The Call Completion to Busy Subscriber (CCBS) feature is based on the existing auto callback and supplementary service - completion of calls (QSIG SS-CC) features. It provides the auto callback functionality to be used on calls to or from the public network. The server informs the caller as soon as the busy subscriber becomes available.
This feature supports the following:
ETSI-TSC (Temporary Signaling Connection) for incoming calls. In Communication Manager Release 5.0 and earlier releases, TSC is available for ETSI only for outgoing calls. TSC is currently available in both directions for QSIG.
ETSI-CCBS for incoming calls. In Communication Manager Release 5.0 and earlier releases, CCBS is only fully available for internal users and for users on systems interconnected by DCS, QSIG, or SIP trunks. On the ETSI interface, CCBS is supported for outgoing calls only. Starting with Communication Manager Release 5.1, CCBS on the ETSI interface is fully available in both directions (incoming and outgoing).
Restriction: ETSI-TSC and ETSI-CCBS are implemented without gateway functionality (ETSI - QSIG/DCS/SIP).
The supplementary service Completion of Calls has been added as new ETSI ISDN functionality. This feature is supported only in countries where the ETSI ISDN protocol is supported.
This feature must be supported by the service provider. Some service providers offer Call Completion without any additional charge, but you need to apply for it.
Completion of Calls is known as Auto callback at the user side.
