a current source based multilevel bus driver and converter suitable to simultaneously insect precise magnitudes of current from multiple locations into common lines of a bus and then detect analog sums of the net current . the analog current sums so detected are decoded into digital equivalents corresponding to the respective current injection sources . in a typical application the current source drivers and converter are located on separate integrated circuit chips . the reference node common to all the chips allows a reference generator on each chip to precisely define bias and transmitted current levels suitable to ensure precise values of injected current and to accurately differentiate between analog current levels in each line as an aspect of conversion into digital form and attribution as to origin .