call forwarding if busy (ISDN) (CFB)

Call if Forwarding Busy (CFB) is a feature ofdigital communications networks that activates call forwarding( CF) in the event of a busy call. In the busy case, the local exchange transfers the incoming call to a specified number. The CFB function can refer to specific calls and services.

Since call forward ing is performed in the exchanges, it also takes place when the call number is suppressed, Calling Line Identification Restriction( CLIR). Call forwarding in the event of busy is described in ITU-T Recommendation I.252, Supplementary services for call termination.