What is an AIS Class B transponder and what does it transmit?

A. Class B transmits only in an emergency — it is the leisure equivalent of DSC

B. Class B is the AIS standard for leisure and smaller commercial vessels — it transmits MMSI, vessel name, position, course, speed, and vessel type automatically every 30 seconds (more often when manoeuvring). Received by all AIS displays including ship's radar overlays, chart plotters, and vessel tracking websites

C. Class B requires a dedicated MF/HF radio licence separate from the VHF SRC

D. Class B is receive-only — it shows other vessels but does not transmit your position

A. To send a digitally coded distress alert containing the vessel's MMSI and position automatically to all DSC-equipped stations and the Coastguard

B. To broadcast weather forecasts to other vessels

C. To make telephone calls from the vessel to shore

D. To operate the radar system remotely

A. A GPS waypoint identifier used in coastal navigation

B. Maritime Mobile Service Identity — a unique 9-digit number identifying the vessel; without it a DSC distress alert cannot identify the vessel to rescuers

C. A VHF channel number allocated by Ofcom for distress use only

D. A vessel survey certificate number required by the MCA