Abstract: When an optional communications device connected to a public network is entered as an extension terminal accommodated by a private network, the communications device sends a predetermined special number. If the service control device provided in the public network receives the special number, then it prompts the communications device for the identification information of a user of the communications device. At the prompt, the user transmits the user identification information from the communications device to the service control device. If the identification information is preliminarily entered, then the communications device sends a user number in the number system of the public network assigned to the communications device to the service control device. The service control device enters the user number as being associated with a predetermined number in a number system in the private network.

Abstract: An incoming call controller for preferentially connecting a waiting calling subscriber, who had previously made more unsuccessful call attempts than any other waiting calling subscriber, to a called subscriber. The unsuccessful call attempts result in the calling subscriber receiving a busy signal. Call registering apparatus within the incoming call controller store identification data of each particular calling subscriber or calling terminal receiving a busy signal. After identification data is registered, the call register indicates future unsuccessful call attempts by incrementing a data field comprising the number of unsuccessful call attempts of the particular calling subscriber or calling terminal. A call manager within the incoming call controller identifies the calling subscriber registered as having previously made the most unsuccessful call attempts.