Abstract: Parallel data transmission system in which the data signals are converted to multilevel digital signals and transmitted through the channels of a frequency division multiplex system. To compensate for the delays between the data signals received in the various channels of the multiplex, a pilot signal is transmitted in each channel in the form of a signal which only has a real component. At the receiver side a filter circuit is used which comprises a first fixed coefficient part at whose input the data signal is multiplied by a component of the received pilot signal and a second part having two variable coefficients which are derived from the two components of the received pilot signal.

Abstract: An arrangement for digitally processing a given number of analog channel signals, more particularly a digital multiplexer and demultiplexer provided with a number of signal paths each comprising a recursive digital filter and delay circuits arranged in cascade therewith, said filter circuits having an amplitude-frequency characteristic of a lowpass filter having a cut-off frequency which is equal to half the bandwidth of a channel signal and a phase-frequency characteristic which is such that the difference between such a phase-frequency characteristic and the phase-frequency characteristic of a reference digital filter has a sawtooth-shaped variation, the slope of the sawtooth being opposite to the slope of the cooperating delay circuit. The arrangement furthermore comprises in cascade a discrete Fourier transformer connected to the signal paths.