Abstract: An apparatus displays a video signal (VID) by means of a scan (SCAN). The apparatus may be, for example, a television set. The apparatus comprises a device (SCAVEM) for modulating the scanning rate (Vscan) as a function of the derivative (DLUM) of a luminance signal (LUM) extracted from the video signal (VID). This enables the subjective display quality to be improved. The apparatus has the following characteristic feature in order to obtain an even better quality, notably when the apparatus is used for displaying video signals of different types. The derivative (DLUM) of the luminance signal, as a function of which the scanning rate (Vscan) is modulated, is obtained by means of a difterentiator circuit (DIFF) having a controllable frequency response (CFR).

Abstract: The invention relates to a device for displaying a video signal on a screen by means of a scanning operation, said video signal being characterized by an assembly of parameters, said display device comprising a derivative circuit for generating a derivative signal from said video signal, a threshold circuit for performing a threshold operation at a given threshold on said derivative signal so as to generate a modified derivative signal, a modulation circuit for modulating the scanning velocity on the basis of said modified derivative signal.

Abstract: An apparatus displays a video signal (VID) by means of a scan (SCAN). The apparatus may be, for example, a television set. The apparatus comprises a device (SCAVEM) for modulating the scanning rate (Vscan) as a function of a derivative (DLUM) of a luminance signal (LUM) extracted from the video signal (VID). This enables the subjective display quality to be improved. The apparatus has the following characteristic feature in order to obtain an even better quality, notably when the apparatus is used for displaying video signals of different types. The derivative (DLUM) of the luminance signal, as a function of which the scanning rate (Vscan) is modulated, is obtained by means of a differentiator circuit (DIFF) having a controllable frequency response (CFR).

Abstract: A video amplifier includes three amplifier circuits (TR, TG, TB) for the red, the green and the blue signals which are each provided with a different feedback signal which changes value when the signal exceeds a certain threshold, by a feedback resistor circuit having two cascade-arranged resistors (R4R in cascade with ?R1+R2+R3!), with their central junction being connected by a diode (Tth) to a fixed voltage (DZ). The ratio value between the two cascade-arranged resistors is different between the amplifier circuits, and moreover, a part (R1 or ?R1+R2!) of the resistor at the base of a cascade arrangement of resistors may be common for several amplifier circuits.

Abstract: A television apparatus includes a switching device for selecting different signal sources. In order to enable the supply of composite signals or "Y-C" signals at will to the input of one and the same circuit of the type having a "Y-C" input (two separate terminals), a filter eliminating the chrominance signal is arranged at the input "Y" and a filter eliminating the luminance signal is arranged at the input "C", whereas in a circuit of the type adapted to utilize a composite input signal, the input thereof is connected to a source for a signal of the type "Y" by means of a bridge comprising two series-arranged resistors, while the junction point of this bridge is connected to a source for a signal of the type "C" by means of a capacitive inductance resonance circuit of the series type which is tuned to the chrominance subcarrier frequency.

Abstract: A television set includes a circuit for modulating the horizontal velocity of the beam scan as a function of the video content with the aid of an auxiliary line deflection coil. The beam scan velocity modulation circuit includes a video signal differentiator circuit followed by an amplifier provided at the output of a power stage of the current generator type, which has its output connected to one terminal of the auxiliary line deflection coil. A voltage amplifier is provided at the output of a power stage of the voltage generator type which has its input connected to the output of the differentiator circuit, and its voltage output connected to the other terminal of the auxiliary line deflection coil.

Abstract: An amplifier includes amplifier transistor (3) whose collector is connected to a load impedance (12) which is a current generator and includes a device for controlling the current as a function of the voltage level at the collector (20) of the amplifier transistor, which control acts in such a way that the current decreases when the voltage increases with a time constant which is of the order of the field retrace period. The amplifier transistor (3) is of the NPN type and the power supply is positive, while the current generator is a PNP transistor (7) whose base is connected to the collector of the amplifier transistor (3) via a resistor (4).

Abstract: The readjustment of the image contrast is effected by a processing circuit (12) of the video signal, provided with a contrast control terminal (21). Among the devices which automatically act on the contrast, the device for comparing the peak values of the video signal to a reference threshold (Vref) is also used for manual adjustment. The gain of the amplification of the video signal in the processing circuit is increased such that, for the majority of images, the peak values of the video signal reach the reference threshold (Vref), while a user control varies this reference threshold to effect the manual adjusting.

Abstract: Automatic adjusting device: an oscillator followed by an inverter feeds the resonant circuit, which is followed by a frequency discriminator. The circuit is, for example, the "cloche" circuit of a SECAM decoder unit. The discriminator then forms part of the television set. A synchronizing source applies line and field synchronizing signals and a color identification signal to a synchronizing signal and window generator. The latter applies to the inverter a signal which triggers the inversion of the signal coming from the oscillator, which produces a 180.degree. phase jump. It also applies to a measuring and processing circuit a time window which is used during the measurement at the output of the discriminator of the transient signal produced by the phase jump. The result of the measuring operation is applied to an element which acts on the adjustment of the resonant circuit.

Abstract: A circuit for "fast" switching in television system when there are more than two video sources (1, 2, 3) to be switched simplifies the realization of the change-over switches (5, 6) by replacing one or a plurality of fast change-over switches by a slow change-over switch (6), which is possible if the control signal (7) of the slow change-over switch (6) is maintained during at least one field with the aid of a timing circuit (9).