Speech additive distribution equipment for conferencing system

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. The speech audio bridge further comprises audio bridge circuits which add the outputs of the amplifier circuits provided in the channel signal processing circuits except for the one assigned to itself, and a predominant channel detection unit for detecting a predominant channel and inferior channels on the basis of output levels of the amplifier circuits to suitably control the gain and loss of each channel according to the predominant and inferior voice conditions. Thus, this equipment makes it possible to prevent 'singing' due to the variation of the cancellation with time.