Loudspeaker telephone
AssigneeCompagnie Industrielle des Telecommunications Cit-Alcatel
InventorsSolange Bernard, Dominique Lajotte, Francois Michelon, Jacques Sourgens
Life of this patent
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Abstract
A loudspeaking telephone has a differential coupler (3) connecting a two-way two-wire telephone line (4) to separate transmission and reception channels (1 and 2 respectively) including respectively a microphone (5) and a loudspeaker (7). A first transversal filter (10) synthesizes an acoustic echo signal ya which is subtracted from the microphone signal to deliver a substantially echo-free signal to the transmission channel. Likewise a second transversal filter (11) synthesizes an electrical echo signal to deliver a substantially echo-free signal to the reception channel.
Claims11
A loudspeaking telephone comprising:
- a differential coupler for connection to a two-wire telephone line and including an input and an output;
- a microphone circuit having its output connected to the input of a transmission channel whose output is connected to the input of the differential coupler;
- a loudspeaker circuit having its input connected to the output of a reception channel whose input is connected to the output of the differential coupler;
- and
- first and second adaptive transversal filter means associated respectively with the transmission channel and with the reception channel;
- both of the adaptive transversal filter means having controlled weighting and filter coefficients, and including:
- a signal combining circuit;
- a transversal filter having a first signal input connected to receive the output signal of the associated signal combining circuit;
- said transversal filter further having a second signal input connected to receive the output signal of the other channel;
- and
- a signal output connected to deliver a filter output signal to the signal combining circuit;
- the signal combining circuit being connected in series with the other channel to receive the input signal of the other channel, to combine it with the filter output signal and to apply the combined signal to the remainder of the said other channel;
- and
- a control input for controlling the coefficients connected to receive the combined signal;
- whereby said first adaptive transversal filter means uses the output signal of the reception channel to synthesise any acoustic echo signal component present in the output from the microphone circuit, and its combining circuit substracts the real and the synthetic acoustic echo signal components from each other to reduce the acoustic echo signal component in the transmission channel to a residual level;
- and likewise the second adaptive transversal filter means uses the output signal of the transmission channel to synthesise any electrical echo signal component present in the output from the differential coupler, and its combining circuit subtracts the real and the synthetic electrical echo signal components from each other to reduce the electrical echo signal component in the reception channel to a residual level.
Dependencies are inferred from the claim text.