Abstract: A time-locking method for stations which form part of a local star network in a multiplex data transmission system in which the exchanges between stations are organized in a single frame permitting the simultaneous writing and reading by way of transmission modules which are connected to the network via a coupler. The method has a first phase during which the forward/return propagation time is measured between each station and the coupler, a second phase during which the stations are synchronized with the master station, and a third phase duration in which the time position of each station is fixed in a time slot reserved for the locking of this station in the multiplex.

Abstract: Method of scrambling television pictures for which the video signals of each scanning line are of the M.A.C. type, that is to say time-division multiplexing of the analog chrominance and luminance components, characterized in that on transmission the components are each divided, in each line, one after the other, into two consecutive signals C and D, on the one hand, and F and G, on the other hand, the first signal C and F of which are then delayed for the duration of the second signal, and the second signals D and G are advanced for the duration of the first signals, the reference periods B and E which precede these respective components being excluded from this processing operation, the positions of the dividing points being derived from pseudo-random digital sequences, and the processing operation being intended to be applied on reception in the opposite sense for the simultaneous recovery of the luminance signal Y and the color difference signals U and V.

Abstract: An arrangement for deciphering and decoding television pictures which were scrambled at transmission by submitting the video signals to cyclic permutations from the addresses x.sub.i of points of cut produced by a pseudo-random digital address generator. Said video signals being separate components such as analog components of the MAC type, the arrangement comprises for recreating the permuted signals two sets of random access memories (Y.sub.1, Y.sub.2) and (C.sub.1, C.sub.2, C.sub.3, C.sub.

Abstract: A pseudo-random binary address generator is described which is designed for supplying addresses of cutting points of video signals for the purpose of encoding these signals by rotation of the two segments situated on either side of each cutting point, comprising three feedback registers (A), (B), (C) whose generating polynomials are irreducible and primitive, and in which the numbers of cells are different. These registers comprise several outputs a.sub.i b.sub.j c.sub.k, and the addresses of the cutting points are sums of N terms of weight 2.sup.O to 2.sup.N-1 and of coefficients S.sub.O to S.sub.N-1 of which at least a certain number are deduced from logic equations combining the outputs a.sub.i b.sub.j c.sub.k.

Abstract: A method for use in a local loop network comprising a plurality of stations which are distributed along a bus, each station being connected to the bus via a coupler which is inserted in the bus. The time-locking method for these stations comprises a transmission phase during which a looping unit which is also inserted in the bus transmits a frame (transmission frame) which consists of a synchronization word and one or more slots which initially do not contain data and which correspond to the time position occupied by each of the stations, a receiving phase during which the demodulation of the transmission frame by the master clock of the looping unit is performed after the retransmission in the form of a frame which is referred to as the receiving frame, of this frame to the coupler of each of the successive stations and, after the receiving phase, new transmission and receiving phases until the insertion of the data on the bus by each station during a transmission phase takes place with the desired accuracy.