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The Old System
Since 1899, when radio was first used at sea, it has helped to save
the lives of tens of thousands of people involved in maritime
disasters. The terrestrial radio telephony and telegraphy
system has proven itself reliable over many years, but the
system does have a number of serious drawbacks. They included:
- Quality of messages can be adversely affected by changes in propagation
conditions.
- Maximum range of the mandatory telegraphy and telephony equipment
is only about 250 km. A message transmitted in mid-ocean
is therefore unlikely to be received ashore.
- Morse telegraphy required many years of training and practice.
Apart from the radio operator, it was unlikely that anyone
else would be able to use the telegraphy equipment.
- Little chance of the frequencies allocated for maritime purposes
being increased as competition for frequencies became fierce
due to development of radio on land.
Advances
of technology led the IMO member governments to develop a new
system based on a satellite communications system devoted to
maritime purposes.
SOLAS Convention
GMDSS was introduced by means of amendments to SOLAS Convention
which were adopted in 1988 and entered into force on 1 February
1992 and became fully operational by 1 February 1999. On that
date, the 500 kHz Morse code system was phased out and all
passenger ships and all cargo ships of 300 gross tonnage and
above on international voyages would be required to carry
equipment to improve chances of rescue following an accident.
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