Abstract: In accordance with a method of recording and/or reproducing stereophonic information in two adjacent tracks of a magnetic record carrier, an auxiliary signal whose frequency content is situated outside the frequency spectrum of the stereophonic information is recorded in the tracks and in the magnetic record-carrier area between the tracks during recording. During reproduction, the auxiliary signals read from the record carrier by the two transducers is used to control the gain of a pair of variable amplifiers so as to ensure that the amplitudes of the stereophonic information signals thus reproduced are independent of tracking errors.

Abstract: A tape recorder or player with automatic azimuth control, utilizing a single pieozoelectric element inside the head's magnetic shield. A bimorph has one end rigidly connected to the head and the other end rigidly connected to the head support, for pivoting the head about an axis in line with the head gap.

Abstract: A magnetic tape recorder or playback apparatus, especially suitable for tape having a large number of parallel longitudinal tracks, has a positioning device for independently correcting tracking and skew errors. A first positioning system uses two piezo-electric elements parallel to each other and equally spaced on opposite sides of the pivot axis, and a second positioning system arranged between the first two piezo-electric elements, having at least three piezo-electric elements regularly spaced around and extending longitudinally about the pivot axis.

Abstract: A phase comparison circuit for producing an output signal which is a measure of the phase difference between first (A) and second (B) pulse trains applied to respective first and second inputs thereof. The circuit is immune to the omission of a pulse from one of the trains and to pulse length inequality in the two trains. It comprises a logic circuit, two switchable current sources connected to a capacitor (17), a switchable constant voltage source, i.e. a controllable switch (18) connected to the capacitor, and a sampling circuit connected to the capacitor.

Abstract: A method of and a device for automatically compensating the error in the angular position of a reproducing head, the upper half and the lower half of a track being scanned simultaneously, while the time difference between the zero passages of the signals is determined and a signal for the compensation of the angular error is derived therefrom.

Abstract: A device for receiving analog and discrete input signals and for converting the spectrum thereof without loss of information. The resultant signal has a frequency response curve which exhibits zero points at the frequency zero and at half the sample frequency. The second zero point is then suitable for addition of a pilot tone, without the required bandwidth being increased and without interference with the data signal. The device comprises two integrating feedback loops (32, 24/40), the output signals of which are alternately activated. The sign of the active output signal determines the sign of the input signal of the feedback loops and of the output signal of the device. One feedback loop directly receives said output signal, while the other feedback loop receives this output signal via a multiplier which alternately receives a positive and a negative multiplicand.

Abstract: A device for controlling a piezo-electric positioning element. In order to ensure that said element occupies a well-defined rest position, the device comprises a circuit for generating an electrical oscillation whose amplitude decreases to zero as a function of time and which varies symmetrically about a reference value, and for applying said oscillation to the piezo-electric element, so that hysteresis effects are eliminated.

Abstract: A device for the generation of a control voltage across a piezo-electric positioning element. In order to enable a high voltage to be generated across the piezo-electric element without using a comparatively high supply voltage, use is made of the capacitance of such an element as an integrating element. The device comprises a current source and switches for transferring current pulses to and from the piezo-electric element on command of control pulses.

Abstract: A recording and/or reproducing apparatus for a record carrier in the form of a tape, with a plurality of parallel longitudinal tracks. The apparatus comprises positioning means for controlling the position of the write/read head transverse to the direction of movement of the record carrier. The control signal for these positioning means is obtained with the aid of two optical systems, which each comprise a light-emitting element for emitting a radiation beam which is aimed at one edge of the record carrier and a light-receiving element for picking up the amount of light which shines past said record carrier, at least one of the elements of each optical system being rigidly connected to the write/read head. A detection device is coupled to the two light-receiving elements, which device derives the desired control signal from the amounts of light received by these two light-receiving elements.