Abstract: A system may include a Class-D stage comprising a first high-side switch coupled between a supply voltage and a first output terminal of the Class-D stage, a second high-side switch coupled between the supply voltage and a second output terminal of the Class-D stage, a first low-side switch coupled between a ground voltage and the first output terminal, and a second low-side switch coupled between the ground voltage and the second output terminal. The system may also include current sensing circuitry comprising a sense resistor, such that an output current through a load coupled between the first output terminal and the second output terminal causes a first sense voltage proportional to the output current across the sense resistor.

Abstract: A signal recovery circuit includes, a voltage controlled oscillator that generate a clock signal, a phase frequency comparison circuit that compares phases of the clock signal and an received input signal and compares frequencies of the clock signal and the received input signal, a voltage adjustment circuit that adjusts the phase of the clock signal by adjusting control voltage of the voltage controlled oscillator based on an output of the phase frequency comparison circuit, and a control circuit that acquires an amplitude of the received input signal, detects continuation of the same sign in the received input signal based on the acquired amplitude, stops an adjustment of the phase of the clock signal generated by the voltage controlled oscillator when the continuation of the same sign is detected, and executes adjustment of the phase of the clock signal when the continuation of the same sign is stopped.

Abstract: A common-key blockcipher processing structure that makes analysis of key more difficult and enhances security and implementation efficiency is realized. In a key scheduling part in an encryption processing apparatus that performs common-key blockcipher processing, a secret key is input to an encryption function including a round function employed in an encryption processing part to generate an intermediate key, and the result of performing bijective transformation based on the intermediate key, the secret key, and the like and the result of performing an exclusive-OR operation on the bijective-transformed data are applied to round keys. With this structure, generation of round keys based on the intermediate key generated using the encryption function whose security has been ensured is performed, thereby making it possible to make analysis of the keys more difficult. The structure of the key scheduling part can be simplified, thereby making it possible to improve the implementation efficiency.

Abstract: An encryption device and method and decryption device and method which implement a bit-based encryption scheme and hardware design. The encryption device includes a random number generator, receiving a main key, determining a working key using at least one random number and outputting a working key, a model, receiving the main key, the working key and plain text to be encoded and generating at least two frequency counts. The encryption device further includes an encoder, which outputs encoded text based on the working key, the plain text and the at least two frequency counts. The encryption device and method and decryption device and method process encrypted text that is based upon a stream structure with an unlimited key length and may be compressed by 50%. The encoded text is changeable with different environments even for the same plain text and the same key. Operations of the hardware design are based on arithmetic additions and shifts, and not multiplications and divisions.

Abstract: Accordingly, an improved method for recording data on an optical medium is disclosed which includes receiving and encoding a first set of data frames by a CIRC encoder to generate a second set of data frames. A control byte is then added to each of the second set of data frames to generate a third set of data frames. The third plurality of frames of data are received and encoded at an EFM encoder to generate a section comprising a plurality of Channel frames. The control byte of a sequentially first one of the third set of data frames is replaced with a SYNC 0′ byte selected from the limited group of previously unassigned fourteen-bit combinations. The control byte of a sequentially second one of the third set of data frames is also replaced with a SYNC 1′ byte selected from the same group.

Abstract: The video signal reproduction apparatus having two kinds of equalizing circuits to correct the level of a frequency-modulated luminance signal, that is, a first equalizing circuit which raises the level of the upper sideband range of the frequency-modulated luminance signal and a second equalizing circuit which raises the level of the lower sideband range of the frequency-modulated luminance signal, so that the part of the frequency-modulated luminance signal where a horizontal synchronizing signal is not modulated is processed by the first equalizing circuit, while the part of the frequency-modulated luminance signal where a horizontal synchronizing signal is modulated is processed by the second equalizing circuit.

