Abstract: Transmission system of frequency division multiplex signals on a digital link. At the transmitting end of the digital line, the frequency division multiplex signals are sampled and coded into n-bit sample words. These sample words are transcoded into p-bit on-line words with p smaller than n through a transcoding procedure which makes a plurality k of successive levels of the n-bit code correspond to one and the same level of the p-bit code. The number k is selected depending on the maximal level reached by a sample word in a block of successive sample words. The number k is transmitted to the receiving end of the digital link by a control word for reverse transcoding of the on-line p-bit words into reconstituted n-bit sample words.