单项选择题
A.dedicated system B.MSI broadcasts C.518KHZ D.channel 16
The WWNWS is a coordinated global service for the broad...
单项选择题The WWNWS is a coordinated global service for the broadcast by radio of vital information on（）to marine navigation.
A.ship’s movement B.safety C.ship’s management D.hazards
With the help of modern technology, ships are able to r...
单项选择题With the help of modern technology, ships are able to receive automated broadcast of safety messages（）.
A.by day or at night B.almost round the clock C.somewhat and sometime D.from sunrise and sunset
A radio determination system based on the comparison of...
单项选择题A radio determination system based on the comparison of reference signals with radio signals reflected,or retransmitted from the position to be determined,is（）.
A.DF B.Radar System C.DSC System D.COSPAS-SARSAT
