Abstract: A demodulating apparatus receives a differential phase shift keyed analog signal which is coupled to the input of a voltage controlled oscillator. The voltage controlled oscillator generates a plurality of pulses at a frequency which is proportional to the amplitude of the analog signal. The pulses are counted during in-phase intervals and intervals which are quadrature phase related to the in-phase intervals. The signs of the differences between (i) the number of in-phase and quadrature phase interval pulses counted during a first bit rate interval and (ii) a reference pulse count number, are determined. The signs of the differences between (i) the in-phase and quadrature phase pulses counted during a second bit rate interval, which follows the first bit rate interval, and (ii) the reference count number, are also determined.