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Time dependent, variable amplitude threshold output circuit for frequency variant and frequency invariant signal discrimination
Time dependent, variable amplitude threshold output circuit for frequency variant and frequency invariant signal discrimination
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机译:时间相关的可变幅度阈值输出电路,用于频率变化和频率不变信号的识别
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摘要
A voice signal compression system (10) includes a variable gain amplifier (14) for amplifying a voice input signal (12) at a gain dependent on a variable control voltage (32). A driver (18) receives the amplified input signal and supplies a power-boosted output signal (20) to an acoustic output transducer, a peak detecting comparator (24), and to a thresold reset timer (26). The comparator (24) produces a digital output that triggers an attack/decay timer (30) which produces the control voltage (32). The comparator (24) initially is set to a high threshold state by the threshold reset timer (26). As the levels and peaks of the input signal (12) increase, the comparator (24) begins to trigger digital pulses to the attack/decay timer (30), and the threshold reset timer (26) begins measuring the duration of the signal which exceeds the threshold of the comparator (24). If the level of the power-boosted output signal (20) exceeds the threshold of the comparator (24) for a preselected time, then the compression threshold of the comparator (24) is switched to a lower level. The threshold remains low until the continuous signal is removed whereupon the comparator (24) is reset to its higher threshold.
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