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TechSpec
  • Foreword
  • 0 Scope
  • 1 Framework for the description of telecommunication services
  • 2 Description of circuit telecommunication services by the attribute method
  • 3 Characterization of circuit telecommunication services
  • 4 Provision of telecommunication services
  • A.1 Information transfer attributes
  • A.2 Attributes describing the access at the user equipment
  • A.3 Interworking attribute
  • A.4 General attributes
  • B.1 High layer attributes
  • B.2 Low layer attribute (bearer capabilities)
  • B.3 General attributes
  • C.1 Scope
  • C.2 Network Determined User Busy (NDUB) condition
  • C.3 User Determined User Busy (UDUB) condition
  • C.4 Mobile subscriber busy
  • D.1 Scope
  • D.2 Mobile Originated Call Set-up
  • D.3 Mobile Terminated Call Set-up
  • F.1 General
  • F.2 Supervisory tones
  • F.3 Recorded announcements
  • F.4 Application of call control cause information elements to supervisory tones

C.4 Mobile subscriber busy

22.0013GPPPrinciples of circuit telecommunication services supported by a Public Land Mobile Network (PLMN)Release 17TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

A mobile subscriber is considered to be busy if either a "Network Determined User Busy" or a "User Determined User Busy" condition occurs.

Some supplementary services (e.g. Call Forwarding on Busy) may cause the call not to be cleared when a busy condition occurs.

Annex D (normative):
Call set-up procedures