Abstract: Device for reading-out a disk-shaped record carrier. To compensate for time-base errors of the detected signal caused by eccentricity or out-of-roundness of the record carrier, a tangential tracking system is provided with which the tangential position of the scanning point on the record carrier can be controlled. A control signal for this tangential tracking system is obtained by extracting the line synchronizing signal from the detected video signal. By ensuring through the use of a filter element that the overall transfer function of the control system exhibits a band-pass characteristic about the frequency which corresponds to the speed of the record carrier, a suitable tangential tracking is ensured.

Abstract: A playing apparatus, in particular a video player, for playing round records provided with information tracks and comprising a housing with a substantially flat covering plate, a drive spindle, a cover which is hinged to the housing and a stabilizing plate which is resiliently connected to the cover. On the cover a number of supports are provided which when the cover is closed support the stabilizing plate at a height which is accurately defined relative to the covering plate.

Abstract: A digital data transmitter is described, whose line carrier frequency need not be an integral multiple of one half the clock frequency of the digital input signal. Use is made of a digital filter for increasing the sampling frequency to a value which is twice the modulator carrier wave frequency.

Abstract: In an optic relay device having a memory the image to be treated is projected on a photoconductive element and is transformed into a charge image stored in a memory in the proximity of a plate of electro-optical material brought at its Curie point.The electro-optical material and the photoconductive element are such that the Curie temperature of the electro-optical material is near the temperature of the maximum sensitivity of the photoconductor.

Abstract: Apparatus for synchronizing the head wheel of a video tape recorder with the recorded signals uses a variable frequency oscillator controlled by the phase difference between recorded vertical synchronized signals and signals received from a vertical reference oscillator to provide a horizontal reference signal. The horizontal reference signal is compared with recorded horizontal synchronized signals as a fine control during playback.

Abstract: A device for the compensation of dropouts in an angle modulated signal. The device comprises a variable delay line, which receives a control signal from a control unit for variably delaying said angle-modulated signal. The control unit comprises a dropout detector and a transformation means co-operating therewith for supplying an output signal which is representative of the magnitude and the polarity of the dropout. Said output signal is applied to the variably delay means as a control signal.

Abstract: A record carrier is described on which information is stored in an optically readable structure of trackwise arranged areas and intermediate areas. By giving at least one of the surfaces of the record carrier body excursions which are periodically variable in the track direction, it is possible in a simple manner to obtain an indication of the focussing of the read beam on the information structure during reading of the record carrier.

Abstract: A disc-shaped information carrier is described which contains spirally arranged image and/or sound signals coded in optical form. By recording the information in at least two spiral information tracks which may be separately read the total amount of utilizable information may be increased by a factor equal to the number of information tracks.An apparatus for reading the information carrier is disclosed which there is inserted in the path of the read beam radiation from a source of radiation to a radiation-sensitive detection system an optical system for selectively converging the read beam on each track, whereby the tracks may be read without turning over the information carrier.

Abstract: The invention relates to a device for reading digital information which is stored as a bivalent state of a moving carrier, for example, the magnetization direction of a tape. Reading causes a differentiating effect. A coil of the read member constitutes, in conjunction with a parallel connected capacitor, a resonant filter having a mediocre Q factor, so that the signal components of comparatively high frequency are slightly amplified. The output of the resonant filter has connected thereto an amplifier. A branch line for comparatively low frequencies with a filter having a drooping amplitude/frequency characteristic is connected to the amplifier. A branch line for comparatively high frequencies in which a filter having a rising amplitude/frequency characteristic is included is also connected to the amplifier.

Abstract: A transmission system for pulse signals of fixed clock frequency having repeaters located in the transmission path, each of which is provided with an adjustable equalizing amplifier, a pulse regenerator and a clock extraction circuit. In addition to the pulse signals a pilot signal synchronized with the clock frequency is transmitted which is synchronously mixed with a local pilot signal derived from the clock extraction circuit. From the mixing product an adjusting signal for automatic equalization is derived which is reliable under all conditions. The resulting simplicity of structure and implementation of the equalizing amplifier renders the transmission system particularly suited for pulse signals at a very high clock frequency.

Abstract: An opto-electronic system is described for determining a deviation between the actual position of a radiation-reflecting plane in an optical imaging system and the desired position of said plane. Two auxiliary radiation sources are provided which are shifted in opposite directions relative to the optical axis of the imaging system and two radiation-sensitive detectors which are also shifted in opposite directions relative to the optical axis of the imaging system. Of the set of auxiliary radiation sources and the set of detectors the elements of one set are shifted relative to each other in the direction of the optical axis. The auxiliary radiation sources may be formed with the aid of a Fresnel zone plate.

