Abstract: A linear feedback shift register for use as a SONET data scrambler, operating in accordance with a generating polynomial of order n corresponding to an n by n transition matrix T, comprises k storage cells, where k>n, for producing a k-bit word, and linear feedback interconnections specified by a k by k transition matrix which is the k-th power of a k by k transition matrix constituted by the matrix T extended by k-n additional rows and columns. Specific examples are described for k=8 and k=16.

Abstract: Apparatus for converting binary to quaternary-level signals in which the symbols of selected words are inverted in order to eliminate the d-c component of the signal. In order to reduce the power spectral density at frequencies close to d-c and increase the power spectral density at frequencies close to the Nyquist rate, one word of each frame is selectively inverted relative to another in order to maximize the summation of all the numerical values of the differences between adjacent symbol levels. Thereafter both words of the frame are selectively inverted in order to minimize the running digital sum of the signal.

Abstract: A method and apparatus for converting a binary signal to one having quaternary-level symbols with no d-c component. To achieve this, the running digital sum is limited by selectively inverting words within each frame of (n) symbols. A separate (n+1)th symbol is added to each frame to indicate the selective inversion of the words, so that the correct polarity of the (n) symbols can be re-established.

Abstract: A digital signalling process and apparatus employing multistage charge coupled devices provides a delay structure with a multiplicity of signal paths between an input signal terminal and an output signal terminal. The signal paths impose differing delays such that when the input signal is or contains a periodic waveform whose period is in a predetermined relation to the differences between the delays in the paths, there is reinforcement of the periodic waveform. The charge coupled devices are actuated by clocking pulses and operate so as effectively to sample the reinforced signal at a rate whose period exceeds the period of the periodic waveform. As a result there appears at the output of the apparatus an averaged and time stretched version of the periodic waveform.