There is disclosed a method of digital signal transmission in which, for serially transmitting digital data of N channels, where N may for example be 16, 24 or 32, these data are serially and successively transmitted in groups of M, where M may for example be 2, 3 or 4, with each said group including data of K channels, where K may for example be 8, and in which a preamble with a pattern violating the rule of modulation for data transmission is provided, for example, at the foremost part of each such group, a data validity evaluation bit is added to the data of each such channel, and parity data is also provided to the totality of bits of each such group. A group address may also be provided to each such group for indicating its group number within the M groups.