Abstract: A frequency modulated (FM) signal is recorded as pits or dots along a track formed as a concentric or spiral shape on a recording medium such as a recording disc. The pits or dots are arranged on a radial line during at least a predetermined interval.

Abstract: This invention reduces crosstalk interference components without a significant increase in recorded bandwidth of the modulated audio signals and without a significant degradation of the signal-to-noise ratio of the reproduced audio signals. According to the invention, the nominal carrier frequency of the modulated audio signals in adjacent tracks or scans is offset by an amount sufficient to shift the crosstalk interference components outside the desired audio pass band for substantially all modulating amplitudes and frequencies. At the same time, the modulated audio frequency spectra of the adjacent tracks substantially overlap so that additional overall bandwidth requirements are minimized. A satisfactory offset from track to track is in the order of twice the maximum audio response frequency. As the offset is reduced or as occasional high frequency high amplitude audio occurs in adjacent tracks, crosstalk distortion components will tend to appear beginning at the high frequencies.

Abstract: A modulator-demodulator suited to record an audio signal in a recording medium in the form of a frequency-modulated signal and to demodulate the frequency-modulated signal is disclosed. It includes a voltage-controlled oscillator, a switching circuit for changing one of two input frequency-modulated signals toward a control input of the voltage-controlled oscillator, and a phase detector for detecting a difference in phase between the frequency-modulated signal reproduced from the recording medium and the output signal of the voltage-controlled oscillator. In a recording operation, an input audio signal is supplied to a control signal input terminal of the voltage-controlled oscillator through the switching circuit, and the VCO acts as a modulator for carrying out frequency modulation.

Abstract: In order to reproduce an image signal from a frequency modulated wave which is obtained by frequency modulating a carrier with the image signal and picked-up from a magnetic tape by means of a magnetic head, the picked-up frequency modulated wave is supplied to a high pass filter for deriving a frequency modulated fundamental wave which is then supplied to a first limiter circuit to derive a first rectangular wave in response to zero crossings of the fundamental wave. Positive and negative pulse trains are generated by positive and negative pulse generators, respectively in response to front and rear edges, respectively of the first rectangular wave and are combined with each other in a first mixer to produce a combined pulse train.

Abstract: A magnetic head includes a magnetic body, at least the permeability or high frequency loss of which is changed with changes of the record magnetic field on a magnetic tape, and a coil. A high frequency signal is supplied to a tuned circuit, which includes the coil and a capacitor, and a signal corresponding to the record magnetic field is taken out through the detection of the changes of the voltage of the high frequency signal supplied to the tuned circuit.

Abstract: Recording apparatus which receives a signal, double-sideband amplitude modulates a carrier with at least three times the highest carrier frequency, with the signal, and records the modulated carrier on a recording medium. The reproducing apparatus reproduces the signal modulated carrier substantially free from superimposed noise and delivers it to an external circuit, where it may be recorded or may be demodulated and the signal recorded.

Abstract: The present disclosure describes an electronic system for use with low cost audio tape recorders whereby a substantially noise-free wide dynamic range is provided for the recording of analog signals in the DC to 30HZ frequency band. In achieving this result, the system utilizes two FM carrier oscillators having center frequencies displaced from each other and modulated respectively in opposite senses by the signal being recorded. The system also provides an additional utility channel of limited dynamic range for the concurrent recording of time markers, digital signals and the like.

Abstract: High resolution video signals of bandwidth up to 25 mHz are recorded magnetically or optically, or are transmitted on a communications channel carrier with superior fidelity by using novel electronic circuit system including implementations of an FM modulator, writing amplifier, and wideband discriminator which enable coding and decoding with high accuracy, low noise, and low interference. The video signals are used to directly modulate a square wave carrier using an FM technique employing a very low center frequency-to-bandwidth ratio without need for subsequent frequency translations. A writing amplifier provides gain needed for saturated recording with unique provisions to balance transition amplitudes for minimum second harmonic distortion without affecting the primary phasing of transitions. A novel multiwinding inductor and pulse discriminator implementation is capable of demodulating the very wide deviation FM signal with good cancellation of the second harmonic and fundamental FM carrier spectrums.

Abstract: In an apparatus for recording a frequency modulated audio signal and a frequency modulated video signal on the frequency multiplex basis onto the same recording track, a muting circuit is necessary so that the reproduced audio signal is not outputted when a dropout takes place and/or when the frequency modulated audio signal is missing on the track. The muting circuit is controlled not only by the output signal of a dropout detector, but by a signal obtained by integrating the dropout detection signal so that the audio output is blocked during a frequent occurrence of dropout. The muting circuit includes a previous value holding circuit serving to hold its output at an input level immediately before the control signal has been given, the previous value holding circuit being arranged in the reproduction audio signal processing system following a demodulator.

