AIS Transponder (Class A)
A Class A AIS transponder automatically broadcasts a ship's identity, position, course and speed to other vessels and shore stations every few seconds while under way, and receives the same data back, functioning as mandatory collision-avoidance equipment rather than an optional aid.
Read more — AIS Transponder (Class A) explained ▾
What Makes a Class A AIS Transponder Different
A Class A AIS transponder transmits automatically and continuously, position, course, speed, heading, rate of turn and voyage data, using dedicated VHF channels, without needing anyone to key a call. Reporting intervals shorten automatically as speed or manoeuvring status changes, from as long as three minutes at anchor down to about two seconds when a ship is turning at speed. That automatic, high-frequency, mandatory-carriage behaviour is what separates Class A from Class B, the lower-power, lower-priority transponder fitted to smaller commercial and leisure craft, which transmits less often and yields channel access to Class A traffic. Class A is the SOLAS-mandated type; Class B is never an acceptable substitute for a vessel required to carry AIS.
Main Components
VHF transceiver
Transmits and receives on the two internationally designated AIS VHF channels, switching automatically between them and monitoring for regional channel changes broadcast by shore authorities.
GNSS receiver
An internal or externally fed GPS/GNSS position source providing the position, course and speed data transmitted in each report; accuracy here directly affects the reliability of every ship relying on that data for collision avoidance.
Minimum keyboard and display (MKD)
The bridge unit used to enter voyage-related data, destination, ETA, cargo category, number of persons on board, and to view received traffic; many ships instead interface AIS data into the ECDIS or radar and use the MKD only as backup.
Pilot plug
A standardized connector giving a pilot's portable navigation unit direct access to the ship's AIS and other sensor data on boarding.
Sensor interfaces
Inputs from the gyrocompass, rate-of-turn indicator and speed log feed additional fields into the AIS broadcast beyond what GNSS alone provides.
Selection and Sizing
- Type approval matching the flag state's accepted equipment list, since AIS is SOLAS-mandated and not a discretionary fit-out choice
- Integration options with the ship's ECDIS, radar and VDR, since AIS data is now expected to overlay directly on the primary navigation displays
- Pilot plug provision and location, positioned for practical access when a pilot boards
- Long-range AIS capability where trading patterns or company policy call for satellite-relayed position reporting beyond VHF range
Regulations and Class
SOLAS Chapter V requires AIS Class A carriage on all ships of 300 gross tonnage and above engaged on international voyages, cargo ships of 500 gross tonnage and above not engaged on international voyages, and all passenger ships regardless of size. The transponder must remain in operation at all times except where its operation might compromise the safety or security of the ship, a decision the master documents in the log. Static data such as ship name, call sign, IMO number and dimensions, and voyage data such as destination, ETA and draught, must be kept current, since inaccurate AIS data undermines the collision-avoidance purpose of the whole system for every vessel receiving it.
Typical Faults
| Fault | Cause | Consequence |
|---|---|---|
| Incorrect or stale voyage data | Destination, ETA or draught not updated after departure or cargo change | Other vessels and VTS act on wrong information, undermines traffic management |
| Position jumps or freezes on other ships' displays | GNSS signal loss or degraded antenna reception | Loss of reliable collision-avoidance data at the worst possible time |
| Transponder switched off without justification | Crew silencing AIS believing it aids security or avoids attention | SOLAS non-compliance, Port State Control deficiency, real collision risk to other traffic |
| Static data errors such as wrong MMSI, ship type or dimensions | Incorrect programming at installation, never corrected afterward | Persistent identification confusion across every vessel and VTS that receives the signal |
What to Look for in a Supplier
- Current type approval matching the flag state's accepted list and the applicable IMO performance standard
- Straightforward integration with the ship's existing ECDIS, radar and VDR rather than a standalone display nobody actually uses
- GNSS antenna placement guidance suited to the vessel's superstructure, since shadowing degrades position quality
- Support for correcting static and voyage data quickly, since errors here are a compliance issue as much as a technical one
Check static and voyage data every time cargo, destination or draught changes; an AIS transponder broadcasting confidently wrong information is arguably worse than one that is silent, because everyone else trusts it.
