FEATURES GUIDE

General Features
Features Guide 79
Completion of Calls to Busy Subscriber (CCBS)
Description
Allows the extension users to set the telephone to receive callback ringing when a busy called
party on an ISDN line becomes free. A special dial tone informs the caller that the called party
is busy. When the caller answers the callback ringing, other party's number is automatically
dialled.
This feature is one of ISDN's services and its availability depends on the service of your
telephone company. This feature is in accordance with the ETS 300 359. (ETS: European
Telecommunication Standard)
Conditions
• This feature is enabled or disabled by System Programming.
• An extension can set only one CCBS at a time.
• A digital proprietary telephone (DPT) and single line telephone (SLT) can set the CCBS to
a busy party.
• The CCBS that has been set by an outside party works only if the called busy extension is
a DPT or SLT and the call arrives via Intelligent Call Handling 1:1.
• If the callback ringing is not answered in 4 rings (within 10 seconds) the callback is
cancelled.
• The callback rings even if the extension has set the Call Forwarding or Do Not Disturb
(DND).
• The caller can use the telephone before the callback rings. The setting is cancelled only in
the following conditions.
— By the cancelling operation.
— If there is no callback ringing within 60 minutes.
— If the system power is off./If you reset the system.
• This feature does not work if the extension has set Data Line Security.
• The time the system waits before sending a CCBS signal while hearing a special dial tone
is programmable.
Programming Guide References
• [100] Flexible Numbering
• [143] CCBS Feature
• [990] System Additional Information
Features Guide References
• Dial Tone, Distinctive
User Manual References
• 2.2.4 When the Dialled Line is Busy or There is No Answer