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• Rec. ITU-T F.721 (1988) – Basic narrow band videophone service in the ISDN
• 1 Introduction
  • 1.1 Scope
  • 1.2 Bearer capabilities
• 2 Description of videophone service supported in the ISDN
  • 2.1 Definition
  • 2.2 Service description
  • 2.3 Applications of the videophone service
  • 2.4 Necessary quality characteristics
• 3 Intercommunication
  • 3.1 Intercommunication with telephony
  • 3.2 Intercommunication between different videophone services
  • 3.3 Intercommunication with other audiovisual and audiographic services
• 4 Service operation
  • 4.1 Call set-up
  • 4.2 Call release
  • 4.3 Change of service
  • 4.4 Addressing of terminals
• 5 Controls and indications
  • 5.1 User guidance
  • 5.2 Additional items
• 6 Supplementary services