Different types of telecommunications networks are known to the art. The typical telephone network offers telephony services. The telex network offers the telex communications service. A circuit switched data network offers data communications services, the paging network offers the paging service. The typical telecommunications network can be used as a carrier for other services, such as telex and data transmission, for instance. The packet switched network may be a carrier of different services, such as Datapack, Teletex, Videotex and Datel. Traffic in one network can be adapted for communication to destinations in another network, by introducing gateways or ports in the first-mentioned network. ISDN (Integrated Services Digital Network) is an integrated service network which is able to offer several of the aforesaid services. The subscribers connect all of their equipment to the same "wire pair" in ISDN.
A user will traditionally use different equipment, herein-after called terminals, and different procedures to obtain access to different networks. The function of the terminal is to make the services of the network available to the user. A given terminal has the functionality for interaction with a given network, the functionality for interaction with a user, and the functionality of coordinating the behaviour of the terminal to the user and the behavior of the terminal to the network. User interaction with the terminal is different and will depend on the network to which the terminal has access. This means that the user must be aware of the access procedure for each of those networks with which he wishes to communicate through his different terminals. This means in practice that one access procedure is used when telephoning, that another access procedure is used when using a mobile telephone, and that a third access procedure is used when wishing to page a subscriber. The supplementary services of a telephone network can be utilized by dialling or keying a specific key sequence. The same supplementary service, for instance unconditional call forwarding or conditional call forwarding, have different key sequences in different networks.
A common feature of all telecommunications networks is that they enable a connection to be established between two subscribers. Different networks are able to set up a connection between two terminals in the different networks, even when one network A cooperates with another network B through a port. On the other hand, none of the telecommunications networks is aware of why the connection is established between two terminals. Such knowledge lies beyond the makeup of the networks. Thus, if a subscriber X wishes to communicate with a subscriber Y and subscriber Y is located in a third network C which is different from A and B, none of the networks A or B is able to initiate the setup of a connection to subscriber Y in the network C.
A user Y who can be accessed in several different networks has a number of possibilities from which to choose in present-day techniques. Most typically the user Y does nothing, implying that a calling party X will have to search the called subscriber Y by making a number of calls in each of those networks that subscriber Y believes that subscriber X can be found. Another possibility for the user Y is to control incoming traffic to his/her/its present destination, by activating some form of redirection or diversion in one or in a number of the networks. In the following redirection and diversion are used as synonymous terms.