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• ITU-T Rec. Q.512 (1988)
• 1 General
• 2 Scope of Recommendation
• 3 Characteristics of digital exchange interfaces for subscriber access
  • 3.1 General
  • 3.2 Interface V1
  • 3.3 Interface V2
  • 3.4 Interface V3
  • 3.5 Interface V4
• 4 Characteristics of analogue exchange interface for subscriber access
  • 4.1 Interface Z
• 5 Combined digital and analogue interface for subscriber access