A device is disclosed for encoding a stream of databits of a binary source signal (S) into a stream of databits of a binary channel signal (C) satisfying a (d,k) constraint, wherein the bitstream of the source signal is divided into n-bit source words (x1, x2), which device comprises converting means (CM) adapted to convert said source words into corresponding m-bit channel words (Y1, Y2, Y2). The converting means (CM) are further adapted to convert n-bit source words into corresponding m-bit channel words, such that the conversion for each n-bit source word is parity preserving (table I). The relations hold that m>n≧1, p≧1, and that p can vary. Preferably, m=n+1. Further, a sync word generator (9) is available for generating a q-bit sync word also satisfying said (d,k) constraint, the said sync word starting with a ‘0’ bit and ending with a ‘0’ bit, the device further comprising merging means (19) for merging said sync word in said stream of databits of the binary channel signal, and that q is an integer value larger than k. (FIG. 1) Further, a decoding device is disclosed for decoding the channel signal obtained by means of the encoding device.