Abstract: Apparatus for decreasing the d.c. component of digital signals derived from an analogue signal which may be a television video or audio signal, comprises analogue to digital converter means for producing digital words corresponding to samples of the analogue signal, a memory device for subjecting the words to a specific code conversion and circuitry for combining the coded words together in groups of two words with one of the words ones complemented and preferably partially interleaved with the other of the words of each group. The apparatus is applicable to use for both the recording of color T.V. video signals as well as for the transmission of such signals.