---

• CCITT Rec. V.28 (11/1988) – ELECTRICAL CHARACTERISTICS FOR UNBALANCED DOUBLE-CURRENT INTERCHANGE CIRCUITS
• 1 Scope
• 2 Interchange equivalent circuit
• 3 Load
• 4 Generator
• 5 Significant levels (V1)
• 6 Signal characteristics
• 7 Detection of generator power-off or circuit failure