23 manufacturers · 39 models
Furuno
5- GNSS, heading or speed-input failure causes invalid dynamic data and sensor alarms
- VHF antenna or feeder faults reduce transmit and receive range and may trigger built-in-test warnings
- Incorrect static or voyage data results in wrong vessel information being transmitted
- Power-supply or network faults cause unit resets, blank displays or loss of target data to bridge systems
- Internal transceiver or timing faults cause transmission alarms or missing nearby targets
- GNSS, heading or speed-input failure causes invalid dynamic data and sensor alarms
- VHF antenna or feeder faults reduce transmit and receive range and may trigger built-in-test warnings
- Incorrect static or voyage data results in wrong vessel information being transmitted
- Power-supply or network faults cause unit resets, blank displays or loss of target data to bridge systems
- Internal transceiver or timing faults cause transmission alarms or missing nearby targets
- GNSS, heading or speed-input failure causes invalid dynamic data and sensor alarms
- VHF antenna or feeder faults reduce transmit and receive range and may trigger built-in-test warnings
- Incorrect static or voyage data results in wrong vessel information being transmitted
- Power-supply or network faults cause unit resets, blank displays or loss of target data to bridge systems
- Internal transceiver or timing faults cause transmission alarms or missing nearby targets
- GNSS, heading or speed-input failure causes invalid dynamic data and sensor alarms
- VHF antenna or feeder faults reduce transmit and receive range and may trigger built-in-test warnings
- Incorrect static or voyage data results in wrong vessel information being transmitted
- Power-supply or network faults cause unit resets, blank displays or loss of target data to bridge systems
- Internal transceiver or timing faults cause transmission alarms or missing nearby targets
- Antenna, feeder or casing damage reduces communication or locating performance and may cause self-test faults
- Battery, emergency-power or power-supply deterioration causes resets, low-voltage alarms or failure to operate
- Water ingress or corrosion causes intermittent operation, damaged connectors or internal faults
- Configuration, registration or identity errors cause incorrect vessel or beacon information
- Internal transceiver, display or control faults cause failed self-tests, missing communications or unavailable emergency functions
JRC
4- GNSS, heading or speed-input failure causes invalid dynamic data and sensor alarms
- VHF antenna or feeder faults reduce transmit and receive range and may trigger built-in-test warnings
- Incorrect static or voyage data results in wrong vessel information being transmitted
- Power-supply or network faults cause unit resets, blank displays or loss of target data to bridge systems
- Internal transceiver or timing faults cause transmission alarms or missing nearby targets
- GNSS, heading or speed-input failure causes invalid dynamic data and sensor alarms
- VHF antenna or feeder faults reduce transmit and receive range and may trigger built-in-test warnings
- Incorrect static or voyage data results in wrong vessel information being transmitted
- Power-supply or network faults cause unit resets, blank displays or loss of target data to bridge systems
- Internal transceiver or timing faults cause transmission alarms or missing nearby targets
- Sensor, antenna or transducer fault, typically indicated by missing, unstable or implausible navigation data
- Power-supply or processor failure, typically indicated by blank display, rebooting or unavailable function
- Network/interface fault, typically indicated by missing data on connected bridge systems or communication alarms
- Cable/connector corrosion or water ingress, typically indicated by intermittent operation or signal loss
- Recording/storage or software fault on recorder-type equipment, typically indicated by data gaps, recording alarms or failed playback
- Loss of supply power from a tripped breaker, failed power unit, loose connection, or depleted reserve battery causes a dead unit, rebooting, or failure to transmit
- Antenna, feeder, connector, or matching fault caused by corrosion, water ingress, or physical damage results in poor range, failed transmission, or weak received signals
- Control-panel, display, keypad, or software faults can prevent channel selection, message handling, or normal operator input
- Interface or position-data failure caused by wiring, configuration, or sensor faults can remove position information or connected-system data
- Internal transmitter, receiver, or modem faults caused by component ageing or overheating can produce intermittent communication, alarms, or inability to establish a link
Kongsberg Maritime
3- Loss of primary or reserve power from a tripped breaker, failed power unit, loose connection, or depleted battery causes a dead unit, rebooting, or failed transmission
