单项选择题
A.Ammeter and changeover switch B.Speed governor device C.Synchroscope D.Wattmeter
（）is not installed on the emergency switchboard.A.Contr...
单项选择题（）is not installed on the emergency switchboard.
A.Control panel B.Paralleling panel C.Load panel D.Busbar
（）can be used to prevent hydraulic system overloaded or...
单项选择题（）can be used to prevent hydraulic system overloaded or keep the pressure of oil outlet from pump constant.
A.Overflow valve B.Reducing valve C.Balancing valve D.Reducing valve or balancing valve
The symbol (GB786√1-93) at right side represents （）A.ov...
单项选择题The symbol (GB786√1-93) at right side represents （）
A.overflow valve B.reducing valve C.relief valve D.sequence valve
