a time shared multiport conference arrangement includes an additive pcm speaker circuit . the additive pcm speaker circuit eliminates the need for loudest speaker detection and the last speaker memory of conventional conferencing arrangements . the additive pcm speaker circuitry operates in an on - line , real time environment to allow rapid summing of speakers &# 39 ; pcm voice samples . since the pcm voice samples are logarithmic in nature , they are not directly combinable . the additive pcm speaker circuitry provides a storage medium which is preprogrammed with resultant values . these resultant values each correspond to a pcm addition of the values of two input speaker &# 39 ; s pcm voice samples . the additive pcm speaker circuit simplifies the complex processing logic usually associated with loudest speaker detection systems and thereby improves the real time operation of the conferencing arrangement .