The spectral compressor compresses a pre-selected portion of the high frequency band and maps the compressed high frequency band to a lower band limited frequency range.

频谱压缩器压缩高频频带的预选择部分，并将压缩的高频频带映射到较低的有限带宽频率范围。

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But those bootleg versions have a more limited frequency range and can only receive signals, not transmit them.

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