating that distress call is as follows:

1 Lift the protective cover over the panic button
2. Press and hold the panic button, usually between three and five seconds.
3. The radio will send a distress message
4. The display indicates that the distress message has been sent.Wait for an acknowledgement. If no acknowledgement is received, the radio will automatically repeat the call at intervals of about four minutes.

The Case for DSC
There is no question that GMDSS has a big part to play in improving safety at sea and it is here to stay.

Firstly a vessel's position and the time are automatically included in distress and urgency alerts if a DSC radio set is interfaced with a GPS navigator. If it is not, the position can be input manually. Secondly, a digital alert is more certain of reaching a maritime rescue centre than voice transmission, thanks to 15% greater range and not being prone to misunderstanding. Thirdly the increasing use of the digital broadcasting channel, CH.70, should make CH.16 more freely available for emergency use, while still being available for making contact.

Although there is no legal requirement for small boats to fit GMDSS equipment, you will still be indirectly affected by it.

Once DSC is fully implemented, any small boat in distress without some form of DSC equipment on board could find that there is no-one listening when they transmit on CH.16!

What should you buy?
There are 3 options:
Option 1. Carry on using your existing VHF radio for as long as it still works. You do not have to immediately buy a DSC set. The MCA and H.M. Coastguard are merely encouraging all pleasure craft voluntarily fitted with VHF to install VHF DSC. It is not a requirement to own a DSC set at this time. However, it should be noted that H.M.C.G. no longer maintains a dedicated headset watch of CH.16, although a loudspeaker watch is still kept. This is a move away from the original date of 2005.

Option 2. Buy a new VHF. If you sail inland in a RIB or just off shore and don't want the complication of a DSC, then a small-dedicated VHF like the IC-M401 would be ideal. If you have a powerboat or yacht and just want fixed VHF with dual-station control, then the IC-M503 and Commandmic should be on your shopping list. Both the IC-M503 and IC-M401 are DSC compatible so you could buy a DS-100 at a later date.

Option 3. Feel safe and prepare for the future and buy either the compact IC-M421 which is ideal for RIB's where space is at a premium. You could purchase the IC-M601, which is a larger unit giving dual-station control - the full DSC solution.

First time buyers are advised to choose Option 3. Icom UK hope that all the information in this booklet will prove useful and dispel some of the myths. If you have any further queries please contact our marine sales department or any of the addresses shown on the facing page - STAY SAFE AND HAPPY SAILING!
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