On 20 September 2013, a loss of separation occurred between two en route Airbus A330s under radar surveillance in controlled airspace near Adelaide. The potential conflict was resolved with TCAS RA action by one of the aircraft involved but the TCAS equipment on board the other aircraft appeared to have malfunctioned and did not display any traffic information or generate an RA. The complex pattern of air routes in the vicinity of the event was identified by the Investigation as a Safety Issue requiring resolution by the ANSP and the response subsequently received was assessed as satisfactory.