Multilevel code signal transmission system

Claim 1

A digital information communication system comprising: a transmitting apparatus for converting each block of (nxm) binary bits in a binary signal into corresponding blocks of n multilevel digits, each of said multilevel digits being (2m+k)level digit, where n, m and k are positive integers, and for transmitting said blocks of n multilevel digits, said apparatus comprising, a. first means for converting m(n-1)+1 of said binary bits in a block into n-1 level-indicating signals consisting of one or more binary characters, where each one of said level-indicating signals indicates one of (2m+k) levels being symmetrical about zero, b. second means for converting the remaining m-1 binary bits of said block of (nxm) binary bits into a single level-indicating signal, said second means being adapted to convert said m-1 bits into non-zero level indicating signals of a first polarity, c. polarity inversion means responsive to a polarity inversion control signal for converting each level-indicating signal from said first and second means into an output level-indicating signal, respectively, wherein corresponding input and output level-indicating signals indicate equal amplitude opposite polarity levels, and responsive to the absence of said polarity inversion control signal for passing said level-indicating signals from said first and second means to the output thereof without polarity inversion, d. means for converting n simultaneously occurring polaritycontrolled level-indicating signals from said polarity inversion means into n serial (2m+k)-level digits, said latter digits having respective amplitudes and polarities corresponding to said polarity-controlled level-indicating signals; and e. convolution means for generating said polarity inversion control signal in response to the algebraic sum of the levels indicated by the most recent block of said n level-indicating signals from said first and second means being of the same polarity as the algebraic sum of the prior said multilevel digits, a receiving apparatus for receiving said blocks of n multilevel digits and for reconverting them back into blocks of (n X m) binary bits, including, f. means responsive to each received multilevel digit for generating a level-representing signal representing the amplitude and polarity of said digit, g. means responsive to said received multilevel digits for generating timing pulses, synchronized with said received multilevel digits, h. means responsive to said level-representing signals and said timing pulses for generating a block synchronizing pulse in timed relationship with a specific digit in each of said received blocks, i. logic means responsive to said block sync pulses and said level-representing signals for generating a polarity inversion control signal when said specific digit of a code has a polarity opposite to said first polarity, j. polarity inversion means responsive to said polarity inversion control signal generated by said logic means for converting n successive level-representing signals into polarity-controlled n level-representing signals which indicate like amplitude but opposite polarity, and responsive to the absence of said polarity inversion control signal for passing n successive level-representing signals from said generating means directly, without polarity indication change, to the output thereof, and k. multilevel-to-binary converters means for converting the outputs from said polarity inversion means into a corresponding group of (m X n) binary bits.