动车组累计备用时间不超过48H可上线运行。
An isotherm is（）. a line on a weather map connecting equal points of both temperature and pressure。 an instrument that measures the climatological effects of temperature。 a line connecting points of equal barometric pressure on a weather map。 a line connecting points of equal temperature on a weather ma。
CRH2型动车组英文代号ARf、APU分别指的是蓄电池单元和辅助电源装置。
An intermediate spring is（）. fitted in each leg of the towing bridle。 generally located between the "fishplate" and the main towing hawser。 secured at the "H" bitts。 usually made of manila hawser。
The closed-loop system differs from the open-loop system by（） the lack of a feedback。 the presence of a feed back。 the lack of a computer。 the presence of a computer。
A feedback is an input（）
