Abstract: Digital logic apparatus for synthesizing a phase-modulated carrier wave wherein phase shifts between successive carrier-wave segments encode data elements. Carrier-wave segments having different phases are stored in the form of digitally encoded samples in a memory. A digital-to-analog converter is connected to convert sequentially read samples of selected segments into the phase-modulated carrier wave. A combinational logic circuit selects each segment to be addressed according to an applied data element and the phase of the previously selected segment. Means are provided to overlap and blend successively addressed segments to provide smooth phase transitions in the synthesized wave.