- Antenna, feeder, connector, or matching faults from corrosion, water ingress, or physical damage cause poor range or weak received signals
- Control-panel, display, keypad, or software faults prevent channel selection, message handling, or operator input
- Interface or position-data failure from wiring, configuration, or sensor faults removes position or connected-system data
- Internal transmitter, receiver, or modem faults from component ageing or overheating cause intermittent communication, alarms, or inability to establish a link
- Sensor, antenna or transducer fault caused by damage, fouling, water ingress or electronics failure, resulting in missing, unstable or implausible navigation data
- Power-supply failure caused by breaker, converter or wiring faults, resulting in loss of indication or repeated restarts
- Network or interface failure caused by damaged cabling, port faults or configuration changes, resulting in loss of data to connected bridge systems
- Display, processor or control failure caused by hardware or software faults, resulting in frozen, blank or unavailable functions
- Calibration, alignment or configuration error caused by incorrect setup or maintenance, resulting in persistent disagreement with independent references
- Sensor, antenna or transducer fault, typically indicated by missing, unstable or implausible navigation data
- Power-supply or processor failure, typically indicated by blank display, rebooting or unavailable function
- Network/interface fault, typically indicated by missing data on connected bridge systems or communication alarms
- Cable/connector corrosion or water ingress, typically indicated by intermittent operation or signal loss
- Recording/storage or software fault on recorder-type equipment, typically indicated by data gaps, recording alarms or failed playback
Sailor
3- Loss of primary or reserve power from a tripped breaker, failed power unit, loose connection, or depleted battery causes a dead unit, rebooting, or failed transmission
- Antenna, feeder, connector, or matching faults from corrosion, water ingress, or physical damage cause poor range or weak received signals
- Control-panel, display, keypad, or software faults prevent channel selection, message handling, or operator input
- Interface or position-data failure from wiring, configuration, or sensor faults removes position or connected-system data
- Internal transmitter, receiver, or modem faults from component ageing or overheating cause intermittent communication, alarms, or inability to establish a link
- Loss of supply power from a tripped breaker, failed power unit, loose connection, or depleted reserve battery causes a dead unit, rebooting, or failure to transmit
- Antenna, feeder, connector, or matching fault caused by corrosion, water ingress, or physical damage results in poor range, failed transmission, or weak received signals
- Control-panel, display, keypad, or software faults can prevent channel selection, message handling, or normal operator input
- Interface or position-data failure caused by wiring, configuration, or sensor faults can remove position information or connected-system data
- Internal transmitter, receiver, or modem faults caused by component ageing or overheating can produce intermittent communication, alarms, or inability to establish a link
- Loss of primary or reserve power from a tripped breaker, failed power unit, loose connection, or depleted battery causes a dead unit, rebooting, or failed transmission
- Antenna, feeder, connector, or matching faults from corrosion, water ingress, or physical damage cause poor range or weak received signals
- Control-panel, display, keypad, or software faults prevent channel selection, message handling, or operator input
- Interface or position-data failure from wiring, configuration, or sensor faults removes position or connected-system data
- Internal transmitter, receiver, or modem faults from component ageing or overheating cause intermittent communication, alarms, or inability to establish a link
Digital Yacht
2- GNSS, heading or speed-input failure causes invalid dynamic data and sensor alarms
- VHF antenna or feeder faults reduce transmit and receive range and may trigger built-in-test warnings
- Incorrect static or voyage data results in wrong vessel information being transmitted
- Power-supply or network faults cause unit resets, blank displays or loss of target data to bridge systems
- Internal transceiver or timing faults cause transmission alarms or missing nearby targets
- GNSS, heading or speed-input failure causes invalid dynamic data and sensor alarms
- VHF antenna or feeder faults reduce transmit and receive range and may trigger built-in-test warnings
- Incorrect static or voyage data results in wrong vessel information being transmitted
- Power-supply or network faults cause unit resets, blank displays or loss of target data to bridge systems
- Internal transceiver or timing faults cause transmission alarms or missing nearby targets
