IEC 62580-1:2015 specifies the general architecture of the On-board Multimedia and Telematic Subsystem (OMTS), which includes four categories of multimedia and telematic subsystems identified as:- Video surveillance;CCTV,- driver and crew orientated services,- passenger orientated services and- 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.