Abstract: In order to protect audio signals against copying, it is proposed to mix the audio signal with at least one non-audible disturbance signal. A first disturbance signal may be a low-frequency signal which is added to the audio signal, while a second disturbance signal may be a high-frequency disturbance signal which is multiplied with the audio signal. Additionally, the second disturbance signal may be modulated by a modulating signal comprising either the original or inverted original signal, or spoken messages indicative of an illegal copy.

Abstract: A method and an apparatus for modifying video signals in such a manner that, when recording said signals with a tape recording apparatus, the control of this apparatus is disturbed, which signals comprise image point signals grouped according to image lines and preceded, in each line, by a line synchronization pulse and a colour synchronization signal, the plurality of lines being combined to a frame preceded by a frame synchronization pulse, the image point signals being situated at one side, and the synchronization pulses at the other side of a zero level, in which additional pulses resembling line synchronization pulses having a deviating shape or situated in deviating points of a frame are added. In particular, in at least a part of the frames, in a number of last lines the normal line synchronization pulses are removed in arbitrary locations, and, instead thereof, additional pulses with a deviating shape, and in particular a shorter duration, are introduced.

Abstract: A video camera system provides automatic intensity control and includes an imaging system and an image transducing apparatus having an entry window which is image line scanned and on which images of pictures to be taken are formed by the imaging system. The image transducing apparatus transforms these images into electrical output signals which are converted by an amplitude to frequency converter into control signals of corresponding frequency.