Abstract: A digital controller provides digital signals to audio modules; the digital signals include both clock signals and data. All of the logic circuits of the controller and of the modules are clocked on the receipt of a rising edge. However, to avoid interference from regular clock pulses, the clock pulses are altered to have a variable mark-space ratio which means that the clock pulses arrive at random times and have random widths and thus appear to be randomized. Use of randomized clock signals can avoid tones appearing in an audio system, and also avoids interference effects in other electrical systems. The use of randomized clock signals is particularly helpful when designing digital circuits which meet current regulations controlling electromagnetic emissions.

Abstract: An audio mixing console incorporates a number of audio modules connected in series, with the first module being serially connected to a digital controller. The digital controller provides digital signals to the audio modules, the digital signals comprising both clock signals and data. Data is sent by the controller to each audio module by way of a data coder which randomizes or scrambles the data stream such that it is not cyclic or repetitive. The coding circuit may be a maximal length pseudo number sequence generator, and this enables decoding to be made by a complementary decoding circuit without links between coder and decoder being required. As the data output appears completely random, it has no fundamental frequency and consequently there is no interference from crosstalk.