Authority Identification Code
Admiralty Digital Radio Signals.
AIS Search and Rescue Transmitter.
Admiralty List of Radio Signals.
Amplitude Modulation. A form of modulation where the amplitude of a carrier wave is made to vary in sympathy with the amplitude of the input signal. It is also known as A3E, when used for analogue voice double
The short–form term for ampere. A measurement of electrical current in a circuit, commonly called an ‘amp’. One ampere is a certain number of electrons passing by the point of measurement in one second. Symbol for ampere(s) is A.
Australian Maritime Safety Authority.
Automated Mutual–Assistance Vessel Rescue System. AMVER is a computer–based voluntary global ship reporting system used worldwide by search and rescue authorities to arrange assistance to persons in distress at sea. It is sponsored by the United States Coast Guard.
A string of telex characters which uniquely identify an individual telex machine or terminal. It can be sent from a telex terminal via the ‘HERE IS’ command, and requested from another telex machine via the ‘WRU?’ (Who are you?) command.
Automatic Retransmission Request. A NBDP (telex) technique for detecting and correcting transmitted errors, requiring an automatic transmitted response from the receiving station. Communications are limited to a single transmitting and a single receiving station.
American Standard Code for Information Interchange. A popular code for the exchange of information between computers, computer terminals and other data applications.
Aid To Navigation.
Built–in Integrity Test. Used in AIS equipment.
Binary Digit. One of the digits 0 or 1 used in binary notation. It is the basic unit of information in computers, data processing or digital communications.
Built–in Test Equipment. Used in radio and other electronic equipment.
A group of bits taken together and treated as a unit in computers, data processing or digital communications. Typically one byte consists of 8, 16, 32, 64 or 128 bits, depending on the technology.
A land station in the maritime mobile service providing terrestrial communications to and from ships at sea.
General call to all stations. Frequently used in Morse transmissions, and sometimes in voice communications.
‘from.’ Used to precede the name or identification of the calling station. Frequently used in Morse and telex transmissions.
Digital Selective Calling (DSC)
A system in the GMDSS for transmitting distress alerts from ships and for transmitting associated acknowledgements from shore stations. It is also used for relaying distress alerts and for alerts prior to the broadcast of urgency and safety messages.
The DSC transmission of a distress alert indicates that a mobile unit (ship, aircraft or other vehicle) or person is threatened by grave and imminent danger and requests immediate assistance. It is sent using a DSC format in the bands used for terrestrial radiocommunications or a distress message format, in which case it is relayed through space stations. It is normally followed by a distress call on the associated R/T channel. The distress alert shall provide the identification of the station in distress and its position.
Data Network Identifier. A digital ID downloaded to a ship’s Inmarsat–C terminal, to permit Automated Position Reporting (i.e. to allow polling of the ship’s position).
Disaster Recovery Facility. (ie. AMSA backup facility)
Operating method in which transmission is possible simultaneously in both directions of a telecommunication channel.
Electronic Chart Display and Information System. A computer–based navigation information system that complies with IMO regulations.
Extra High Frequency. (30 to 300 GHz)
Enhanced Group Calling (EGC)
Emergency Position Indicating Radio Beacon.
A frequency–modulated mode of emission using digital information for automatic reception, without the use of a modulating sub–carrier.
A frequency–modulated mode of emission using analogue telephony (i.e. voice).
Forward Error Correction. An error–tolerant broadcast mode for NBDP, where the sending station transmits to an unlimited number of receiving stations.
Provides global voice, fax and high–speed data communications at speeds up to 128 kb/s via Inmarsat. It is suitable for a wide range of vessels, from deep–sea ships to offshore support craft. Provides full support for GMDSS, including features such as emergency call prioritization, as stipulated by IMO Resolution A.888 (21).
The international commercial service offered under Inmarsat–C’s EGC capability, which allows authorised information providers, such as commercial subscription services, shipping companies or governments to broadcast messages to selected groups of vessels, each of which has registered with the information provider, and been added to a FleetNET closed group / network.
Frequency Modulation. The frequency of a carrier wave is made to vary in sympathy with the frequency of the input signal. Used for VHF marine band transmissions
A Local User Terminal in the Cospas– Sarsat system for receiving signals from geostationary satellites fitted with Cospas–Sarsat packages. See also LUT.
