單項(xiàng)選擇題The pushbutton on the handset of a ships sound-powered telephone must be depressed to （）.

A.talk then released to listen
B.listen then released to talk
C.both talk and listen
D.ring the station being called


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1.單項(xiàng)選擇題Which of the following statements is true concerning simple parallel resistance circuits?（）

A.The total current flow equals the sum of the individual currents
B.The total current flow equals the reciprocal of the sum of the individual currents
C.The total resistance equals the sum of the individual resistance
D.The total voltage equals the sum of the individual voltages across each resistance

2.單項(xiàng)選擇題Which of the listed items will stop a motor due to a reduction in voltage and restart it when the voltage is restored to normal?（）

A.Low voltage protection circuit
B.Non-renewable link fuse
C.Renewable link fuse
D.Low voltage release circuit

3.單項(xiàng)選擇題Which of the following statements concerning a simple parallel resistance circuit is correct?（）

A.The voltage drop across each resistor is the same
B.The total current flow equals the reciprocal of the sum of the individual currents
C.The total resistance equals the sum of the individual resistances
D.The total voltage equals the sum of the individual voltages across each resistance

4.單項(xiàng)選擇題A ground in an electrical circuit outside the engine room （）.

A.cannot be detected tinder normal conditions
B.is of no consequence to engineering personnel
C.is indicated at the branch circuit breaker panel
D.is indicated by the ground detecting lamps on the main switchboard

5.單項(xiàng)選擇題Grease coatings on electrical contact surfaces increase contact resistance and should be removed with a/an （）.

A.small wire brush
B.compressed air jet
C.clean dry cloth
D.10% solution carbon solvent and water