The paper also introduces the evolution of control mode in frequency transducer, and demonstrated the principles of choosing frequency transducer in air conditioning projects through a case study.

述及变频器控制方式的演进，并通过实例说明在暖通空调工程中变频器的选用原则。

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There is not one case of transmission on our sardine-packed public-transport system or through the air-conditioning systems in office buildings.

ECONOMIST: Preferential treatment