Companding pulse code modulation system

Claim 1

Compression coder for coding original samples of analog signals into PCM signals in which the amplitudes of the original samples to be coded are distributed into amplitude ranges forming the widths of quantizing steps which exponentially increase with amplitude and the amplitudes of the corresponding compressed samples being distributed into successive equal amplitude ranges forming the heights of said quantizing steps and defined by binary digit combination signals expressed in a PCM code, comprising a network of identical cascaded attenuators, each of said attenuators having a first state in which its attenuation is zero and a second state in which its attenuation is two, means for applying to the input of said network samples of said analog signals, a plurality of comparators respectively comparing to a predetermined voltage the signals at the outputs of the attenuators, a plurality of switching means respectively controlled by said comparators and selectively controlling the states of the attenuators, whereby the output signals of the comparators form binary digit combination signals representative of said samples expressed in a special code comprising a set of successive one digits and an adjacent set of successive zero digits in which the number of one digits is equal to the decimal number of the quantizing step and the number of zero digits is equal to the complement of said decimal number to the total number of said quantizing steps, the digits of the special code combination representative of an original sample being correlated to the digits of the PCM code combination representative of the corresponding compressed sample by linear relationships, and a computer deriving the digits of the PCM code combination representative of the compressed sample from the digits of the special code combination representative of the corresponding original sample.