Telephonic communications – Plural exchange network or interconnection – Multi-pbx interconnection
Reexamination Certificate
2001-03-30
2004-11-09
Deane, Jr., William J. (Department: 2642)
Telephonic communications
Plural exchange network or interconnection
Multi-pbx interconnection
C379S221010, C379S219000, C379S220010
Reexamination Certificate
active
06816588
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for switching telephone calls from a terminal in a first telephone network to a terminal in a second telephone network.
2. Description of the Prior Art
Private branch exchange systems at different locations within an organization are frequently connected to one another via dedicated lines to form a private network, which forms a first telephone network. This makes it possible for the subscribers to make telephone calls, for example, to one another within the private network without any need to pay charges for an individual call to an operator of a second, preferably public, telephone network.
Private networks allow the costs for exchange calls, that is to say telephone connections from terminals in the private network to terminals in a public telephone network, to be reduced. One service feature for reducing the costs of exchange calls from private networks is also referred to as “Least Cost Routing”, or LCR for short. In this case, many of the connections to terminals in the public telephone network can be transmitted via the private network. In addition, the exit to the public telephone network takes place only in the immediate vicinity of a local network to which a called terminal is connected. A further possibility for reducing costs for exchange calls is to dial a network provider who offers good tariffs for call switching.
The international Laid-Open Specification WO 98/08335 A discloses a separate connection control unit for connection of telephone terminals, in which a connecting route to a dialed subscriber, and a suitable network operator, are selected on the basis of cost-optimized connection data, which is calculated from a likewise disclosed data server based on geographic, statistical and tariff data, and is transmitted to a database in the connection control unit.
The International Laid-Open Specification WO 96/33583 A discloses a least cost router, which is connected to the outputs of a private branch exchange system in a private communications network and, in the event of a connection request within the private communications network, passes this connection request back to a specific input of the private branch exchange system.
The International Laid-Open Specification WO 97/39592 A discloses a communications system having a large number of connected private branch exchange systems, which each contain memory devices for holding connection data, together with implementation units, in order to set up an optimum connecting route via private branch exchange systems in the private communications system and/or switching centers in the public communications systems.
The International Laid-Open Specification WO 94/13109 A discloses a communications system having a large number of through-switching devices, in which case the communications system selects a different connecting path depending on the telephone number dialed by a terminal connected to it. The through-switching devices are each arranged in different tariff zones, so that a connection can be selected on the basis of the level of the charges by a network operator.
The service feature LCR is offered by private networks in which all the private branch exchange systems support this service feature. As such upgrading a private network by adding the service feature LCR, in the prior art, requires either the use of additional hardware devices, extensive changes to programs in each private branch exchange system in the private network, or replacement of all the private branch exchange systems which do not support this service feature by private branch exchange systems which do support this service feature. However, known solutions are highly complex, and are thus associated with major costs.
An object of the present invention therefore is to provide a method for switching telephone calls between different telephone networks using the LCR method and at low cost.
SUMMARY OF THE INVENTION
Accordingly, the present invention is based on the idea that the service feature of least cost routing (LCR) can be provided in a first telephone network which contains a number of private branch exchange systems by first of all passing all the connection requests from terminals in the first telephone network to terminals in a second telephone network to a central controller. As soon as the telephone number of a called terminal in the second telephone network is dialed by a calling terminal in the first telephone network, a telephone connection is set up to the central controller. The telephone number is then transmitted to the central controller. The central controller uses the local area code of the dialed telephone number to determine a private branch exchange system from which the transfer to the second telephone network will take place. A telephone connection is then set up to the private branch exchange system which has been determined.
The central controller has a directory, for example in the form of a file, which contains criteria which are taken into account when defining the private branch exchange system from which the first telephone network will be left. As already explained, the local area code is used to determine a private branch exchange system in the immediate vicinity of the destination. A further criterion may be the time of the connection request if particularly good tariffs are offered by different network providers at specific times of day or on specific days of the week.
New or amended tariffs from network providers can be taken into account particularly easily with the method according to the present invention, since only the directory in the central controller is adapted in the event of tariff changes. In telephone networks in which the service feature LCR is supported by all the private branch exchange systems, tariff changes, on the other hand, require adaptations in all the private branch exchange systems.
The present invention allows the service feature LCR to be offered in telephone networks in which the service feature LCR is supported only by the central controller. Private branch exchange systems in telephone networks which do not support this service feature are adapted such that they pass connection requests to subscribers in a second telephone network to the central controller rather than directly to the second telephone network. This adaptation can be carried out with little complexity in the private branch exchange systems. Particularly in telephone networks having relatively old private branch exchange systems, the method according to the present invention avoids the relatively old private branch exchange systems having to be replaced by new private branch exchange systems.
The first telephone network may be, for example, a private network of an organization. As mentioned initially, the private branch exchange systems are typically located at different sites in the organization, and are connected to one another via tielines. The second telephone network may be, for example, a public telephone network, which is operated by a network operator.
In one preferred embodiment, each private branch exchange system is configured such that it sets up a connection to the central controller immediately after an exchange code character has been dialed. The other characters in the telephone number are transmitted to the central controller once they have been dialed by the subscriber. The central controller starts to evaluate the character sequence of the telephone number as soon as the last character has been dialed and transmitted. The time which a subscriber needs to dial the entire character sequence is considerably longer than the time which is required to set up the connection to the central controller and to evaluate the character sequence. The setting up of the connection to the called terminal is thus delayed only slightly.
The method is also suitable for private networks in which the private branch exchange systems have associated code characters. These code numbers are used, for example in conjunction w
Bell Boyd & Lloyd LLC
Deane, Jr. William J.
Siemens Aktiengesellschaft
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