This part of IEC 61993 specifies the performance requirements, technical characteristics, operational requirements, methods of testing and required test results for shipborne automatic transponder system installations using VHF digital selective calling (DSC) techniques and is associated with IEC 60945. When a requirement in this standard is different from IEC 60945, the requirement in this standard shall take precedence. The shipborne transponder installation is intended to assist in the efficient operation of shipreporting systems and vessel traffic services (VTS) by enabling operators to identify, poll and automatically locate and track ships when they are approaching, entering and sailing within the limits of a ship-reporting system. The system may also be used for the identification of ships by a ship and ships by aircraft. A description of the system is given in annex C. This standard – incorporates the technical characteristics included in ITU-R Recommendation M.825 for transponder systems using DSC and the technical characteristics included in ITU-R Recommendation M.489 for VHF radiotelephone equipment; – incorporates the technical characteristics of DSC equipment and the operational procedures for its use contained in Recommendations ITU-R M.493 and ITU-R M.541; – incorporates applicable parts of the performance standards of IMO Resolution A.803 for shipborne VHF radio installations; – takes account of IMO Resolution A.694 for general requirements; and – conforms with the International Telecommunication Union (ITU) Radio Regulations where applicable. This standard for a transponder system is not intended to meet the requirements for a universal automatic identification system (AIS), as detailed in IMO Resolution MSC.74(69) annex 3. NOTE All text in this standard whose meaning complies with that in the normative references, namely IMO Resolution A.803(19) and ITU-R Recommendations M.825, M.489, M.493 and M.541 is followed by a reference to the source (number of IMO Resolution or ITU-R Recommendation and paragraph number) in brackets.