Differential pulse code modulation system with neutralization of direct current information

Differential pulse code modulation system, wherein an analog signal is converted into binary digital words of a constant length and the digital words are fed through a recording or transmission channel with a high-pass characteristic, the band-width of the analog signal being limited to such an extent that the highest frequency of the analog signal is smaller than half of the sampling frequency which is used for the analog-digital conversion, comprising code converting means for providing digital words which pertain to the analog signal difference "Zero" and to a range of relatively small positive and negative signal differences adjacent to the signal difference "Zero", with the same number of "0" bits and "1" bits, while the digital words pertaining to the remaining signal differences in a given range of the analog signal include an unequal number of "0" bits and "1" bits, the order of minority bits in consecutive positive and negative digital words changing substantially linearly with the values of the remaining analog signal differences, and the positive and negative digital words having the same absolute value being complementary.