| 摘要 |
<p>In a communication system, such as the videotex system, the preparation of data is carried out according to the so-called ISO-layer model before sending the data through a conventional telephone line. Since telephone lines may be overheard, the danger exists that unauthorized persons acquire personal data. The invention provides between the third layer and the active layers situated on top of the ISO-strata model a coding and decoding element connectable as desired like a bypass, which at least during the transmission of the data themselves is effectively connected during the preparation of the data. Thus, the possibility is given to code safety related data before they are sent through the telephone line.</p> |
