Communication system

Claim 1

A communication system such as video-text, teletext etc., for transmitting message data having at least one input-output station, at least one external computer, and a transmission line, connecting said input-output station to the external computer, a computer exchange station coupled to said transmission line between said external computer and said input-output station, for transmitting digitally coded data in both directions, whereby the data are prepared according to the ISO-layer model, reference model according to DIS 7498, and whereby the digitally coded data comprise data specifically relating to the system and user-related data, or data related to individuals, or other sensitive data for a videotext system, whereby the input station comprises a plurality of ISO data preparation layers, a selectively connectable coding and decoding module to encrypt and decrypt respectively of the bypass-type disposed between the third layer and the active layer of the layer model, said active layer being disposed on top of said third layer, and a switching device disposed within said coding and decoding module for effectively connecting said coding and decoding module to said ISO data preparation layer at least during the transmission of the message data, and wherein the message related data are coded whereas the data specifically relating to the system remains uncoded, and a coded card including the source code for said coding and decoding module and insertable therein for activating said switch-in device.

Claim 5

A method for transmitting message-related digitally coded data in a communication system such as videotext, teletext etc., with at least one input-output station and at least one external computer, the station and the computer being connected to each other via a transmission line, and interconnected to a computer exchange station or postal service computer for transmitting the digitally coded data, whereby the data are prepared according to the ISO-layer model (reference model according to DIN ISO 7498), in particular a method of data preparation in the videotext system, comprising the step of: coding to encrypt the digitally coded data during the course of data preparation, said coding taking place between the third layer and the active layer of said layer model, said active layer being disposed on top of said third layer.

Claim 6

A method for transmitting message-related digitally coded data in a communication system such as videotext, teletext etc., with at least one input-output station and at least one external computer, the station and the computer being connected to each other via a transmission line, and interconnected to a computer exchange station or postal service computer for transmitting the digitally coded data, whereby the data are prepared according to the ISO-layer model (reference model according to DIN ISO 7498), in particular a method of data preparation in the videotext system, comprising the step of: coding to encrypt the digitally coded data during the course of data preparation, said coding taking place between the third layer and the active layer of said layer model, said active layer being disposed on top of said third layer.