Patent ID: 6882719

Claim:
A method for making an outgoing call reservation in an exchange system, comprising the steps of: (a) determining whether there is an input of the outgoing call reservation request from a subscriber of the exchange system, when a specified called party is in a busy state; (b) if the outgoing call reservation request is input from the subscriber, making a re-dialing to a telephone number of the specified called party repeatedly by a predetermined times of retries, concurrently using a plurality of idle central office lines assigned to a redial sub-group, until a connection to the called party is successfully established via one of the central office lines of said redial sub-group; and (c) if there is any central office line of the redial sub-group connected to the called party according to the re-dialing on the outgoing call, connecting the corresponding central office line to the subscriber of the exchange system to establish a speech channel.