Abstract: An echo canceler having an FIR filter for removing an echo from a transmission input signal, the echo resulting from a reflection of a received signal through an echo path, and thereby outputting an output signal with the echo cancelled. The echo canceler includes an impulse response estimating system for estimating the impulse response of the echo path at a time t as a function of the received signal, the echo-cancelled output signal, and an estimated impulse response signal, and thereby outputting the estimated impulse response as the estimated impulse response signal; an echo signal estimating system for generating a predicted signal as a function of the estimated impulse response signal and the received signal, and outputting the predicted signal as an estimated echo signal; and a subtractor for subtracting the estimated echo signal from the transmission signal so as to produce the echo-cancelled output signal.

Abstract: An audio bridge for a telephone conference is disclosed. The audio bridge; comprises a channel signal processing unit assigned to at least three channels. Each channel signal processing circuit comprises an echo canceller to cancel an echo signal from the transmitting side fed back to the receiving side, an amplifier and attenuator circuits to adjust levels of an output of the echo canceller and a transmitting signal transmitted through the channel signal processing circuit, an ERL determining circuit to determine an echo cancellation on the basis of the output from the echo canceller and a signal level on the transmitting side, and a gain/loss computing circuit to compute a loss in a predominant voice condition and a gain and a loss in an inferior voice condition.

Abstract: A digital conference circuit for multiplexed voice signals. Each slot for each of the users is further sub-divided into sub-slots for all the users. A selection circuit indicates which originating users are to be connected with which receiving users within a conference. No message is retransmitted to the originator. The received message in a slot is gated according to the selection signal into an adder, also receiving the output of a shift register holding the signals for all sub-slots in one slot. The added signal is shifted into the shift register. Once all the corresponding sub-slots have been added, the output of the shift register is transmitted to the users.