Similarly, at times, some problems may occur in the system even when there has been no check engine light or trouble code signal.

同样地，有时，有些故障可能在系统中已经产生但并没有“检查发动机”灯或故障码信号显示。

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The CATV charge and control system has excellent compatibility with other signals and no astriction in signal format, so you doesn't need to worry about its future.

CAT V收费控制系统有很好的信号兼容性，对信号的格式没有要求，不会因信号处理方式和信息量的多少而更新淘汰。

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The system must reject noise even when there is no signal and, in fact, this is usually how system noise testing is done.

不过，这种对称性对于噪声抑制没有意义，系统应当能在没有信号时也能抑制噪声的发生（侵入），事实上，这通常是系统测试所需要做的。

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