A high frequency pulse-time modulation (PTM) signal generator employs four or more high frequency oscillators which are mutually locked uniquely either in a symmetric mode or an antisymmetric mode by means of a plurality of electronic phase shifters. The output signals from the oscillators are cascaded together to form a PTM output through control of the electronic phase shifters which shift the mutual locking of the oscillators back and forth between the symmetric and antisymmetric modes. Magic-tees or other combining elements are employed to combine the oscillator output signals so that an output pulse is generated when the oscillators are locked in the symmetric mode and a zero level output is generated when the oscillators are locked in the antisymmetric mode.