em-trak
2- Antenna, feeder or casing damage reduces communication or locating performance and may cause self-test faults
- Battery, emergency-power or power-supply deterioration causes resets, low-voltage alarms or failure to operate
- Water ingress or corrosion causes intermittent operation, damaged connectors or internal faults
- Configuration, registration or identity errors cause incorrect vessel or beacon information
- Internal transceiver, display or control faults cause failed self-tests, missing communications or unavailable emergency functions
- Loss of primary or reserve power from a tripped breaker, failed power unit, loose connection, or depleted battery causes a dead unit, rebooting, or failed transmission
- Antenna, feeder, connector, or matching faults from corrosion, water ingress, or physical damage cause poor range or weak received signals
- Control-panel, display, keypad, or software faults prevent channel selection, message handling, or operator input
- Interface or position-data failure from wiring, configuration, or sensor faults removes position or connected-system data
- Internal transmitter, receiver, or modem faults from component ageing or overheating cause intermittent communication, alarms, or inability to establish a link
SAAB
2- Sensor, antenna or transducer fault, typically indicated by missing, unstable or implausible navigation data
- Power-supply or processor failure, typically indicated by blank display, rebooting or unavailable function
- Network/interface fault, typically indicated by missing data on connected bridge systems or communication alarms
- Cable/connector corrosion or water ingress, typically indicated by intermittent operation or signal loss
- Recording/storage or software fault on recorder-type equipment, typically indicated by data gaps, recording alarms or failed playback
- Sensor or antenna degradation caused by contamination, damage, ageing or poor exposure can produce missing, unstable or implausible data
- Connector, cable or network faults caused by vibration, corrosion or disturbed terminations can cause intermittent data loss or interface alarms
- Power-supply or internal electronics failure caused by ageing, heat or poor ventilation can result in resets, blank indications or complete loss of function
- Configuration or software errors after service or replacement can cause incorrect data, rejected inputs or loss of communication with other bridge equipment
- Mechanical damage or water ingress at exposed components can lead to erratic readings, repeated alarms or loss of the affected channel
Transas Marine
2- Loss of primary or reserve power from a tripped breaker, failed power unit, loose connection, or depleted battery causes a dead unit, rebooting, or failed transmission
- Antenna, feeder, connector, or matching faults from corrosion, water ingress, or physical damage cause poor range or weak received signals
- Control-panel, display, keypad, or software faults prevent channel selection, message handling, or operator input
- Interface or position-data failure from wiring, configuration, or sensor faults removes position or connected-system data
- Internal transmitter, receiver, or modem faults from component ageing or overheating cause intermittent communication, alarms, or inability to establish a link
- Loss of primary or reserve power from a tripped breaker, failed power unit, loose connection, or depleted battery causes a dead unit, rebooting, or failed transmission
- Antenna, feeder, connector, or matching faults from corrosion, water ingress, or physical damage cause poor range or weak received signals
- Control-panel, display, keypad, or software faults prevent channel selection, message handling, or operator input
- Interface or position-data failure from wiring, configuration, or sensor faults removes position or connected-system data
- Internal transmitter, receiver, or modem faults from component ageing or overheating cause intermittent communication, alarms, or inability to establish a link
Vesper Marine
2- GNSS, VHF antenna or transceiver fault caused by damage, poor connections or electronics failure, resulting in missing targets, transmission alarms or invalid own-ship data
- Power-supply failure caused by breaker, converter or wiring faults, resulting in loss of the equipment or repeated restarts
- Network or interface failure caused by damaged cabling, port faults or configuration changes, resulting in loss of data to connected systems
- Display, processor or control failure caused by hardware or software faults, resulting in frozen indications, alarms or unavailable functions
- Incorrect configuration or time, position or sensor input caused by setup or upstream faults, resulting in misleading or incomplete information
- Sensor, antenna or transducer fault caused by damage, fouling, water ingress or electronics failure, resulting in missing, unstable or implausible navigation data
