This part of IEC 62580 specifies the general architecture of the On-board Multimedia and Telematic Subsystem, which includes four categories of multimedia and telematic subsystems identified as: A Video surveillance/CCTV B Driver and crew orientated services C Passenger orientated services D Train operator and maintainer orientated services This part establishes: • the boundary between the OMTS and the on-board communication system, as described by the IEC 61375 series • the methodology to describe an OMTS in terms of abstract model • the general principles and the basic requirements to specify the services provided/needed by each category • the approach to ensure interoperability between services This part gives guidelines for: • OMTS classification • functional breakdown structuring • system breakdown structuring • formal specification of an OMTS This part is applicable to any type of train, e.g. open trains, multiple unit trains and closed trains. NOTE The general architecture provides a common basis for the application categories defined in part 2 and possible future parts of this series of standards. Consequently, the approach is homogeneous for all multimedia and telematic subsystems addressed by this series of standards.