中间层由带以太网接口的现场控制单元设备PLC组成；

The middle layer is composed of the field control unit device PLC with Ethernet interfaces.

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次级带轮旋转传感器（41）检测输出轴 （22）的转速（54）并将其输出到控制单元（9）。

The secondary sheave rotation sensor (41) detects a rotational speed (54) of the output shaft (22d) and outputs to the control unit (9).

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