The present invention relates to a method and an arrangement related to synchronous switching, for example in relation to digital communication between devices being arranged on boards which are housed in racks having a back-plane associated therewith, and for the improvement of minimum delay and configuration flexibility, combined with high capacity and high reliability, it is according to the present invention suggested a decentralised concept, or a decentralised architecture, specifically comprising a novel so-called RSO-bus arranged in the back-plane of said rack.