This ETS defines: a) an identification plan for mobile subscribers in the GSM system; b) principles of assigning telephone and ISDN numbers to mobile stations in the country of registration of the mobile station; c) principles of assigning mobile station roaming numbers to visiting mobile stations; d) an identification plan for location areas and base stations in the GSM system; e) an identification plan for MSCs and location registers in the GSM system; f) principles of assigning international mobile equipment identities; g) principles of assigning zones for regional subscription. h) an identification plan for groups of subscribers to the Voice Group Call Service (VGCS) and to the Voice Broadcast Service (VBS); and identification plan for voice group calls and voice broadcast calls; an identification plan for group call areas.