automatic callback
Automatic callback is a telephone system feature that permits a caller who gets a busy signal to instruct the system to establish the connection when the line becomes available. The system does this by retaining both the called and calling numbers, redialing the called number periodically and alerting the caller when the connection has been made. Automatic callback can be a function of the terminal, the switching system or may be shared between the two. Automatic callback and a related technology called click-to-callback are frequently used in call centers.