U.S. Philips Corporation

Nico Valentinus Franssen

Karel E Kuijk

Gerardus Andreas Van Maanen

Mathias H Geelen

Johannes Willem Siebelink

Frans Josef Frankort

Henricus G Kockelmans

An amplifier comprising a first and a second amplifier element, whose outputs are connected to a load, a difference circuit which comprises a comparator, in which the output signal of the first amplifier element is compated with the input signal thereof to produce a correction signal which is applied to second amplifier element, and a second substantially identical difference circuit which comprises a comparator in which the output signal of the second amplifier element is compared with the input signal thereof to produce a correction signal which is applied to the first amplifier element; a desired signal to be amplified being applied to both amplifier elements. The two amplifier elements, which may be preceded by preamplifiers, take the form of power amplifiers. Because the distortion signals appear at the load as 'common mode' signals, the overall distortion becomes substantially zero in the case of equal attentuation in the two difference circuits. The power amplifiers may be provided with a voltage output as well as a current output.

Amplifier comprising a first and a second amplifier element

Noise reduction circuit for stereo signals comprising a control input terminal, first and second outputs as well as a controllable coupling circuit for a controllable mutual signal coupling between the two outputs, the two outputs being decoupled from one another only during those sound passages wherein an effective after-effect of a stereo impression is produced to obtain an optimal combination of noise level and stereo effect.

Noise reduction circuit for stereo signals

System for the vocoder transmission of speech signal with reduced bandwidth. The speech signal is split into a low-frequency part and a high-frequency part. The high-frequency part is subdivided into a number of sub-bands and for each sub-band a control signal with reduced bandwidth is transmitted. A control signal is representative for the ratio between the energy in the sub-band of the speech signal and the energy in the corresponding sub-band of a reference signal with high-frequency components, which is produced from the low-frequency part of the speech signal.

Compression system

A circuit arrangement for generating the tones of a tonal scale includes a master oscillator and a number of sets of frequency converters. The output signals of each set of frequency converters forms each of the tones of an octave. A frequency shifter is connected between at least one selected set of frequency converters and the master oscillator in order to shift the frequency supplied to the selected set of frequency converters from the master oscillator to cause a desired shift in the frequency of each of the tones of the octave produced by the selected set of frequency converters.

Circuit arrangement for obtaining a chorus effect

A coder and a decoder having delay elements of the same delay time arranged one after the other in which the signal transmission ratio code of the signal paths from the input of the circuit to the output is chosen in accordance with bessel coefficients so as to prevent disturbing echoes.

Signal transmission circuit comprising a coder and a decoder

A device for converting electric into acoustic vibrations and vice versa, provided with a diaphragm, comprising at least one layer of a piezoelectric polymer material, which is polarized in a transverse direction and which at either side is provided with electrodes, the diaphragm being undulated in at least one orthogonal section, whilst each flank of the undulation is polarized in the same direction over its entire width and in the operating condition the direction of the applied electric field relative to the direction of polarization in adjoining flanks are alternately parallel and anti-parallel. Two types of embodiments are possible. In the first embodiment the direction of polarization in each flank is opposed to that of at least one adjacent flank; in the second embodiment all flanks are polarized in the same direction, each flank being provided with a pair of electrodes which are oppositely disposed relative to each other, which pair is electrically isolated from a corresponding electrode pair of at least one adjacent flank, which last-mentioned pair in the operating condition has an opposite polarity relative to the first-mentioned electrode pair. The use of polyvinylidenefluoride as a piezoelectric material has been found to be very favorable.

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Eindhoven, Netherlands

Nico Valentinus Franssen