控温电路采用四端电阻自平衡电流环路，从而保证其电气和温度均处于闭环状态。

The control circuit is a self-balancing current loop which makes use of a four-terminal resistor of nickel wire to assure a close-loop both electrically and thermally.

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依据四端网络的基本原理，利用力电类比的方法，给出了复合变幅杆的等效电路图；

Based on the theory of four-end network, the equivalent electric circuit diagrams of the horn are given by using the analogous method between methanical force and electric.

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