A device for transmission of digital signals between two units movable relative to each other, particularly with non-contacting rotating data transmission devices, comprises an encoder on a transmitter side along a signal path for conforming a coding of the digital signals to transmission characteristic of a transmission path, so that a given spectral distribution of signals is attained. An optional decoder on a receiver side restores original signals, so that the coding remains concealed, but a substantially more reliable transmission is achieved.