The mandatory AIS transponder fitted on SOLAS ships transmitting vessel data at regular intervals and responding to interrogations.
Quick facts
Regulation
SOLAS Chapter V/19
In practice
Class A transponders receive and display the AIS transmissions of other vessels, improving situational awareness particularly in restricted visibility, traffic separation schemes, and port approaches. They are integrated with ECDIS, radar, and VHF DSC systems. Data from AIS networks is also used by vessel traffic services, maritime rescue co-ordination centres, and maritime authorities for traffic monitoring, incident response, and port state control advance notification. Officers must keep the AIS data up to date — particularly navigation status and estimated time of arrival — and must not transmit false information, which is a criminal offence in many jurisdictions.
Regulatory detail & full definition
AIS Class A is the mandatory automatic identification system transponder required by SOLAS Chapter V/19 on all international voyaging vessels of 300 gross tonnage and above, all cargo ships of 500 gross tonnage and above, and all passenger ships. The Class A transponder transmits vessel static data — MMSI, call sign, name, and dimensions — along with dynamic data including position, speed over ground, course over ground, rate of turn, and heading at intervals prescribed by ITU-R Recommendation M.1371. The reporting interval varies from two seconds for vessels manoeuvring to three minutes for vessels at anchor, adapting automatically to the vessel's navigation status.
Class A transponders receive and display the AIS transmissions of other vessels, improving situational awareness particularly in restricted visibility, traffic separation schemes, and port approaches. They are integrated with ECDIS, radar, and VHF DSC systems. Data from AIS networks is also used by vessel traffic services, maritime rescue co-ordination centres, and maritime authorities for traffic monitoring, incident response, and port state control advance notification. Officers must keep the AIS data up to date — particularly navigation status and estimated time of arrival — and must not transmit false information, which is a criminal offence in many jurisdictions.