U.S. Philips Corporation

Rudolf A Van Doorn

Marino G Carasso

Frank De Jager

Franciscus J Verhallen

Petrus J Van Gerwen

Wilfred A Snijders

Gerardus H Somers

Abraham Hoogendoorn

Victor Zieren

Johannes J Verboom

Hendrik Arie Van Essen

Franciscus A Pronk

James Richard Peterson

Gerardus W Akkermans

Helmut J Gassen

Johannes F De Proost

Johannes H Franssen

Johannes V Verboom

Stephanus J Van Beckhoven

Pieter Tammo Bolwijn

A device for recording an information signal on a magnetic record carrier (2) includes a write amplifier (3), a magnetic head (4) of the magnetoresistive type, and a compensation circuit for controlling the amplitude of the write current in dependence upon temperature variations which occur during recording. The compensation circuit includes an actuator for bringing the record carrier into contact with the magnetic head (4) before a recording is started. In addition, detector means (17, 18) is provided to detect an output signal of the magnetic head produced as a result of the magnetic head being brought into contact with the record carrier. A control signal generator (17) generates a control signal whose magnitude is a measure of the magnitude of the output signal. The compensation circuit (3, 5, 8, 11, 17) is adapted to control the amplitude of the write current in dependence upon the control signal.

Recording device with temperature-dependent write-current control

A device for recording an information signal on a magnetic record carrier comprises a recording amplifier (3), a magnetic head (4), and a controller for controlling the write current amplitude in dependence on temperature variations which occur during recording. This is effected by a temperature detector. The magnetic head (4) has a write section (5) for recording an information signal on the magnetic record carrier in a recording mode of the device, and a read section (6) for reading an information signal from the record carrier in a playback mode of the device. The read section (6) is of the magneto-resistive type. The temperature detector is formed by the read section.

Recording device with temperature-dependent write current control

For a tape contact face to be formed in a thin-film magnetic head having at least one transducing element, by removing material, a reference plane (29) corresponding to the tape contact face is detected by means of a plurality of markers (27A-27J) juxtaposed in a layer and extending transversely to the tape contact face, which markers have first end portions (27A1-27J1) pointing in one direction and second, spatially separated end portions (27A2-27J2) pointing in an opposite direction, with the second end portions located at different distances from the reference plane, inclined with respect to the reference plane, and adjoining each other steplessly.

Method of manufacturing a thin-film magnetic head and magnetic head

The invention relates to a method of demodulating a quadphase coded data signal and a receiver for carrying out the method. The quadphase code comprises four elementary wave forms, each wave form representing two bits of the original non-coded binary signal. An elementary wave form consists of four half bit intervals, the signal corresponding to the first and the second bit, respectively, being transmitted in the first and the second half bit interval and the signal corresponding to the inverted value of the first and the second bit, respectively, being transmitted in the third and the fourth half bit interval. In a receiver according to the invention such a signal is sampled in each of the four half bit intervals. In principle all information is already available after the sampling operations in the first and the second half bit interval, but by utilizing all four samples a proper protection from noise, interference and zero level shifts is obtained. The receiver determines the difference of the samples taken in the first and the third half bit interval and the difference of the samples taken in the second and the fourth bit interval. A positive difference represents a logic 1, a negative difference a logic 0.

Method of demodulating a quadphase coded data signal and receiver for

The invention relates to a method for the clock synchronization of a receiver for demodulating a quadphase coded data signal and to a clock synchronization device for carrying out the method. In the method according to the invention the first bit is compared (correlated) with the third bit and the second bit with the fourth bit: a high degree of correlation indicates that synchronization has been obtained and a low degree indicates absence of synchronization.

Method of synchronizing a quadphase receiver and clock synchronization

A digital filter and demodulation arrangement for passband signals, whose corresponding baseband signal has a bandwidth limited to a given maximum frequency. The passband signals are filtered according to two bandpass characteristics which, apart from their asymmetrical distortion relative to their central frequency, are versions from one another shifted 90.degree. in phase. The filtered passband signals are demodulated with an in-phase carrier and a quadrature carrier and the demodulated signals are combined to a baseband signal. In the digital filtering process the sampling frequency is reduced from a value higher than twice the highest frequency in the passband signals to a value which is not higher than twice said maximum frequency in the baseband signal and in the digital demodulation and combination processes the reduced sampling frequency is also used so that a considerable reduction in the internal processing speed is obtained.

Filter and demodulation arrangement

An energizing circuit for a redox display device in which a criterion for terminating the registering or erasing action is provided for the energizing electrodes.

Energizing circuit for a visual display element

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Eindhoven, Netherlands

Rudolf A Van Doorn