Abstract: The present invention relates to a method and device for recording the low frequency band of an audio signal on an amplitude modulated carrier above the highest frequency component of the audio signal. The carrier frequency is at least 19 kHz and is recorded at an adequate level above the noise floor typically about 10 to 30 dB below peak level. The audio signal with the low frequency band optionally attenuated or omitted is directly recorded in the normal audio region on the same track with the corresponding AM carrier. During playback the amplitude modulated carrier is recovered using a highpass or bandpass filter, demodulated and the low frequency signals mixed with the audio. When applied to audio tape reproduction, the present invention improves bass response as compared to direct recording alone. High quality low noise tape and narrow bandwidth of the AM signal allows audio reproduction with high signal to noise ratio.

Abstract: An apparatus for reproducing from a recording medium a frequency-modulated audio signal which has its carrier level in a specific period determined according to the kind of information and for producing the audio signal after processing the reproduced audio signal is arranged to control the signal processing action according to the output of a detecting circuit which detects the level of a difference between the carrier level of the frequency-modulated audio signal obtained in the specific period and the carrier level obtained in a period other than the specific period or detects changes taking place in the carrier level. This arrangement enables the apparatus to process the audio signal appositely to the kind of the frequency-modulated signal thereof without recourse to any additional reproducing circuit solely for this purpose. Further, the apparatus is arranged to prevent any faulty signal processing action by nullifying as necessary the output of the detecting circuit.

Abstract: An information recording system and apparatus records on a recording medium an audio signal, which is time-base compressed at a predetermined compression ratio, together with a data signal indicative of the compression ratio. A start signal indicative of the start of the audio signal, the data signal, the audio signal and an end signal indicative of the end of the audio signal are recorded in this order. A recording medium recorded by such system and apparatus is disclosed. A reproduction apparatus is also disclosed which reproduces the information out of such recording medium.

Abstract: A video signal recording and playback apparatus and method which is applicable to wide-band recording in which a video signal is divided into a plurality of channels by time-axis expansion, and the channels are recorded in parallel on respective tracks. Prior to recording, a reference signal consisting of a plurality of different signal bursts, each having a specific frequency and each being superimposed on a specific DC level, is inserted into blanking intervals of the video signal and recorded therewith. On playback, the amplitudes of the signal bursts in the reference signal are monitored, and playback equalizers are controlled accordingly such as to maintain a predetermined equalizer characteristic and to maintain identical overall frequency characteristics for the various channels.

Abstract: A magnetic disc reproducing apparatus for reproducing analog or digital information signals selectively recorded in a plurality of tracks of a magnetic disc includes a transducer placed in transducing relation with the plurality of tracks for reproducing the information signals recorded in one of the tracks, a checking circuit connected to the transducer for checking a portion of the reproduced information signals and an identifying circuit connected to the checking circuit for identifying whether analog or digital information signals are being reproduced.

Abstract: Apparatus for correcting the distortion in the output of a playback device introduced by wow and flutter by sampling a constant frequency as reproduced and comparing it with the signal as originally recorded to produce a correction signal for modulating a delay device coupled to the output of the playback device.

Abstract: A method and apparatus for recording a data signal and for playing it back at a variable speed ratio including a recording unit, a playback unit and a speed control unit. A modulated carrier wave is first recorded and subsequently played back at a different speed from the recorded speed. A recording speed control signal controls the recording speed through the speed control unit, and a part of the speed control signal is recorded simultaneously with a data signal from a miniature test model on a record medium, such as a magnetic tape, by a write unit, such as a recording head, after being operated on by the data signal. The playback speed is controlled by a playback speed control signal at a variable speed ratio, so that it is possible to achieve any speed ratio, such as .sqroot.10, etc., between the recording speed and the playback speed.

Abstract: At least one channel of digitized information is recorded in a selected number of data tracks by a record medium. The digitized information is encoded, modulated and then recorded in a predetermined number of tracks. For example, if n channels of digitized information are to be recorded in m data tracks, then each channel is recorded in m/n data tracks (m.gtoreq.n). A control signal is generated to include control data representing at least one of the following: (a) the number of data tracks in which each channel of digitized information is recorded, (b) the encoding scheme used to encode the information, (c) the type of modulation used to modulate the encoded information and (d) the relative speed of movement of the record medium. The control signal is recorded in a separate control track. Thus, the control signal represents the particular format in which the digitized information is recorded.

