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• CCITT Rec. I.431 (11/1988) – PRIMARY RATE USER-NETWORK INTERFACE – LAYER 1 SPECIFICATION
• 1 Introduction
  • 1.1 Scope and field of application
• 2 Type of configuration
  • 2.1 Point-to-point
  • 2.2 Location of interfaces
• 3 Functional characteristics
  • 3.1 Summary of functions (Layer 1) (see Figure 2/I.431)
  • 3.2 Interchange circuits
  • 3.3 Activation/deactivation
  • 3.4 Operational functions
• 4 Interface at 1544 kbit/s
  • 4.1 Electrical characteristics
  • 4.2 Frame structure
  • 4.3 Timing considerations
  • 4.4 Time slot assignment
  • 4.5 Jitter
  • 4.6 Interface procedures
  • 4.7 Maintenance
• 5 Interface at 2048 kbit/s
  • 5.1 Electrical characteristics
  • 5.2 Frame structure
  • 5.3 Timing considerations
  • 5.4 Jitter
  • 5.5 Tolerable longitudinal voltage
  • 5.6 Output signal balance
  • 5.7 Impedance towards ground
  • 5.8 Interface procedures
  • 5.9 Maintenance at the interface
  • 8.1 Provision of power
• 6 Connector
• 7 Interface wiring
• 8 Power feeding
  • 8.1 Provision of power
  • 8.2 Power available at the NT
  • 8.3 Feeding voltage
  • 8.4 Safety requirements
• ANNEX A – Time slot assignment for interfaces having only Ho-channels
  • A.1 1544 kbit/s interface
  • A.2 2048 kbit/s interface
• ANNEX B – Time slot assignment for 2048 kbit/s interfaces having an H11-channel
• APPENDIX I – Pulse mask for interface at 1544 kbit/s