Abstract: The present invention relates to the read-out of a data carrier having a track along which there is transcribed an angularly modulated carrier wave. In accordance with the present invention, there is provided a system for processing the read-out signal, which uses a feedback loop correcting the duty factor of a restored rectangular waveform when its value deviates from the value 0.5.

Abstract: The present invention relates to methods for protecting against drop-outs in a sound signal recorded on a video-disc. It consists in recording onto a video-disc the same sound signal through the sub-carriers with a constant delay from one to the other. On reading out this video-disc, the two sub-carriers are restored to synchronism and the sub-carrier not altered is chosen for playing the sound signal.

Abstract: A coder designed to receive color television audio video signals where a carrier wave is frequency modulated by the luminance signal and a sub-carrier wave is modulated by time multiplexed chrominance signal and audio signal; the carrier and the sub-carrier waves are linearly mixed and the resultant signal is converted into a multiplex wave formed by a train of length modulated pulses; the sub-carrier frequency is higher than the highest frequency of the luminance signal and the lowest instantaneous frequency of the carrier minus the highest frequency of the luminance signal is at least equal to the sub-carrier frequency; the multiplex signal may be transmitted and registered on a data carrier; and a decoder adapted for cooperating with the coder, for decoding the multiplex signal coming from the transmission channel or the read out data carrier and delivering the audio video signals.

Abstract: The invention relates to a system optically recording information, by the insolation of a photosensitive layer deposited on a substrate, on a track of substantially constant width. The system comprises a device for controlling the energy emitted by the source in response to the non-uniformity of the reflexion coefficient of said surface, said control device being such that the energy actually transmitted to the photosensitive layer is constant when the modulation signal has the value 1.

Abstract: The invention relates to the multiplexed transmission of television audio-visual signals which comprise, for example, a luminance signal successive chrominance signals and at least one audio signal. The method in accordance with the invention utilises a subcarrier wave f, frequency modulated, on the one hand, by the chrominance signals, and on the other, by a train of isochronous pulses emitted during the line blanking intervals of the luminance signal and amplitude modulated by the audio-frequency signal. The multiplex signal which will subsequently be decoded, is obtained by frequency modulating a carrier wave by a signal which is the sum of the luminance signal Y and the above mentioned frequency modulated subcarrier.