Recommendation ITU-T Z.165 provides the specification of the runtime interface for TTCN-3 (Testing and Test Control Notation 3) test system implementations. The TTCN-3 Runtime Interface provides the recommended adaptation for timing and communication of a test system to a particular processing platform and the system under test, respectively. This Recommendation defines the interface as a set of operations independent of target language. The interface is defined to be compatible with Recommendation ITU T Z.161. This Recommendation uses the CORBA Interface Definition Language (IDL) to specify the TRI completely. Clauses 6, 7 and 8 of [ETSI ES 201 873-5 V4.6.1] specify language mappings of the abstract specification to the target languages Java and ANSI-C. A summary of the IDL-based interface specification is provided in Appendix A of [ETSI ES 201 873-5 V4.6.1]. This revision of the Recommendation contains amendments, clarifications, corrigenda and editorial corrections.