前端采集插头接收测试数据，切换继电器电路传递被测电路板信号。

Testing data is received with data acquisition plug, signal from tested circuit board is transferred by circuit of switch relay.

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还有就是，如果我们把信号线的插头接触机箱的金属部分时，音箱就会传出“嗡嗡”的交流声，特别明显。

There is, if we plug the signal line contact of metal parts chassis, the speaker will be news "buzz" the exchange of sound, particularly evident.

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