This document presents a consolidation of performance requirements from two sources: RTCA /DO-144 dated March 12@ 1970 and Change 1 to DO-144@ posted as RTCA Paper No. 232-70/EC-643@ dated November 5@ 1970; and the performance standards referred to in paragraph (a)(1) of Federal Aviation Administration (FAA) Technical Standard Order (TSO)-C47c@ dated February 20@ 1973. The document includes the technical changes/advances necessary to ensure proper operation with Mode S and TCAS interrogators. The document is a coordinated effort with EUROCAE WG-49.