What does the squelch control on a VHF radio do, and what happens if it is set too high?

A. Squelch increases transmit power — set it high in poor conditions for better range

B. Squelch has no effect on received signals — it only reduces battery consumption

C. Squelch selects which channels are monitored in dual-watch mode

D. Squelch suppresses background noise when no signal is received. Set too high: weak signals (including distress calls from distant vessels) are cut off before reaching the speaker — the radio appears silent even when transmissions are present

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