Ian Waugh - A Mariner\'s Guide to Marine Communications

Distress, Urgency and Safety communications should normally be
conducted exclusively on GMDSS radio/satellite communications
equipment. Non-GMDSS equipment should only be considered if
GMDSS equipment has failed to gain the assistance required
(Distress/Urgency), or to pass a safety message.
OTHER
All communications which are not classed as Distress, Urgency or
Safety are, in the GMDSS, classed as Other communications and will
include (i) normal communications with ports, pilots and ship movement!
vessel traffic services; (ii) normal intership communications and (iii)
private/business calls/messages in the 'public correspondence' service
(i.e. normal ship-shore telephone, fax and data calls and telex/e-mail
messages).
'Other' communications with ports, pilots and ship movement/vessel
traffic services will normally be carried out using GMDSS radio
equipment. Intership communications will normally be conducted on
GMDSS radio equipment. Communication in the public
correspondence service may be carried out on GMDSS radio or
satellite communications equipment - but is increasingly being carried
out on non-GMDSS/non-marine radio and satellite communications
equipment (including Cellular Radio and non-GMDSS Mobile
Satellite Services like Inmarsat-M and Inmarsat-Mini-M - both
covered in Chapter 4).

G MDSS functions

The GMDSS was progressively introduced between 1992 and

February 1999. It introduced two fundamental changes from the pre-

GMDSS system for distress and safety communications:

(i) the traditional aural (listening-by-ear) watch, carried out by radio

operators ashore and afloat, was replaced by automatic alerting

systems. This particularly applies to distress watch keeping and to the

reception of maritime safety information; and

(ii) a list of GMDSS functions was introduced - requiring ships to be

able to :

• send 'Distress Alerts' from ship-to-shore; receive 'Distress Alerts'
  from shore; and send/receive ship-to-ship Distress Alerts. In the
  GMDSS, the first priority for ships in distress is (normally) to get
  a Distress Alert!Message to a shore-based Rescue Coordination
  Centre (RCC) so that, if that was the only opportunity to
  MARINE COMMUNICATIONS 3