When a vessel signals her distress by means of a gun or other explosive signal，the firing should be at intervals of approximately（）.

The generators on your rig have shut down，leaving you without navigation lights. Which emergency signal would you transmit over the VHF radio to alert vessels in the area of your predicament? （）

If no distress acknowledgement is received（）a DSC distress call transmission, then the ship in distress may repeat the DSC distress call attempt after a delay of between 3.5 and 4.5 minutes from the beginning of the initial call.

（）is an area within the radiotelephone coverage of at least one VHF coast station in which continuous Digital Selective Calling is available.

Distress signal are always stored in the memory so as to start（）.

Distress signal are always stored in the memory so as to start（）.

为什么VHF通信属于近距离通信？

船用VHF通信设备属于（）距离的通信设备。

Jitter is an unwanted variation of one or more characteristics of a periodic signal in electronics and telecommunications and（）refers to call issues that cause variations in timing or time of arrival.

DSC distress acknowledgements are normally transmitted by（）in respond to a receiver DSC distress call.

Which channel is designated for VHF Digital Selective Calling?

Which action should you take after sending a false distress alert on VHF?（）