Communication system using binary to multi-level and multi-level to binary coded pulse conversion

Claim 1

In a communication system including a transmitting end and a receiving end between which signals in the form of multi-level pulse words are transmitted through a communication circuit, said system comprising at said transmitting end first converter means for converting n-bit binary words into multi-level pulse words and at said receiving end second converter means for converting multi-level pulse words into n-bit binary words, the arrangement in which said first converter means comprises means for adding to each n-bit word and in a predetermined weight postion therein an additional bit having a predetermined value so as to obtain a modified (n+1) bit word, means for decomposing each such (n+1) bit word into a number k of partial binary coded words each having q (n+1)/k bits, means for deriving from each of said partial q-bit words the binary weighted sum of its q bits by adding the products of the binary values of a given polarity of said q bits by powers of two respectively equal to the binary weights of said q bits, means for deriving from said weighted sum a reduced sum having either of two possible polarities by substracting from said weighted sum one half of its maximum possible value, addition means for adding all of said reduced sums derived from the k partial words pertaining to the same (n+1) bit binary word for obtaining a resultant sum, means for determining the algebraic sign of said resultant sum, means for determining at any instant the algebraic sign of the current sum of the amplitudes of all previously transmitted multi-level pulses and for comparing said sign with that of said resultant sum, and coder means translating each one of said partial words into a first multi-level pulse having a given polarity when said signs are different and into a second multi-level pulse of the opposite polarity when said signs are the same, said first and second multi-level pulses being respectively derived from said one of said partial words and from a complementary word derived therefrom by substituting therein one bits for zero bits and zero bits for one bits, and in which said second coverter means at said receiving end comprises means for storing said additional bit and decoder means translating multi-level pulses into a partial binary coded pulse word for a given one of the two possible values of said additional bit and into the complementary partial binary coded pulse word when said additional bit has the other one of said two possible values.