Abstract: A system for reproducing and/or transmitting analog audio information is disclosed which provides for the correction of time base errors. An inaudible pilot signal accompanies the audio information. Correction circuitry examines the frequency and phase characteristics of the pilot signal to develop signals for effecting correction of the errors.

Abstract: An apparatus for recording and detecting a cue signal which comprises:a recording section (100) for recording in a recording medium a composite cue signal formed of a component signal having a first frequency (f1) and denoting a tape speed pattern and another immediately following component signal having a second frequency (f2) and representing a cue signal pattern; anda detecting section (200), which, at the time of reproducing said composite cue signal, compensates a component signal which represents a cue signal pattern and is detected immediately after a tape speed pattern component signal drawn out of the recording medium in proportion to the period (T10) of said tape speed component signal, andwhen said composite cue signal is recorded in said recording medium, provides data on a cue signal pattern on the basis of the compensated component signal denoting a cue signal pattern.

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: The demodulator is especially adapted for a data signal (F'c) that was recorded on tape in the form of a frequency modulated signal together with a reference signal (F'R) of frequency greater than the greatest frequency of the data signal, so that both signals are subject to the same proportional frequency errors. During each cycle of the data signal, a representation of the period of one cycle of the reference signal is measured and stored. Then at the end of each following cycle of the data signal, there is produced a pulse of area dependent on the representation. A filter (LPF) produces a signal representing the area of each pulse averaged over one cycle of the data signal.

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: A method and apparatus for the recording and reproduction of an audio signal for multi-channel play-back in which both a monaural signal and a code signal are recorded on a magnetic tape, the recorded code signal having characteristics in accordance with the selective feeding of the audio signal to the various channels together with an adjusting device through which the code signal is controlled to thereby control the distribution of the audio signal throughout the multi-channel reproduction apparatus during multi-channel reproduction of the audio signal.

Abstract: An improved method and apparatus for reducing wow and flutter associated with recording devices are disclosed. Two input signals containing useful information and a constant reference signal are recorded and reproduced by a three channel recording and reproducing system. The reproduced signals contain, in addition to the recorded signals, frequency deviations caused by wow and flutter of the recording and reproducing system. Reproduced signals are converted to frequency-dependent voltages and the constant reference signal is subtracted from the reproduced reference voltage to provide a reference error voltage. The reference error voltge is transmitted to a multi-state control circuit in which the reference error voltage cancels the error voltage components of the two reproduced information frequency-dependent voltages leaving only the frequency-dependent information input signal voltages which are then transformed into frequency signals substantially equal to the recorded information signals.

Abstract: In apparatus for reproducing a signal recorded on a magnetic tape or other record medium and which includes a signal band containing an information signal, such as the chrominance component of a color video signal, and a reference signal of a predetermined frequency occurring only during spaced intervals, such as, the burst signal; the mentioned band of the reproduced signal is applied to a variable gain amplifier for controlling the level of the chrominance component, a burst gate receives the level-controlled output of the amplifier and is gated during the intervals of the burst signal to provide an output during each such interval, a crystal filter tuned to the frequency of the burst signal receives the output of the burst gate so as to pass only the burst signal, and the gain of the variable gain amplifier is controlled in accordance with the combined levels of the outputs of the burst gate and the crystal filter, respectively.

Abstract: A magnetic recorder employs a feedback phase equalizer for adjusting the readback signal to enhance detection capability. Phase errors are measured and used as criteria for dynamically and adaptively adjusting phase compensation of the read-back signal. In a preferred form, averaging phase errors over a predetermined signal characteristic of the readback signal controls adjustment of phase equalization.

Abstract: A digital flutter reduction system which corrects for a varying time base ror in FM recordings on magnetic tape. Pulse transitions from the outputs of a reference oscillator and a reference tone on a first tape track are compared by a flip-flop whose output is a pulse having a width corresponding to the time base error. The output pulse enables a first counter to provide a digital output which is loaded into a second counter. Pulse transitions from a second tape track containing recorded data advance the second counter over a number of counts indicative of a correction factor. The pulse transitions of the recorded data are delayed in accordance with the correction factor thereby reducing the time base error.