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Abstract

Hands-free two-way communication is achieved, without the necessity of selectively muting either the sent or received signal and without the generation of interfering acoustical feedback between the speaker and microphone at the hands-free station, by frequency offsetting the audio signal sent from the hands-free station. The audio signal is frequency offset by first modulating the audio signal at a first carrier frequency to produce modulated upper and lower sideband outputs. The modulated upper sideband output is filtered out, and the modulated lower sideband output is coupled to the input of a demodulator. The modulated lower sideband output is then demodulated at a second carrier frequency offset from the first carrier frequency by a predetermined amount. A demodulated upper sideband output and lower sideband output is thus generated. The demodulated upper sideband output is filtered out, and the demodulated lower sideband output is provided for transmission or broadcast in the two-way communication. The demodulated lower sideband output is identical to the original input audio signal with the exception that it has been frequency offset by an amount equal to the predetermined amount of frequency offset between the first and second carrier frequencies. In the event of cross-talk or any feedback within the two-way communication loop, each transmission of the information is thus frequency offset, and the establishment of interfering feedback loops is thereby avoided.

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