Abstract: Presents the features and priciple of the quasi - instantaneous companding technique . Implementation of the technique in a digital multiplexer for both broadcasting and telephone channels , accomplished with linear coding and the digital bit companding method is discussed. The block diagram and part of the circuits of a 12 - 9 bit companding program for a two -channel time sharing broadcast system are given.Experimental results show that the system is simple and practical, offering a satisfactory performance .