Abstract: A magnetic recording and reproducing system is disclosed in which a frequency-modulated input signal is recorded on a magnetic medium together with a further signal which is discriminative from the frequency-modulated signal. The recorded frequency-modulated signal and further signal are frequency-demodulated so that the former reverts to the input signal and the latter represents an FM noise signal which is generated due to the wow and flutter during the recording and/or reproducing process. The extracted noise signal is mixed with the reproduced input signal thereby canceling an FM noise component in this reproduced signal. The mentioned further signal may be an amplitude-modulated signal of or a carrier wave signal for the frequency-modulated input signal.

Abstract: An improved high boost circuit for a reproduced frequency modulated video signal is disclosed, wherein the third harmonic components of the reproduced f.m. video signal is suppressed, so that the undesired so-called over-modulating effect causing signal inversion is avoided at the boundary of different video signal levels.

Abstract: A previous level holding circuit is connected to an output of an FM demodulator to eliminate dropout disturbance from a reproduced audio signal from a record medium on which an FM-modulated audio signal has been recorded. The previous level holding circuit is controlled by an output of a circuit for detecting dropout in the reproduced signal and comprises a gate circuit operable in response to a dropout detection signal and a capacitor. During the occurrence of dropout, the previous level holding circuit holds and produces the reproduced output level assumed immediately before the dropout to eliminate the noise due to the dropout.

Abstract: A method and apparatus for recovering analog signal information from a multiple-track information storage medium such as a magnetic tape is based upon time base error correction of a frequency modulated carrier signal. In one embodiment, the phase difference of a pair of pilot signals recorded on tracks adjacent a data track is compared by a sampling and pulse counting technique to eventually produce a trigger signal for a phase-locked oscillator. The output of the phase-locked oscillator is employed to sample and measure the period of the input data signal. The period values are written as digital values into a digital first-in first-out buffer memory. A stable clock is used to read out the contents of the buffer memory which are thereafter converted to a pulse rate modulated pulse train. The pulse train is converted to a useable analog signal by a pulse rate to frequency converter.

Abstract: The effects of crosstalk of an FM carrier from a first signal channel into a second signal channel are reduced by a variable-frequency notch filter coupled in the second channel. The frequency of the notch in the transmission characteristic of the filter is controlled to track the frequency of the FM carrier. Signals in the second channel at the frequency of the FM carrier are attenuated, and therefore the crosstalk signal is attenuated and its effects reduced.

Abstract: Apparatus is described which is particularly useful for recording pulse signals on a magnetic recording medium. The apparatus includes an amplitude modulator, preferably a balanced modulator, that is supplied with the pulse signal and with a carrier upon which the pulse signal is amplitude-modulated. The pulse signal has gradually rising and falling edges which exhibit a maximum gradient. The modulated carrier is substantially fully suppressed when the maximum gradient of the pulse signal traverses a predetermined level. Preferably, the modulation factor of the amplitude modulator is greater than unity. When used with additional recording apparatus, the balanced modulated signal is filtered by a vestigial sideband filter, and the filtered, balanced modulated signal is frequency-converted to a lower frequency band. The frequency-converted balanced modulated signal is superimposed with an AC bias signal and then recorded.

Abstract: An apparatus for producing a signal which varies as the ratio of the frequency of a first stream to a second stream. In a preferred embodiment of the apparatus, the first stream is transformed into a first signal of value proportional to the frequency of the first stream, and the second stream is transformed into a second signal that has a value proportional to the product of the second stream frequency times a feedback value. The feedback value is derived from a combination of the first and second signals.

Abstract: A video signal processing circuit includes an amplifier with a circuit connected to it to emphasize the amplification of some frequencies relative to others. A non-linear circuit is also connected to the amplifier and comprises a capacitor connected in series with non-linear elements that change the amplification of positive and negative overshoots of the signal relative to the middle amplitude range. The result is non-linear modification of emphasis and can be used to pre-emphasize video signals before using them to modulate the frequency of a carrier and, in the playback section to de-emphasize the signals to minimize FM noise. Use of the capacitor prevents direct current from flowing and thus affecting the threshold levels of the non-linear elements. Component values can be selected to effect temperature compensation.

Abstract: A multitrack recorder is disclosed in which each of a plurality of parallel data signals is mixed with an additional signal corresponding to a digital code indicative of the real time at which the data is received. Each of the mixed signals is then conventionally recorded on a separate track of a suitable record medium. The recorder includes a circuit which shifts the phase of the recorded data signals with respect to each other, while keeping the phase of all recorded time signals in phase with each other. Upon playback, the signals from all tracks are added together. The out-of-phase data signals from each track tend to negate each other and the in-phase time related signals reinforce each other, thus becoming readily detectable. Preferably, the digital time related signals are encoded as two frequencies, both of which are below the band width of the data signals, such that frequency filters may also be employed to enhance the recovery of the time code.

