Abstract: Television system using a marking code superimposed on a picture.According to the invention, this code is constituted by a strip located in the right-hand part of the picture and formed by a periodic sequence of white and black areas constituting a clock and by a strip located in the left-hand part of the picture and formed by a sequence of white or black areas constituting the actual code. A decoder detects the presence of clock signals and compares the code received with stored codes.

Abstract: 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 receivin

Abstract: A system for transmitting information between an emitting center and receiving stations, comprising: a subscription administration center generating a plurality of subscriber's keys C.sub.i changing randomly at relatively long intervals of the order of a month; in the emitting center: a generator of an operating key K changing randomly at relatively short intervals of the order of a few minutes; a circuit for forming messages M.sub.i obtained from said subscriber's keys C.sub.i and from the operating key K by means of an algorithm, all the messages M.sub.i then being directed towards the emitting center; and automatic encryption means using the operating key K, in each receiving station: a subscription holder on which is recorded a signal corresponding to at least one of the subscriber's keys C.sub.i ; a circuit for restoring the operating key receiving the messages M.sub.i and the subscriber's key C.sub.

Abstract: An arrangement for the electrical control of the keyboard of a video or audio tape recorder includes electromechanical levers acting on the usual rod system associated with the keyboard in substitution of the conventional keys. The levers are essentially bellcranks and are associated with tumblers and electromagnets.