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單項選擇題

Usually the panels are interlocked with （） so that the devices can be made dead before the doors are opened.

A.protective earth
B.isolators
C.ground switch
D.circuit-breakers

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單項選擇題

In （） the control action is independent on(of) the output.

A.a closed loop control system
B.an open loop control system
C.a boiler control system
D.a steering gear control system

單項選擇題

This arrangement is （） if the elements are directly connected to one another and the control action takes place without human involvement.

A.a manual closed loop
B.a manual opened loop
C.an automatic closed loop
D.an automatic opened loop

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