Hitachi, Ltd.

Hitachi Microcomputer Engineering, Ltd.

Hitachi Video Engineering, Incorporated

Hitachi Computer Engineering Co., Ltd.

Hitachi Video Eng. Inc.

.Engineering, Inc.

Hitachi Microcomputer Hitachi, Ltd.

Hitachi Video Engineering Co., Ltd.

Hitachi Microcomputer Eng. Co.

Isao Fukushima

Hideo Nishijima

Yasunori Kobori

Kuniaki Miura

Yoshinori Okada

Kaneyuki Okamoto

Kenji Kano

Hiroyuki Kimura

Takayasu Ito

Masataka Sekiya

Yoshinori Masuda

Kazuyoshi Kuwahara

Norio Minami

Yoshimi Iso

Makoto Shiomi

Isao Akitake

Keiichi Itoigawa

Katsumi Sera

Kazuya Takahashi

Akihiro Asada

Takashi Kubota

Tomishige Yatsugi

Kenji Satoh

Harushige Nakagaki

Mitsuru Kudo

Eiji Moro

Teizo Tamura

Norihisa Yamamoto

Hajime Yokota

Shin-ichi Ohashi

Fumiaki Fujii

Tadashi Takamiya

Masao Hibi

Hiroshi Shirai

Tetsuo Sakae

Syunji Iwasaki

Yasufumi Yunde

Hideo Yoshida

Hiroshi Toeda

Tunehiko Teshima

Tsunehiko Teshima

Katsuhiko Goto

Kazunori Kotani

Takashi Takahashi

Susumu Otsuka

Hisaji Watanabe

Shigeaki Kanenari

Yoshio Fujimori

Eiichi Funaki

Takashi Furutani

Shin-Ichi Ohashi

A preamplifier circuit for amplifying a video signal reproduced by a magnetic head includes a positive feedback circuit for reducing an input capacitance thereof. A negative feedback circuit may be added thereto for stabilizing an operation of the preamplifier.

Video signal preamplifier circuit

The invention is to provide a more economical and practical multi-channel inverter with reference particularly to a modulation process of the time width, wherein a DC output is fed to each of a multiplicity of output channel circuits through time division to a multi-channeling, each of the time widths is modulated pertinently according to each output, thereby obtaining DC and AC multi-channel outputs independently of each other between said channels.

Multi-channel inverter circuit

In a slow-motion device of a helical scan type video tape recorder, detection is effected to detect a noise in a reproduced signal which is caused when the magnetic tape is fed such that the magnetic heads which have reproduced a preceding still image at a track transfer to the succeeding track and thereafter the magnetic heads scan the succeeding track, and the position of the magnetic tape is controlled by a tape control system so that the noise is confined within a position at a noise bar due to the noise is prevented from being displayed on the reproduction screen.

Slow-motion device of magnetic recording and reproducing apparatus

An auto-tracking apparatus of a magnetic recording/reproducing apparatus has a circuit for discriminating whether the audio signals recorded on a magnetic tape to be reproduced were recorded by audio rotary heads or a fixed head, and a circuit for selecting outputs of the audio rotary heads in the case of the Hi-Fi recorded magnetic tape by the audio rotary heads and outputs of the video rotary heads in the case where it is determined that the magnetic tape is the normal recorded tape by the fixed head on the basis of the result of the discrimination, and performs the auto-tracking on the basis of the selected outputs. With this arrangement, the auto-tracking can be carried out irrespective of whether the magnetic tape is the normal recorded tape by the conventional fixed head or the Hi-Fi recorded tape by the rotary heads.

Auto-tracking apparatus of a magnetic recording/reproducing apparatus

A still picture reproducing system for a magnetic recording and reproducing apparatus is disclosed. The system sends one frame in order to shift a reproduction mode from ordinary reproduction to reproduction of a still picture by use of so-called 'fine slow', sends one more frame if a noise is detected on a picture at this time, and stops if no noise is detected.

Still picture recording system with noise detection and frame counting

An integrated filter circuit including at least integrated resistances and integrated capacitances, said integrated filter circuit comprising a plurality of filter circuits connected in parallel and in which at least either resistance values or capacitance values are different, a switch for switching said parallel filter circuits, and means for controlling said switch to select one of said parallel filter circuits.

Integrated filter circuit having switchable selected parallel filter

In a magnetic recording circuit with a bias current circuit adapted to superimpose a bias current from a bias oscillator on a recording signal and to supply a resultant signal to a magnetic head, there is provided a resistor for detecting the bias current flowing through the magnetic head, a rectifier circuit for rectifying and smoothing a signal developing across the resistor, and a control circuit for comparing the output voltage of the rectifier circuit with a reference voltage and producing an output signal which controls the oscillation level of the bias oscillator, whereby the bias current flowing through the magnetic head can automatically be set to a predetermined level. A variable resistor for adjustment of the bias current and adjustment step for the variable resistor can be dispensed with.

