What are the international radio silence periods on 2182 kHz and what is their purpose?

A. Silence periods are 30 seconds at H+15 and H+45 on Ch 16 only

B. Three minutes of radio silence at H+00 and H+30 (i.e. at the top and half-past each hour) — during these periods all stations must listen on distress frequencies for any weak distress signals that might otherwise be masked

C. There are no international silence periods — this is an outdated concept replaced by GMDSS

D. Silence periods apply only to MF/HF radio, not to VHF — leisure vessels need not observe them

A. To operate the radar system remotely

B. To broadcast weather forecasts to other vessels

C. To make telephone calls from the vessel to shore

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

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

B. A GPS waypoint identifier used in coastal navigation

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

D. A vessel survey certificate number required by the MCA