A Method of Frame Separation in the Time-Division-Multiplexed Delta Modulation System

A method to shorten the time required for the frame separation in the time-division-multiplexed delta modulation system is described. Employing successive "1"s as the sync pattern, the system detects the sync channel out of the delta modulated information pulses which occur at the rate of one half in average. Using a memory device with the capacity of one frame, the detection is performed by taking successive frame correlation of each channel in parallel. For example, in the system with 20 channels, the frame separation is established in approximately six frame periods. The system includes such facilities as to stabilize the frame separation against the error of the sync pattern and against the occurrence of the information pattern similar to the sync pattern. A possibility for shortening further the time required for the frame separation is also described. The method is to modify, at the transmitting end, the information pattern when it appears the same as the sync pattern. The proposed system is also applicable to such cases when the sync pattern consists of several bits by providing a shift register to detect the pattern at the input of the memory device.