To operate a centrifugal fire pump at reduced capacity, you should （）.

单项选择题An AC synchronous transmission type remote steering control system consists of a （）.

A.transmitter at the steering station and a receiver at the steering engine
B.reversible motor at the steering station geared to the steering pumps
C.small induction motor on the bridge which controls the redder through pulleys
D.variable displacement hydraulic pump driven by a reversible DC motor

单项选择题In which of the areas listed would you expect to find the highest salt concentration in a flash evaporator?（）

A.Distiller air ejector cooling medium
B.Saltwater heater discharge
C.First-stage internal feed box
D.Second-stage internal feed box

单项选择题The component of a refrigerating system in which the refrigerant vaporizes and absorbs heat is known as the （）.

A.condenser
B.vapor generator
C.accumulator
D.evaporator

单项选择题The low pressure side of a refrigeration system is considered to exist from the （）.

A.expansion valve to the compressor
B.receiver to the expansion coil
C.expansion valve to the evaporator
D.condenser to the expansion valve

单项选择题If the electric motor driving an air compressor fails to start, the cause may be a （）.

A.leaking unloader
B.tripped circuit breaker
C.control line leak
D.defective pop valve