The problem of increasing the efficiency of the synchronization systems in equipment for generating and stabilizing frequency networks is an important one in communications engineering. System efficiency is assessed on the basis of speed of response, level of sidebands in the output, accuracy with which frequency and phase can be set, manufacturing requirements, and reliability. One way of increasing the efficiency is to use combined (analog-digital) control systems. Paper investigates the dynamic properties of a continuous model of an analog-digital frequency-phase automatic control system containing two control circuits. The two-circuit system uses two interconnected synchronization systems: phase and freqency. The frequency tuning is accomplished with the aid of digital elements.