| 摘要 |
A text video-transmission system comprising an information emitting center and receiving stations, the emitting center comprising encryption means using an operating key, each receiving station comprising decryption means using the operating key, wherein in this system, the encryption means of the emitting center comprise: a generator delivering a numerical signal representing an operating key K, this key changing randomly at predetermined intervals; an automatic encryption means comprising: a discriminator with an input connected to a magazine memorizing circuit from which it receives clear octets, this discriminator being capable of distinguishing, among these clear octets, those wherein the 7th and 6th binary elements are zero, an OR-exclusive logic circuit connected to the discriminator from which it receives octets wherein the 6th and/or 7th binary elements are not zero, this logic circuit having an output which carries encrypted octets; a generator of encoding octets, the decoding means of each receiving station comprising: a generator of a numerical signal representing the operating key K in use in the emitting center, automatic decryption means comprising: a discriminator adapted to distinguish, among the encrypted octets, those wherein the 7th and 6th binary elements are zero, an OR-exclusive logic circuit connected to the discriminator; and a generator for decoding octets.
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