Patent ID: 6594359
Filing Date: 2003-07-15
Classification: H04M

Abstract:
A circuit for attenuating echo and side tones in a switching system connecting first and second subscribers, comprising:a first linear converter for converting pulse code modulation data generated by said first subscriber into an analog signal; a side tone canceling filter for eliminating the side tones from the analog signal produced by said first linear converter; a clipper for clipping said analog signal rid of said side tones to prevent an amplitude value of said analog signal rid of said side tones from being greater than a predetermined value; a first pulse code modulation converter connected to an output of said clipper for converting the analog signal rid of said side tones passed by said clipper into a refined pulse code modulation data; a second linear converter for converting pulse code modulation data generated by said second subscriber into an analog signal; an echo canceling filter for eliminating the echo from the analog signal produced by said second linear converter; a second pulse code modulation converter for converting the analog signal rid of said echo into a second refined pulse code modulation data; and a communication state detector for detecting the state of the communication between the first and second subscribers so as to control said side tone canceling filter and said echo canceling filter.