Communication system for detecting an unauthorized intruder term

Details Communication system for detecting an unauthorized intruder term Communication system for detecting an unauthorized intruder term

1996-11-12

1999-07-20

Loomis, Paul

Telephonic communications

With usage measurement

Call charge metering or monitoring

379 7, 379 27, 379188, 379399, 379412, H04M 1500

Patent

active

059265299

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention relates to a communication system comprising a station for charge metering of a connection point and to terminal units connected to connection points coupled to the station.
In many communication systems it is often not guaranteed that only the authorized subscriber can communicate with other subscribers via his terminal unit. It is possible, for example, that unauthorized connection lines between a terminal unit of the authorized subscriber and the station, which forms, for example, part of a telephone exchange, are manipulated. This damages both the subscriber and the operating company of the network.


SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a communication system of the type defined in the opening paragraph in which possibilities of manipulation by unauthorized persons are largely avoided.
The object is achieved by a communication system which has the following characteristic features: connection point, which station comprises a monitoring circuit for or evaluating the contents of a message that has arrived from the connection point after the request for a connection set-up has arrived, and connection point are established.
The communication system according to the invention comprises in the station which is provided for charge metering of, for example, a call, an additional monitoring circuit assigned to a connection point. The monitoring circuit picks up a request for a connection set-up which is generally sent by an authorized subscriber's terminal unit connected to a connection point. The authorized subscriber's terminal unit may, for example, send a specific message to be analyzed by the monitoring circuit after the request for a connection set-up, so that the monitoring circuit can recognize the authorization. If, after a given period of time after a request for a connection set-up, the monitoring circuit has still not received any message from the terminal unit connected to the connection point, a request for a connection set-up must have been received from a terminal unit of an unauthorized subscriber. If no message from the connection point, or an erroneous message is available, the monitoring circuit establishes an invalid parameter of the connection point and a rejection of the request for a connection set-up follows.
The exchange of specific agreed messages between a connection point and the monitoring circuit, and the check thereof provides that both the authorization of a subscriber terminal is verified and an unauthorized connection set-up is prevented in a simple manner.
The intrusion of an unauthorized terminal unit at the connection point can be prevented if a terminal unit connected to a connection point is assigned an evaluation circuit which sends out an error message to the monitoring circuit after the intrusion has been detected. The monitoring circuit designates the error message as an invalid parameter. The monitoring circuit receives a message from the evaluation circuit that an unauthorized subscriber has intruded while the terminal unit is in the state of rest. Once the message has been received, no connection is set up.
In a further embodiment of the invention, a terminal unit connected to a connection point is assigned an evaluation circuit which comprises a first counter for counting the charge metering signals and a first controller for forming a message which contains a first count of the first counter for the monitoring circuit, and the monitoring circuit comprises a second counter for counting the charge metering signals and a second controller for evaluating the message received from the evaluation circuit and for designating the count of the first counter as an invalid parameter if the counts of the two counters are not the same.
A terminal unit is assigned an evaluation circuit which counts the charge metering signals by a first counter. A second counter in the monitoring circuit also counts these signals. Before the connection is set up, the monitoring circuit is informed of the cou

REFERENCES:
patent: 4760592 (1988-07-01), Hensley
patent: 4885768 (1989-12-01), Genin
patent: 5086459 (1992-02-01), Perry
patent: 5099515 (1992-03-01), Kobayashi et al.
patent: 5436959 (1995-07-01), Dake et al.
patent: 5559874 (1996-09-01), Panosh

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