| 摘要 |
A digital echo suppression circuit in a four-wire digital telephony circuit having an echo from a local or remote connection to a two-wire circuit or other echo source. The invention incorporates a simple method of using the sample pairs from the first and second sampling circuit to produce a control signal from a control circuit. If the subscriber signal is "louder" than the network signal, then the subscriber signal is passed through. If the network signal is louder than the subscriber signal, the interrupter is activated and a zero level is substituted for the subscriber signal in transmissions toward the network. The invention uses the scheme of comparing instantaneous signal amplitude and using the larger amplitude to set a threshold value. The signal setting the threshold then remains the "loudest" until such time as the other signal can exceed the threshold. The threshold is slowly decremented, but the original signal may refresh the threshold to a higher level if a new peak value replaces the old threshold value with the new peak value. The identity of the input network or subscriber producing the threshold is stored. If the current threshold is the result of a network signal, the interrupter is activated and echo is suppressed. If the current threshold is the result of a network signal, the interrupter is activated and echo is suppressed. If the current threshold is the result of a subscriber signal sample, then the interrupter is deactivated and subscriber signals are transmitted onward toward the network.
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