- Power-supply failure caused by breaker, converter or wiring faults, resulting in loss of indication or repeated restarts
- Network or interface failure caused by damaged cabling, port faults or configuration changes, resulting in loss of data to connected bridge systems
- Display, processor or control failure caused by hardware or software faults, resulting in frozen, blank or unavailable functions
- Calibration, alignment or configuration error caused by incorrect setup or maintenance, resulting in persistent disagreement with independent references
Alltek Marine
1- GNSS, VHF antenna or transceiver fault caused by damage, poor connections or electronics failure, resulting in missing targets, transmission alarms or invalid own-ship data
- Power-supply failure caused by breaker, converter or wiring faults, resulting in loss of the equipment or repeated restarts
- Network or interface failure caused by damaged cabling, port faults or configuration changes, resulting in loss of data to connected systems
- Display, processor or control failure caused by hardware or software faults, resulting in frozen indications, alarms or unavailable functions
- Incorrect configuration or time, position or sensor input caused by setup or upstream faults, resulting in misleading or incomplete information
Carmanah Marine
1- Antenna, feeder or casing damage reduces communication or locating performance and may cause self-test faults
- Battery, emergency-power or power-supply deterioration causes resets, low-voltage alarms or failure to operate
- Water ingress or corrosion causes intermittent operation, damaged connectors or internal faults
- Configuration, registration or identity errors cause incorrect vessel or beacon information
- Internal transceiver, display or control faults cause failed self-tests, missing communications or unavailable emergency functions
Cobham
1- Loss of supply power from a tripped breaker, failed power unit, loose connection, or depleted reserve battery causes a dead unit, rebooting, or failure to transmit
- Antenna, feeder, connector, or matching fault caused by corrosion, water ingress, or physical damage results in poor range, failed transmission, or weak received signals
- Control-panel, display, keypad, or software faults can prevent channel selection, message handling, or normal operator input
- Interface or position-data failure caused by wiring, configuration, or sensor faults can remove position information or connected-system data
- Internal transmitter, receiver, or modem faults caused by component ageing or overheating can produce intermittent communication, alarms, or inability to establish a link
Comar Systems
1- GNSS, VHF antenna or transceiver fault caused by damage, poor connections or electronics failure, resulting in missing targets, transmission alarms or invalid own-ship data
- Power-supply failure caused by breaker, converter or wiring faults, resulting in loss of the equipment or repeated restarts
- Network or interface failure caused by damaged cabling, port faults or configuration changes, resulting in loss of data to connected systems
- Display, processor or control failure caused by hardware or software faults, resulting in frozen indications, alarms or unavailable functions
- Incorrect configuration or time, position or sensor input caused by setup or upstream faults, resulting in misleading or incomplete information
Orga
1- Loss of primary or reserve power from a tripped breaker, failed power unit, loose connection, or depleted battery causes a dead unit, rebooting, or failed transmission
- Antenna, feeder, connector, or matching faults from corrosion, water ingress, or physical damage cause poor range or weak received signals
- Control-panel, display, keypad, or software faults prevent channel selection, message handling, or operator input
- Interface or position-data failure from wiring, configuration, or sensor faults removes position or connected-system data
- Internal transmitter, receiver, or modem faults from component ageing or overheating cause intermittent communication, alarms, or inability to establish a link
Pharos Marine
1- Sensor, antenna or transducer fault, typically indicated by missing, unstable or implausible navigation data
- Power-supply or processor failure, typically indicated by blank display, rebooting or unavailable function
- Network/interface fault, typically indicated by missing data on connected bridge systems or communication alarms
- Cable/connector corrosion or water ingress, typically indicated by intermittent operation or signal loss
- Recording/storage or software fault on recorder-type equipment, typically indicated by data gaps, recording alarms or failed playback
Pole Star
1- Antenna, feeder or casing damage reduces communication or locating performance and may cause self-test faults
- Battery, emergency-power or power-supply deterioration causes resets, low-voltage alarms or failure to operate
- Water ingress or corrosion causes intermittent operation, damaged connectors or internal faults
