Abstract: A phase modulation low power integrated circuit communications arrangement which employs a frequency shift oscillator is disclosed. The frequency shift oscillator operates normally at a first frequency and is keyed to a second frequency for brief intervals to introduce cumulative first frequency phase change in an output signal. Subquadrature and larger increments of phase shift, spurious frequency component rejection with wave filters, and low power amplification of the modulated signal are also disclosed. Specifically, transitions in either (or both) of a pair of binary input signals cause a 45-degree (or 90-degree) phase shift in the phase-modulated carrier, unlike standard DQPSK modulation.