A satellite whose period of revolution is equal to the period of rotation of the earth and whose circular and direct orbit lies in the plane of the Earth’s equator; that is, a satellite which remains in the same relative position to any point on Earth. Approximate altitude of satellite is 36 000 km above earth’s surface.
Gigahertz (1 000 000 000 hertz). A measurement unit of radio frequency, oscillation and vibration equaling 1 000 000 000 cycles per second.
Global Maritime Distress and Safety System.
Greenwich Mean Time (see also UTC).
Global Navigation Satellite System (eg. GPS,Glonass, Galileo).
General Operator’s Certificate of Proficiency
Global Positioning System. A satellite
Gross Tonnage (replaces Gross Registered Tonnage (GRT))
Radiotelephony using amplitude modulation, single sideband, full carrier
High Frequency (3 to 30 MHz)
Locating signals transmitted by a ship in distress or survival craft to provide a bearing for searching vessels and aircraft.
International Civil Aviation Organisation.
International Maritime Dangerous Goods Code.
International Maritime Organisation.
International Mobile Satellite Organisation.
Inmarsat Ltd (formerly International Maritime Satellite Organisation)
International Code of Signals
Integrated Services Digital Network. A digital access network for data and voice, which provides an alternative to the public switched telephone network.
International Safety Management. Refers to the IMO’s International Safety Management (ISM) Code 2002, which provides an international standard for the safe management and operation of ships, and for pollution prevention.
International Telecommunication Union. The lead United Nations agency for information and communication technologies.
ITU Radiocommunication Sector (ITU—R) is that part
of the ITU which performs
a major role in the global
management of the radio—frequency
spectrum and satellite orbits, for services such as fixed, mobile,
space research, emergency telecommunications, meteorology, global positioning systems, environmental monitoring and
communication services, that ensure safety of life on land, at sea and in the air. Formerly known as the CCIR.
Radiotelephony using amplitude modulation, single sideband, suppressed carrier. Often referred to as ‘SSB’.
Japanese Ship Reporting System
Australian Joint Rescue Coordination Centre, located in Canberra.
Kilobits per second. One kilobit equals 1 000 bits.
Kilohertz (1 000 hertz). A measurement unit of radio frequency, oscillations and vibrations equaling 1 000 cycles per second
Kilometre. (1 000 metres)
Knot. One nautical mile per hour.
Land Earth Station (LES)
An earth station in the maritime mobile
Low Earth Orbit Local User Terminal. As used in the Cospas–Sarsat system. See also LUT.
see Land Earth Station
Low Frequency (3 to 30 kHz)
Local Sea Safety Messages. Contain warnings which refer to hazards which are considered to be of a temporary nature, eg. floating logs, temporary buoys, etc, broadcast for a defined period.
Local User Terminal (LUT)
A ground receiving station which receives data from COSPAS and SARSAT satellites, calculates the position of the beacon and forwards the resultant information to rescue authorities.
Transmissions intended to facilitate the location of ship in distress or survival craft.
Long Range Identification and Tracking. A ship reporting system requiring ships to automatically transmit their identity, position and date/time at 6–hour intervals, as part of Maritime Domain Awareness, by contracting Governments under SOLAS.
Lower Sideband mode of emission. A form of single sideband emission, where only the lower sideband is transmitted.
Metre. Unit of length.
Maritime Safety Information (MSI)
Distress Alerts, navigational warnings, meteorological warnings and forecasts and other important safety information for ships.
Modernised Australian Ship Tracking and Reporting System (replaces AUSREP).
Maritime Communications Station. Another term for a coast station.
Medium Frequency (300 to 3 000 kHz).
Medical and First Aid Guide. Part of the International Maritime Dangerous Goods Code.
Megahertz (1 000 000 hertz). A measurement unit of radio frequency, oscillation and vibration, equaling 1 000 000 cycles per second.
Minimum Keyboard and Display. A minimal text only display provided for AIS Class–A transceivers.
Mobile Packet Data Service. An Inmarsat service allowing continuous connection of ships to terrestrial networks with payment for volume of data exchanged, rather than the duration of ‘airtime’ used.