Abstract: An apparatus is described for reading a record carrier on which information is stored in an optically readable reflecting structure. By projecting two radiation spots one before and one behind the plane of the information structure, it is possible to ascertain whether a read beam is properly focussed on the information structure.

Abstract: An apparatus is described for reading a radiation-reflecting record carrier on which information is stored in an optically readable structure. For separating the modulated and the unmodulated read beam, the radiation path from the radiation source to the record carrier includes a beam-splitting element with such a reflection coefficient that only a small part of the modulated read beam returns to the radiation source, while a sufficiently large part of said beam reaches a radiation-sensitive detector.

Abstract: An apparatus for reading a record carrier on which a combined video signal is recorded in a single track, in particular a disc-shaped record carrier on which the signal is recorded in optically coded form. In order to reduce the disturbing effect of dropouts on the eventually obtained sound signal, a portion of the the video signal is subjected to the action of a clamping circuit. Said clamping circuit normally transfers the applied modulated video signal unmodified. During a dropout the modulated video signal consisting of the modulated sound and pilot signal is clamped at its average value by means of said clamping circuit, so that a substantial improvement is obtained in respect of the sound signal. Thus, the length of time of sound signal clamping is minimized and the sound quality is improved.

Abstract: Utilizing a known equalizer and a single-sideband frequency transposition device, unitary construction is achieved by using a second series of output channels which, by a crosswise connection to the comparators already present in the control voltage generator, supplies a second equalized signal shifted in phase over .pi. /2 with respect to the equalized output signal of the first series of output channels. The output signals thus formed are used as input signals for a single-sideband frequency transposition device having two modulator stages which are also fed by two frequency transposition oscillations mutually shifted in phase over .pi. /2. In this way a unitary construction is realized which is especially interesting for integration and which distinguishes itself by an optimum frequency transposition quality as well as by a considerable saving in complex circuit elements.

Abstract: An impedance matching circuit for a pushbutton telephone uses two voltage regulating transistors having their emitter-collector terminals connected in parallel with a potentiometer, the output terminals of the telephone set, and the output of a pushbutton tone generator amplifier. The base terminal of one of the transistors is connected directly to a tap of the potentiometer, while the base of the second transistor is connected to a further tap on the potentiometer through a low pass filter.

Abstract: Frequency demodulator for a frequency-shift-keying data transmission system, which demodulator comprises, in cascade, a monostable circuit, a lowpass filter and a voltage comparator to which a threshold voltage is applied. The demodulator further comprises a switch which is operated by the monostable circuit and supplies to the lowpass filter either one or the other of two voltages derived from the same supply source and having different polarities. The threshold voltage is fixed at zero and in order to correct the bias distortion one of the said two voltages is adjusted.

Abstract: A clamping device for rotatably driving an information carrying record such as a rigid or flexible video record and comprising a drive spindle, a record support disposed thereon, a substantially conical centring member having a diameter which varies from a diameter smaller than to greater than that of the record hole, which also during operation co-operates with the edge of the central hole in the record, and furthermore resilient pressure means for pressing the centring surface and the edge of the central hole in the record against each other.

Abstract: Equalizing system arranged for pulse transmission, adaptive equalization being achieved without the use of an additional periodic adjusting pulse pattern. For this purpose in a control voltage generator the sub-bands and the associated additional sub-bands of an equalized pulse signal processed by the phase and amplitude control circuits are used after pulse regeneration directly as a local reference signal and an adjusting signal respectively. The sub-bands and additional sub-bands are applied to the cascade connection of a comparator and a mean-value device for generating the control voltage which controls the phase and amplitude control circuits in a feedback mode.

Abstract: The invention relates to a recording and playback apparatus for video signals including a drive shaft for driving a record carrier, whose revolution speed can be controlled by a servo system, and a switching device to ensure that a new recording without interruption follows an existing recording, said apparatus comprising a measuring and storage device for measuring and storing the difference in phase between the pulses supplied by the tacho-generator and the pulses scanned from the synchronizaton track which device is followed by a comparator, for comparing the stored measuring value with the reference signal for the servo system, which comparator if its input signals are equal supplies its output signal to the servo system as the measuring signal. Such a servo system prevents the occurrence of undesired phase shifts at the transition from the existing recording to the new recording.