Abstract: A PLL circuit for a phase comparator, a low-pass filter (LPF), a voltage-controlled oscillator (VCO) and a frequency divider. A first control circuit is responsive to a discontinuous phase change of a reference signal of the PLL circuit for inhibiting the operation of the phase comparator or disconnecting the LPF from the phase comparator during a predetermined period so that the discontinuous phase change information is not transmitted through the LPF to the VCO. At the same time, a second control circuit resets the frequency divider by a pulse of the reference signal after the discontinuous phase change or applies a voltage corresponding to the discontinuous phase change to the VCO so that the output signal of the frequency divider is locked in phase to the reference signal after the discontinuous phase change. With the cooperation of the first and second control circuits, the PLL circuit quickly recovers its stable state after the discontinuous phase change of the reference signal.

Abstract: A video signal processing apparatus incorporates a 1H or 2H delay circuit, wherein H is a horizontal synchronization period. The output of the delay circuit is fed back to the input thereof so as to average the noise, thus raising the signal S/N ratio. The feedback line includes a nonlinear processing circuit which has a small gain when the signal input has a low vertical correlation, whereby the signal S/N ratio is improved without causing the delay of the color signal in the vertical direction nor the deteriorated resolution of the luminance signal.

Abstract: A signal processing circuit for certainly detecting presence or absence of a change in the vertical direction of amplitude and phase of a chrominance signal by once converting the change in the vertical direction of amplitude and phase of the input chrominance signal into a change in the direction of amplitude by a converter, then comparing the converted output with a signal obtained by passing the converted output through one or a plurality of delay circuits by one or a plurality of comparing circuits in amplitude level, and then making an operation with the output of the comparing circuit by an operational circuit.

Abstract: A comb filter which shows a comb filter characteristic when a vertical correlation of an input signal is large and allows the input signal to pass as is when the vertical correlation is small includes a delay circuit for delaying the input signal by a predetermined time to obtain a delayed signal, a vertical correlation detecting circuit for detecting the vertical correlation of the input signal from the input signal and the delayed signal and for outputting a vertical correlation signal corresponding to the vertical correlation when the vertical correlation is large but not outputting any signal when the vertical correlation is small, and an operational circuit for operating upon the input signal and an output signal of the vertical correlation detecting circuit to obtain an output signal of the comb filter.

Abstract: A magnetic recording and playback apparatus for teletext signals which accurately records and reproduces the teletext signal superposed within the vertical blanking period of television signal, includes at least one wide band filter, at least one narrow band filter, a filter selection switch which switches at least one filter for a luminance signal processing system to the wide band filter and at least one filter for a chrominance signal processing system to the narrow band filter, and a control circuit which generates a control signal for controlling the filter selection switch. The control circuit generates the control signal only during a specified period where the teletext signal is superposed. In case a comb filter is used, a switch is provided for selectively passing an output of the comb filter and an input video signal to the succeeding stages and a control circuit for producing a control signal to allow the input video signal to pass during a specified period where the teletext signal is superposed.

Abstract: A video signal recording/reproducing apparatus for recording and reproducing a video signal onto and from a recording medium with a magnetic head. In this apparatus, the recording chrominance signal processing block is provided with a circuit for producing a continuous oscillation signal having the same frequency, gain and phase with those of a normal color burst signal, a switch for normally passing the chrominance signal and, at a period including the normal color burst signal and longer than the duration of the normal color burst signal, passing the continuous oscillation signal, so that a chrominance signal is obtained at the output of the switch with a duration expanded color burst signal. This chrominance signal is mixed with the frequency converted chrominance signal, and the thus mixed signal is recorded on the recording medium. The duration expanded color burst signal is contracted to the normal duration of color burst signal by a muting circuit in the reproduced chrominance signal processing block.

Abstract: A magnetic reproducing apparatus which has a pair of main rotatable heads having different azimuth angles and a pair of auxiliary rotatable heads having different azimuth angles. When a magnetic tape is played back while it runs at a speed different from that at which it runs during a recording mode, playback output signals from the main and auxiliary rotatable heads are switched over to replace a reduction in the outputs from the main rotatable heads with the outputs from the auxiliary rotatable heads to produce a combined playback output signal. The combined playback output signal is passed through a variable delay line having a delay time varied by an output from a detector circuit which detects variations in horizontal synchronous signal intervals of the combined playback output signal.

Abstract: A tracking-error correcting system in a rotary head magnetic recording and reproducing apparatus in which reproducing magnetic heads are mounted on a respective bimorph leaf having piezoelectric elements so as to be movable in the direction of the axis of rotation. The piezoelectric elements are controlled by a control voltage which is produced by adding a signal from an auto-tracking circuit and a signal from a triangular wave generating circuit. In a reproducing mode at a tape speed which is different from a tape speed in recording mode, this system activates the auto-tracking circuit when the control voltage level is within a limited range which is detected by a control voltage detector. Also, this system stops the auto-tracking circuit during a transition period when the reproduction mode changes.

Abstract: In a rotary head magnetic recording and reproducing system, the number of horizontal synchronous signals which occur between the vertical synchronous signals are kept almost constant by delaying the video signal of the field following the one in which a shift of a track has been detected, the operation occurring when the system is in the abnormal reproducing mode in which the speed of the magnetic tape in the reproducing mode is different from the speed of the magnetic tape in the previous recording mode.

Abstract: A video signal recording/reproducing apparatus includes a first set of rotary heads mounted on a rotary disk and a second set of rotary heads mounted on head actuators which are also mounted on the rotary disk. The apparatus has two reproduction modes. A magnetic tape in the first reproduction mode is driven at a speed equal to the speed used in a recording mode. The magnetic tape in the second reproduction mode is driven at a speed which is different from the speed used in the recording mode. The apparatus has a negative feedback loop which detects the reproduced signal level of the second set of rotary heads and drives the head actuators in order to increase the reproduced signal level of the second set of rotary heads. In the first reproduction mode, the negative feedback loop is intermittently closed.

Abstract: In a rotary head magnetic recording and reproducing system, the continuity of the horizontal synchronous signals are obtained during an abnormal reproducing mode in which the speed of the magnetic tape in the reproducing mode is different from the speed of the magnetic tape in the recording mode by delaying the video signal for a predetermined time and repeating this operation for each field.

Abstract: A tracking-error correcting system in a rotary head magnetic recording and reproducing apparatus in which the reproducing magnetic heads can move in the direction of their axis of rotation by using a bi-morph leaf having piezoelectric elements. This system can automatically detect the tracking-error between the reproducing head and a recorded track, and move the reproducing head in a direction to attain better tracking position while the head is not in contact with the magnetic tape, so that either head's scanning trace is always parallel to the recorded track. The system is protected from jitter or color flicker on the monitor television screen when the heads move in the direction of their axis of rotation.