completion of call to busy subscriber (CCBS)

With the Completion of Call to Busy Subscriber (CCBS) feature, a connection is not automatically established when the destination line is busy until the busy status is cleared at the destination line.

However, automatic callback must have been activated by the caller on his terminal beforehand. If this requirement is met, the called party's exchange waits until the called party hangs up and signals this back to the calling party's exchange, which then picks up the connection.

Completion of Call to Busy Subscriber is described in Q.733.3 by the ITU-T. CCBS does not work on private branch exch anges and is limited to the network of a single carrier. This feature cannot be used across networks.