Abstract: An method to prevent excessive heat generation of the pickup actuator from occurring when a disk has a large eccentricity or planar vibration in a high-speed disk reproducing apparatus using an optical pickup. The disk reproducing apparatus has a status determining arrangement for monitoring a present actuator drive state, an analyzing arrangement for analyzing an output signal of the status determining arrangement, and disk rotational speed switching control arrangement for selecting disk reproducing speeds according to a control signal of the identification means, thereby lowering the reproducing speed when the eccentricity or planar vibration is large. Such invention prevents heat generation of the pickup actuator from occurring because high-speed reproduction can be performed when the eccentricity or planar vibration is small, and reproduction speed can be automatically reduced when the eccentricity or planar vibration is large.

Abstract: The helical scan reproducing apparatus for magnetically recorded digital information signal reproduces the digital information from the magnetic tape wrapped around the rotary cylinder. The digital information signal is recorded on a plurality of recorded tracks of the magnetic tape. The magnetic heads of the rotary cylinder scan the recorded tracks to reproduce the digital information signal. The reproducing apparatus has the standard playback mode in which it is operated to reproduce at the standard speed and the fast playback mode in which it is operated to reproduce at a higher speed than the standard speed. The tracking control in the reproducing apparatus controls the speed of the magnetic tape so that in the fast playback mode the magnetic heads precisely trace the particular regions of the tracks which particular regions have data for fast playback mode recorded. Each of the tracks is divided into a plurality of blocks.

Abstract: A magnetic recording/reproducing apparatus is provided which includes a head structure compatible with a long-time play mode in handling either of two kinds of signals containing different amounts of information, such as a current digital picture signal and a high-definition (HD) digital picture signal in the rate of two to one at a constant number of revolutions of the drum by restricting an increase of the number of heads. In an aspect of the apparatus, four heads are arranged on the rotating drum equally 90.degree. spaced, a fifth head of an opposite azimuth is mounted close to any of those heads, the number of drum revolutions is increased to twice larger than the normal number, the current digital picture signal is recorded and reproduced for each channel by using two heads, that is, the fifth head and a head positioned 180.degree. opposite to the fifth head.

Abstract: A magnetic recording/reproducing apparatus for recording a signal onto a magnetic tape and reproducing a recorded signal comprises magnetic heads mounted on a rotary cylinder, a tape driving mechanism, high speed running control device for driving a reel shaft to rotate at a speed higher than a normal recording/reproducing speed, tape-running detecting device, reel motor starting device for generating a ramp voltage having a suitable gradient, a switch for turning on/off the tape running speed control by the high speed running control device and adding device. In the apparatus the cylinder rotation speed follow-up control never comes out in making the high speed running of the tape rise, so that the relative speed between the head and tape is maintained to substantial constant.

Abstract: A composite wobbled tracking servo system uses a rotary optical disc which has a header field and a data field alternately arranged along the direction of rotation to provide a sector, and which includes pregrooves formed in at least the data field and at least one pair of wobbled track marks disposed in the header field in a relation wobbled relative to the center of a track. A light spot is directed toward and onto the optical disc to detect a push-pull tracking error signal from the reflection of the light spot diffracted by the pregroove, and a wobbled tracking error signal is detected from the reflection of the light spot traversing the wobbled track marks. The push-pull tracking error signal is corrected on the basis of the wobbled tracking error signal to attain the tracking control with higher accuracy, thereby eliminating an undesirable track offset attributable to tilting or eccentricity of the optical disc.

Abstract: A composite wobbled tracking servo system uses a rotary optical disc which has a header field and a data field alternately arranged along the direction of rotation, and which includes pregrooves formed in at least the data field and at least one pair of wobbled track marks disposed in each of the header fields in a relation wobbled relative to the center of a track. A light spot is directed toward and onto the optical disc to detect a push-pull tracking error signal from the reflection of the light spot diffracted from the pregroove, and a wobbled tracking error signal is detected from the reflection of the light spot passing the wobbled track marks. After attenuating the gain of the wobbled tracking error signal by a low-pass filter so that the gain of the wobbled tracking error signal becomes equal to that of the push-pull tracking error signal at a frequency fe satisfying the relation1/50.multidot.N.multidot.fd<fe<1/5.multidot.N.multidot.

