2.1.1 Call states at the user side of the interface

The states which may exist on the user side of the user-network interface are defined in this sub clause.

2.1.1.1 Null state (U0)

2.1.1.2 Call initiated (U1)

2.1.1.3 Overlap sending (U2)

2.1.1.4 Outgoing call proceeding (U3)

2.1.1.5 Call delivered (U4)

2.1.1.6 Call present (U6)

2.1.1.7 Call received (U7)

2.1.1.8 Connect request (U8)

2.1.1.9 Incoming call proceeding (U9)

2.1.1.10 Active (U10)

2.1.1.11 Disconnect request (U11)

2.1.1.12 Disconnect indication (U12)

2.1.1.13 Suspend request (U15)

2.1.1.14 Resume request (U17)

2.1.1.15 Release request (U19)

2.1.1.16 Overlap receiving (U25)