In a digital telecommunications system having data packages carrying identification data, the identification data is characterized in that it is unique to the package within a station and does not depend on the identity of the originating station. The fixation system comprises an interference screw comprising a body having a distal end and a proximal end, screw threads extending longitudinally along the body, and a transversely-extending region formed in the body for receiving a transverse pin therein, whereby to securely lock the interference screw, and hence the graft ligament, to the bone. Then, in sequence the scan chains within said first aggregation of scan chains are reconfigured, then the scan chains within said second aggregation of scan chains are reconfigured, and finally the scan chains within said third aggregation of scan chains are reconfigured.