If an incoming call can be associated with a user but not transferred, because no rule of the user’s Rule Book is applicable, the caller hears a busy signal. Internal callers also see the message "Subscriber not available" in the display.

If a user has no rules defined, and no Call Forwarding is set, it is attempted to connect the call to the original number for 60 seconds. If the destination does not answer the call, the caller hears a busy signal. Internal callers also see the message "Subscriber not available" in the display.

If a number cannot be assigned, i.e. neither to a user nor to a gateway connection (e.g. to a sub PBX), the call is rejected.