What is CFB (Call Forwarding Busy)?

In case the called subscriber is busy, Call Forwarding Busy assistance redirects incoming calls, while CFNR redirects incoming calls when the incoming call is not replied to. Call Forwarding–Busy (CFB) grants a called person to have the system transmit message box or incoming calls addressed to the called subscriber’s public identity to another public
identity when the person is considered to be busy. CFB does not affect a subscriber’s ability to make calls. A subscriber may choose a forward-to-identity when the subscriber enrolls in the CFB.