A recording circuit having means to automatically set the recording

A recording circuit for a video tape recorder which records superposedly a frequency-modulated audio signal with a frequency-modulated luminance signal and a carrier color signal converted to a low frequency band records a carrier wave signal which is frequency-modulated by the luminance signal at a substantially constant recording current within the frequency range corresponding to a range from the sync signal leading edge to the white peak. In an ordinary recording circuit, the extent of erasure of the recorded audio signal varies with the content of the frequency-modulated luminance signal when the luminance signal is recorded on the recording track of the frequency-modulated audio signal, because recording is made by increasing a recording current for a signal having an instantaneous frequency which is low. Therefore, the recorded signal which is frequency-modulated by the audio signal is amplitude-modulated by the luminance signal, and interference with the audio signal due to the change of S/N corresponding to the change of the amplitude occurs. In the recording circuit of the present invention, however, no interference is applied to the audio signal because the extent of erasure of the recorded audio signal by the luminance signal remains substantially constant irrespective of the content of the luminance signal.

Apparatus for multiplex recording and reproduction of audio and video

A motor driving circuit includes an equivalent power PNP transistor constituted by a Darlington connection of a small-current PNP transistor and a large-current NPN transistor, and a switching regulator of a step-down and variable type is provided between the collector of the NPN transistor and the emitter of the PNP transistor. Electric power loss in the motor driving circuit can be reduced, and the electric power required to operate the motor driving circuit can be saved.

Switching regulator system for a motor driving circuit

A VTR is furnished with a phase-locked loop whose reference input is a color signal subcarrier. The phase-locked loop fixes two sound FM carrier frequencies in constant relationships with the frequency of the color signal subcarrier, thereby to stabilize the carrier frequencies. The two sound FM carrier frequencies are respectively selected to be integral times of f.sub.H /2 (where f.sub.H denotes the frequency of a horizontal synchronizing signal). The frequencies of the beats between both the sound carrier are fixed to integral times of f.sub.H /2, with the result that the degradation of a reproduced picture attributed to the beats is prevented.

Magnetic recording apparatus with recording of first and second sound

The IC chip consists of electronic circuits wherein voltage control oscillator whose oscillation frequency is dependent on the product of the resistance value of a resistor element and the electrostatic capacity of a capacitor element is provided; said capacitor element consists of the first variable capacitor; said voltage control oscillator comprises said capacitor consisting of said first variable capacitor; said first variable capacitor is controlled by the output obtained by detecting the output signal of said voltage control oscillator by its phase, using the predetermined reference signal, whereby the oscillation frequency of said voltage control oscillator can be made to agree with the frequency of said reference signal. Furthermore, the characteristic of said electronic circuit is dependent on a second resistor element and a second variable capacitor element; said second variable capacitor is controlled by the output obtained by the phase detection so that dispersions of the resistance value of the resistor element and the electrostatic capacity of the capacitor element in said electronic circuit are absorbed automatically.

Integrated circuit with a phase-locked loop

A filter integrated circuit having a reference level generator circuit for attenuating its input signal and generating a reference level signal, a pseudofilter circuit including resistors and a variable capacitor as filter elements, and an error amplifier unit for comparing the level of the output signal of the reference level generator circuit with the level of the output signal of the pseudofilter circuit and for generating an automatic adjustment control signal in accordance with the level difference between the output signals. The automatic adjustment control signal is supplied to the pseudofilter circuit to change the capacitance value of the variable capacitor in the pseudofilter circuit so that the output signal level of the pseudofilter circuit may become equal to the level of the reference signal. The automatic adjustment control signal is also supplied to at least one filter circuit to change the capacitance of a variable capacitor included therein. As a result, the deviation in the filter characteristics caused by deviations in the resistance of a resistor and in the capacitance of the capacitor is corrected.

Integrated filter circuit with variable frequency characteristics

An apparatus for driving a brushless motor, in which a ripple appearing in the rotation torque of the motor is cancelled by driving the motor with a signal current whose phase is opposite to that of and which has a waveform symmetrical with that of the torque ripple waveform, so that the motor can rotate accurately without any speed variation. In order to obtain such a signal current waveform, counter-electromotive forces induced in the stator coils of the motor are detected, and the level of the signal indicative of the detected counter-electromotive forces is controlled depending on the load and rotation speed of the motor to provide a control signal for controlling the motor drive current.

Apparatus for driving brushless motor

Disclosed is a circuit for emphasizing a video signal in the vertical direction of a television picture for minimizing noise appearing during reproduction. In the circuit, a signal obtained by delaying an input video signal by one horizontal scanning period is positively fed back through a feedback circuit to the input of the input video signal. An amplitude difference signal between the video signal after being fed back through a positive feedback loop and the delayed video signal is produced and added to the input video signal to provide an output video signal.

Vertical contour emphasis de-emphasis circuit

An auto-tracking method and apparatus of a helical scan type magnetic recording/reproducing apparatus wherein envelope levels of reproduced signals are detected and the running phase of a magnetic tape is controlled so that the envelope level of the reproduced signal becomes maximum after detection is effected roughly and then finely, thereby allowing a video head to scan a track on the magnetic tape.

Auto-tracking method and apparatus of a magnetic recording/reproducing

Growing community of inventors

Katsuta, Japan

Isao Fukushima