Marine Radio Operator’s Certificate of Proficiency. Replaced by Long Range Operator Certificate of proficiency.
Maritime Safety Committee of the IMO.
Maritime Safety Information. Navigational and meteorological warnings, meteorological forecasts and other urgent safety related messages.
Maximum Usable Frequency. The highest frequency which is reflected by the ionosphere over any particular path.
A Navigation Area in the world
Navigational warning broadcast issued by an area coordinator of the world
Narrow Band Direct Printing. Formerly known as ‘telex over radio’.
Network Coordination Station in the Inmarsat system.
Navigation, Communication and Search and Rescue. An IMO sub-committee.
Communications between the distressed ship or survival craft and assisting units.
Public Switched Telephone Network.
Press to Talk. A switch used on microphones and control lines, to activate the voice path and activate transmitter circuitry.
Radiotelephony (i.e. voice).
Rescue Coordination Centre.
A mandatory Ship Reporting System for the Great Barrier Reef and Torres Strait. Otherwise known as the Great Barrier Reef and Torres Strait Ship Reporting System.
Rescue Coordination Centre (RCC)
A unit responsible for the efficient organisation of search and rescue services and the operation of these resources within a nominated area.
Receiver or receive frequency
Search and Rescue.
SAR coordinating communications
Communications necessary for the coordination of ships and aircraft participating in a search and rescue operation.
Super High Frequency (3 to 30 GHz).
Ship Earth Station (SES)
An earth station in the maritime mobile
A station in the terrestrial radio
Operating method in which transmission is made possible alternatively in each direction of a telecommunication channel, for example, by means of manual control (see single
The same frequency used for transmission and reception (simplex).
Standard Marine Communication Phrases.
Safety of Life at Sea. International Convention for the Safety of Life at Sea.
Safety of Life at Sea Convention as adopted by the IMO, and accepted by contracting governments.
Ship Security Alert System. A system fitted under Regulation 6 of SOLAS chapter XI
Single Side Band mode of emission using amplitude modulation, where one sideband is reduced, suppressed or fully removed.
Sea Safety Message. A type of coastal warning referring to hazards which are considered to be of a temporary nature, eg. floating logs, temporary buoys, etc, usually broadcast for a defined period.
Short Safety Related Messaging. A text
Seafarers’ Training, Certification and Watchkeeping (Code and International Convention on).
Telemedical Maritime Advice Services.
Transmitter or transmit frequency
Ultra High Frequency. (300 to 3 000 MHz)
Uninterruptible Power Supply.
Upper Sideband mode of emission. A form of single sideband emission where only the upper sideband is transmitted.
Temps Universel Coordonné (French). Coordinated Universal time (replaces Greenwich Mean Time (GMT) for practical purposes).
Visual Display Unit.
Very High Frequency. (30 to 300 MHz)
Very Low Frequency. (30 to 300 kHz)
A unit of electric potential and electromotive force. Equal to the difference of electric potential between two points on a conducting wire, carrying a constant current of one ampere when the power dissipated between the points is one watt. The symbol for the volt(s) is V.
Vessel Traffic Service. IMO Resolution A.857 (20), defines a Vessel Traffic Service (VTS) as ‘a service implemented by a Competent Authority that is designed to improve safety and efficiency of vessel traffic, and to protect the environment. The service shall have the capability to interact with traffic and respond to traffic situations developing situations in the VTS area’. It is referenced in SOLAS Chapter V, Regulation 12.
Wireless telegraphy (i.e. Morse code).
the power required to do work at the rate of 1 joule per second, which is equal to the power dissipated in an electric circuit in which a potential difference of 1 volt causes a current of 1 ampere to flow. The symbol for watt(s) is W.
Who Are You? A telex command used to request the Answerback from another telex machine.
World–wide Met–Ocean Information and Warning Service. A service established by the World Meteorological Organisation for the purpose of coordinating the transmissions of meteorological warnings in defined geographical areas.
World–wide Navigational Warning Service. A service established by the International Hydrographic Organisation for the purpose of coordinating the transmissions of navigational warnings in defined geographical areas.