Phase-modulation data sets for serial transmission at 2,000 and 2,400 bits per second

Data sets employing phase modulation (PM) techniques are described. A brief description of the operation of the set follows: Pairs of serial binary digits, called dibits, are encoded by the transmitter to generate line signal elements conveying information by means of relative shifts of the carrier-frequency phase angle. This relative phase shift allows the use of differentially coherent detection in the receiver. In-phase and quadrature components of the received line signal are delayed for a period of time corresponding to one signal element and are then modulated with the incoming signal to produce baseband data signals. Bit synchronization timing circuits in the receiver continuously recover a timing wave from the line signal. The operation of this circuit does not depend on message content and is not affected by carrier shift.