单项选择题
A.It cannot be used in all parts of the world B.There are 12 functioning GPS satellites at present C.It may be suspended without warning D.Two position lines are used to give a 2D fix
A.Pulse width B.Pulse repetition frequency C.Peak power D.Target brightness
A.Radio communications allow the crane operator to disregard the use of hand signals B.The crane operators and signalman must be familiar with the correct hand signals C.The forward cranes can be operated from the bridge D.The aft cranes can be operated from the aft steering station