The phrase "Calls Completion on No Reply", abbreviated simply as CCNR, refers to a particular call connection feature. This feature allows a caller to receive an automatic signal when a called party, who has previously not taken a call from them, may be available to take a call again. It can be activated during a call by executing a certain keyboard command when you hear the recipient’s phone ringing but don’t get an answer.

If CCNR is enabled, the system automatically detects when the person who has been called next hangs up their receiver and indicates this with a call to the caller. The caller then takes this call by lifting the handset and the system attempts to make a connection between the two participants. Only if the called party answers the call is this connection made.

The advantage of CCNR is that the caller is automatically informed by the system when a subscriber becomes available again and is able to receive calls. This may happen, for example, when the called person comes back to their office after a long absence and makes their first phone call again. This option means that the caller does not have to repeatedly make calls to reach the other person. CCNR is a feature that can only be used internally within a system. It can be provided for the entire system or only for individual participants.