- Configuration, registration or identity errors cause incorrect vessel or beacon information
- Internal transceiver, display or control faults cause failed self-tests, missing communications or unavailable emergency functions
Sabik Marine
1- Sensor, antenna or transducer fault, typically indicated by missing, unstable or implausible navigation data
- Power-supply or processor failure, typically indicated by blank display, rebooting or unavailable function
- Network/interface fault, typically indicated by missing data on connected bridge systems or communication alarms
- Cable/connector corrosion or water ingress, typically indicated by intermittent operation or signal loss
- Recording/storage or software fault on recorder-type equipment, typically indicated by data gaps, recording alarms or failed playback
Sealite
1- Sensor or antenna degradation caused by contamination, damage, ageing or poor exposure can produce missing, unstable or implausible data
- Connector, cable or network faults caused by vibration, corrosion or disturbed terminations can cause intermittent data loss or interface alarms
- Power-supply or internal electronics failure caused by ageing, heat or poor ventilation can result in resets, blank indications or complete loss of function
- Configuration or software errors after service or replacement can cause incorrect data, rejected inputs or loss of communication with other bridge equipment
- Mechanical damage or water ingress at exposed components can lead to erratic readings, repeated alarms or loss of the affected channel
Simrad
1- Sensor, antenna or transducer fault, typically indicated by missing, unstable or implausible navigation data
- Power-supply or processor failure, typically indicated by blank display, rebooting or unavailable function
- Network/interface fault, typically indicated by missing data on connected bridge systems or communication alarms
- Cable/connector corrosion or water ingress, typically indicated by intermittent operation or signal loss
- Recording/storage or software fault on recorder-type equipment, typically indicated by data gaps, recording alarms or failed playback
Thrane
1- Sensor or antenna degradation caused by contamination, damage, ageing or poor exposure can produce missing, unstable or implausible data
- Connector, cable or network faults caused by vibration, corrosion or disturbed terminations can cause intermittent data loss or interface alarms
- Power-supply or internal electronics failure caused by ageing, heat or poor ventilation can result in resets, blank indications or complete loss of function
- Configuration or software errors after service or replacement can cause incorrect data, rejected inputs or loss of communication with other bridge equipment
- Mechanical damage or water ingress at exposed components can lead to erratic readings, repeated alarms or loss of the affected channel
Tideland
1- Antenna, feeder or casing damage reduces communication or locating performance and may cause self-test faults
- Battery, emergency-power or power-supply deterioration causes resets, low-voltage alarms or failure to operate
- Water ingress or corrosion causes intermittent operation, damaged connectors or internal faults
- Configuration, registration or identity errors cause incorrect vessel or beacon information
- Internal transceiver, display or control faults cause failed self-tests, missing communications or unavailable emergency functions
True Heading
1- GNSS, VHF antenna or transceiver fault caused by damage, poor connections or electronics failure, resulting in missing targets, transmission alarms or invalid own-ship data
- Power-supply failure caused by breaker, converter or wiring faults, resulting in loss of the equipment or repeated restarts
- Network or interface failure caused by damaged cabling, port faults or configuration changes, resulting in loss of data to connected systems
- Display, processor or control failure caused by hardware or software faults, resulting in frozen indications, alarms or unavailable functions
- Incorrect configuration or time, position or sensor input caused by setup or upstream faults, resulting in misleading or incomplete information
Weatherdock
1- GNSS, VHF antenna or transceiver fault caused by damage, poor connections or electronics failure, resulting in missing targets, transmission alarms or invalid own-ship data
- Power-supply failure caused by breaker, converter or wiring faults, resulting in loss of the equipment or repeated restarts
- Network or interface failure caused by damaged cabling, port faults or configuration changes, resulting in loss of data to connected systems
- Display, processor or control failure caused by hardware or software faults, resulting in frozen indications, alarms or unavailable functions
- Incorrect configuration or time, position or sensor input caused by setup or upstream faults, resulting in misleading or incomplete information