Sch 3 para 2 Description of the subsystems
For each subsystem or part of a subsystem, the list of constituents and aspects relating to interoperability is proposed by the Secretary of State at the time of drawing up the relevant draft NTSN. Without prejudging the choice of aspects and constituents relating to interoperability or the order in which they will be made subject to NTSNs, the subsystems include the following—