Abstract: In a disc playback apparatus using an optical pickup or the like, any flaws on a track of the disc are detected using: a first level detector for detecting a maximum value level of a recording information signal of an output of the pickup; a second level detector for detecting a change of the maximum value level of the recording information signal; and a comparator for comparing outputs of the above first and second level detectors. When any flaws are detected, a driving signal of a driving device for the pickup is held to a fixed reference potential.

Abstract: A reproducing rate control apparatus for an information recording disc in which pieces of information and absolute times for respective information pieces (representative of the reproduction time measured from the innermost circumference of the information recording disc) are recorded on the disc at a constant linear velocity, a revolution number of the disc at a command position is predicted, rotation of a disc drive motor is controlled so that the disc rotates at a predicted revolution number, and an information reader adapted to read the information recorded on the disc is moved to the command position when the revolution number controlling is effected or after the revolution number controlling has been completed.

Abstract: A servo circuit for a signal reproducing apparatus for reproducing signals from a record medium such as a disc utilizing an optical pickup, wherein a variable gain amplifier is arranged in a servo loop between a pickup and an actuator so that the pickup is caused to track a signal track in accordance with a servo error signal produced by the variable gain amplifier. A playback condition of a disc is discriminated by detecting the number of errors in a signal reproduced from a recorded signal on the disc by the pickup, and a gain of the variable gain amplifier is controlled by the discrimination output so that the variation of the servo error signal caused by a difference in reflectance between individual discs is eliminated and a loop gain appropriate to an individual disc is automatically set.

Abstract: In a power amplifier having a power circuit of a switching control system, a protective device for the power amplifier has connected to the amplifier a means for detecting an abnormal signal produced at the amplifier, and a control means connected between the detecting means and the power circuit to the amplifier so as to cut off a switching control signal to the power circuit when an abnormal signal is generated at the amplifier, thereby stopping the power circuit from operating to cut off power to the power amplifier. The detecting means is formed of a detecting circuit connected to the output end of the amplifier so as to detect the DC output voltage or excessive current from the amplifier, and a driving circuit connected to the detecting circuit so as to be operated by the output signal from the detecting circuit.

Abstract: A power supply controlled stereophonic amplifier system of a simplified circuit configuration which includes an analog logic circuit that generates a larger one of the input signals for left and right channels thereby to control the output voltage of the DC-DC converter as a power supply by means of a pulse train of pulse widths that change according to the output of the logic circuit. The output of the analog logic circuit is compressed by a signal compression means which functions to compensate for the non linear response of the DC-DC converter.

Abstract: A first pulse train has repetition pulses in proportion to the frequency of an input signal. A second pulse train has repetition pulses obtained by shifting the timing phase of the pulses of the first pulse train. One of the pulse trains is used to drive a saw-tooth wave generator circuit, thereby producing a saw-tooth wave voltage, which is supplied to a sample-and-hold circuit, which in turn is driven by the other pulse train so that the saw-tooth wave voltage is sampled and held, thereby producing a DC voltage.

Abstract: An audio frequency power amplifier wherein an input signal is applied to respective input electrodes of a pair of transistors of the same conductivity type to produce an output signal at an output electrode of one of the pair of transistors. A common electrode of the one transistor is connected with an output electrode of the other transistor and a power from a first D.C. power supply is supplied to the junction thereof through a diode while a power is supplied to a common electrode of the other transistor from a second D.C. power supply having a higher voltage than that of the first D.C. power supply. The other transistor and the diode are alternately rendered conductive and non-conductive in response to the signal level of the input signal, a capacitor is connected to the input electrode of the other transistor, which capacitor is charged during the turn-off of the other transistor whereby the charge is supplied to the other transistor upon turning on of the other transistor to shorten the rise time.