Importance

Loading Importance Indicators...

Abstract

A circuit for blocking reception of in-band frequency-shift keyed (FSK) signals by the reception transducer of a telephone subscriber terminal without requiring muting of the reception transducer. The incoming telephone reception signal, which contains both voice and frequency-shift keyed (FSK) signal components, is processed, e.g., within a digital signal processor (DSP), such that the FSK signal component is substantially cancelled. The incoming telephone reception signal is processed to extract amplitude, frequency and phase information, as well as to recover the FSK data clock. This FSK signal information is then used to generate a replica FSK signal for summing with the incoming telephone reception signal to cancel the FSK signal component. Echo cancellation of the local subscriber voice can also be implemented by adaptively filtering the incoming telephone reception signal in accordance with the outgoing telephone transmission signal and subtracting the resultant signal from the incoming telephone reception signal, thereby canceling the transmission signal echo component.

Loading the Abstract Image...

First Claim