Abstract: In apparatus for recording, or otherwise transmitting, video or other information signals, and in which at least a portion of the signal to be recorded, for example, the luminance component of a color video signal, is frequency modulated and then passed through a filter for limiting the frequency band of the resulting frequency modulated component or signal which is recorded; a signal processor, such as, an automatic gain control or limiter, acts on the frequency modulated output of the filter to eliminate or compensate for amplitude variations that may occur therein by reason of the filter, for example, at portions of the signal where substantial pre-emphasis was applied.

Abstract: Overlapping, minute regions of magnetization in a recording medium, which are produced during recording and cause distortion of the played back signal, are reduced by encoding the signal in a pulse signal. The time between pulses is varied according to the amplitude of the signal to be recorded, and when this pulse signal is recorded, the minute regions are reduced to elemental size. Thus they overlap less and do not distort the reproduced signal by offsetting the zero level.

Abstract: In apparatus for recording and/or reproducing video signals in successive parallel tracks on a record medium, and in which at least a portion of the video signals, for example, the luminance component of color video signals, is recorded as a frequency modulation on a carrier, the carrier of the frequency modulated portion of the video signals, as recorded in tracks that are next adjacent to each other, has different first and second carrier frequencies, respectively, which are in frequency interleaving relation to each other for minimizing cross-talk when reproducing the signals thus recorded. The shifting of the carrier frequency for the frequency modulated luminance component is conveniently achieved by selectively applying different first and second bias voltages to the luminance component as supplied to a frequency modulator, with the difference between such bias voltages being effective in the modulator to establish the desired difference between the carrier frequencies.

Abstract: A playback apparatus for a recorded frequency modulated television signal includes a filter between the record carrier pick-up heads and the limiter-demodulator. The filter characteristics increase the ratio of the carrier signal frequency to the lower side band frequencies in response to a drop in carrier amplitude.

Abstract: Apparatus and method for reducing flutter noise in a frequency-modulated data stream, wherein the data stream is combined with a reference stream which has been modified by the fed-back result of the combination. Before combination, the data stream is transformed into a first rectangular-pulse stream in which amplitude is constant and frequency is dependent on the frequency of modulation of the data stream, whereas the reference stream is transformed into a second rectangular pulse stream of amplitude which is dependent on the fed-back result of the combination of the streams, and the frequency is dependent on the frequency of modulation of the reference stream.

Abstract: A system for reproducing video signals recorded on a magnetic recording medium as a suppressed-carrier modulated signal in which the video information is carried primarily on only one sideband and the frequency of the suppressed carrier is within the band occupied by the video signals prior to modulation. Jitter components in the reproduced signals are substantially cancelled out.

Abstract: A card reader is provided which includes backup means for urging a coded region of a magnetic card against a transducer in a proper orientation and with a proper pressure. The backup means is disposed opposite to the transducer on the other side of a card guide slot, and includes a ball head having a spherical surface which is normally biased by a spring to its operative position extending into the guide slot in which the gap defined between the transducer and the ball head is less than the thickness of a card. As the card is moved through the guide slot, the ball head is moved by the card away from the transducer against the resilience of the spring, but provides a single point backup of the card against the transducer before such movement in the opposite direction occurs.

Abstract: A method and apparatus for suppressing spurious interference components that arise in video recording apparatus of the type which utilize frequency modulation of the carrier signal with a video signal is disclosed. The invention suppresses an unwanted spurious interference signal component substantially to zero by generating the second harmonic of a fundamental signal in the video information modulating signal and adding the second harmonic to the fundamental modulating signal at a predetermined phase and amplitude prior to being modulated upon the carrier signal. The phase is such that the resulting signal is that which, when the second harmonic is added, heightens the upward deviating peaks and flattens the lower peaks of the fundamental modulating signal. The amplitude of the added second harmonic is such as to minimize the interference component and is varied signal in direct proportion to the square of any variation in the modulating index of the fundamental modulating signal.

Abstract: Unauthorized duplication of recorded program material upon magnetic tape, commonly known as tape piracy, is rendered detectable by the present method and apparatus for preparing the program material. The method and apparatus prepare recorded audible program material by eliminating narrow low and high frequency bands of signals from the program material, inserting a preselected low frequency signal in the low frequency band, modulating a predetermined high frequency signal with the low frequency signal, and inserting the modulated high frequency signal in the high frequency band. Subsequent copying of the recorded program material having these inserted signals will introduce a phase shift between the low and high frequency inserted signals.Such a phase shift is detected by a method and apparatus which recover the signal recorded upon the magnetic tape recording suspected to be a duplicate, and filter the recovered signal to detect signals within the high and low frequency bands.

Abstract: An apparatus and method for the frequency modulation and demodulation of a carrier signal by a modulating frequency signal, whereby essentially the same apparatus is used for both functions. During demodulation, the modulating device is switched into a closed loop having a relatively narrow bandwidth, thereby permitting the carrier generated by the modulator to be locked in phase with the signal to be demodulated. During modulation, the loop is opened up and the modulator is used in a normal fashion.