Abstract: A plural channel playback system comprising magnetic recording tape movable past a reproducing transducer head having at least one transducing element for each track is shown together with skew detecting means. At least two of the tracks are recorded with digital data signals comprising equal length data words with a parity bit, with the parity bits being simultaneously recorded along the tracks. Parity bit lock-on circuits are responsive to outputs from two tracks, which lock-on circuits generate word clock pulses in synchronization with the recorded parity bit signals. A phase detector responsive to word clock pulses from the parity bit lock-on circuits produces an error signal output proportional to the phase difference between said word clock pulse inputs thereto, which error signal is related to skew. The azimuthal position of the reproducing head relative to the recording tape is adjusted either manually or automatically to minimize the error signal.

Abstract: A velocity error compensator adapted for use in a time base corrector of the type which includes a main memory into which individual periods, such as horizontal line intervals, of information signals, such as video signals, are written at a write-in rate synchronized with the information signals, and from which the individual periods of information signals are read out at a reference read-out rate. The velocity error compensator includes a storage device for storing velocity error signals associated with corresponding ones of the periods of information signals. The velocity error signal associated with the period of information signals then read out from the main memory, and also the velocity error signals associated with the preceding and next-following periods of information signals are simultaneously read out from the storage device. These three velocity error signals are combined to produce a velocity error correction signal which is used to modulate the information signal read-out rate.

Abstract: A multiple track tape recording system as disclosed in which the data recorded in each track is coded to allow for error correction and skew correction. The skew correction is done with a code which also can be used for error correction. Thus the system overhead required for skew and error correction is reduced. The data in each tape track is first divided into data blocks of equal length. An error-correcting parity word is computed from the data bits in the data block and appended to each data block to form a code word.During the decoding operation, each tape track is fed through a first-in, first-out buffer memory (FIFO) and examined for valid code words. When a code word is detected the output of the FIFO for that track is stopped. After code words have been detected on all tracks the FIFO's are started in synchronisms, thus correcting for skew and synchronization errors.The code also allows for detection of both random and burst errors on each of the multiple recorded tracks.

Abstract: Time base errors in PAL subcarrier reference bursts, created in part by the operation of a video tape recorder, are detected by the recorder and used for detecting the phase shift error in PAL phase angle switching between bursts on adjacent video signal lines which existed before the video signal was recorded. The video tape recorder timing errors detected on the PAL bursts are first detected after the 90.degree. phase angle between successive PAL bursts has been eliminated. Two sample and hold units then are alternately strobed, each at a point in time during a given tape recorder head pass wherein the error signals are normally most accurate, such that a first burst timing error is retained in one such unit and a next burst timing error is retained in said second unit. The outputs of these two sample and hold units are filtered and combined in an integrator for generating a voltage control signal whose amplitude varies as a function of the pre-existing burst shift error.

Abstract: The present invention provides apparatus for calculating the skew distortion introduced in each channel of a multi-channel longitudinal recorder when recorded information signals in at least two channels contain a detectable characteristic. In accordance with the invention, a timing signal is recorded containing certain information that is used, upon playback, to produce a reference marker which is compared with the detectable characteristics of recorded information signals to produce a measure of skew distortion.

Abstract: Audio signals with opposite relative phases are recorded on two tracks. A dual track head reproduces the signals from the two tracks and introduces another phase reversal of one signal relative to the other. Noise which was not present in the record circuit, but enters the system at the playback head, is out of phase in the signals which the playback head applies to the playback circuit. Combining the out-of-phase noise components of the two signals substantially cancels the noise.

Abstract: The present invention provides apparatus for adjusting the time base of a signal that is read out from an addressable memory device. In accordance with a disclosed embodiment, coarse time base adjustment is provided by controlling the address count produced by a readout counter, while the phase of the counter clocking signal is adjusted to provide fine time base adjustment.

Abstract: A method and apparatus is disclosed for obtaining second order velocity error correction signals for use in a time base corrector that removes instabilities in a video information signal reproduced from a magnetic medium. The apparatus utilizes the phase of the color burst component of the video information signal from successive horizontal lines to determine the change in velocity error. The change in the phase of the burst components of successive horizontal lines is first used to generate a first order or straight line approximation of the velocity error, and the difference between successive changes in burst phase, from which two successive first order error approximations are generated, is used to determine the approximate rate of change of velocity error.

Abstract: A system is disclosed for arranging digital data provided in a plurality of individual information channels. The digital data provided in each channel includes a continuous serial stream of digital data bits having synchronizing signals periodically included therein. All of the channels include a like number of data bits between successive synchronizing signals. Also the data in each of the individual information channels may be skewed in time with respect to corresponding portions of the data in the other information channels. A plurality of processors are provided with each being associated with a corresponding channel and each including a storage device together with means for sensing the occurrence of a synchronizing signal in the corresponding channel together with apparatus for storing data bits in selected positions in the storage means in accordance with the position that the data bits have in the serial stream with respect to the synchronizing signals.

Abstract: A video tape recording apparatus with the use of an Hadamard transformation system is disclosed. The apparatus comprises means for distributing the video signal to a plurality of channels, means for recording and reproducing the distributed video signals by plurality of magnetic heads, means for synchronizing a time-base correction signal for time-base correction with a sampling signal for Hadamard transformation, and means for phase-controlling a sampling signal for Hadamard inverse transformation to the time-base correction signal in phase.

Abstract: A balancing apparatus particularly useful in a quadrature magnetic head pickup device employs separate amplitude and phase detecting circuitry. A phase detector provides a DC level indicative of a phase variation between a reference signal and a random signal to be compensated. A DC signal is provided which then causes a phase shifter to provide a square wave output indicative of a phase lag or lead, which phase signal is of a magnitude to compensate for the phase angle error of the random signal. An amplitude detector compares the amplitude of the random signal with a predetermined reference signal to provide another DC voltage signal indicative of the amplitude offset. The generated phase and amplitude signals are combined in a summing amplifier to provide an output signal which is fed back to the drive circuitry associated with a magnetic head to compensate for the random signal over a wide range of temperatures.

Abstract: A system is disclosed wherein a series bit stream of digital data, at a relatively high bit rate, is received and the data is recorded on a multiple channel recording medium. During the recording of the data, the data is divided into frames of words each having N bits. Each word has a parity bit added so that each word has N+1 bits. In addition, the data for each channel is recorded in frames where each frame includes a synchronization word followed by fixed plurality of data words. Since each recorded frame includes more bits than the originally received data bits per frame, the recording bit rate for each channel is substantially higher than the incoming data bit rate per channel. All frames from the various channels are recorded simultaneously so that the synchronization words from channel to channel are in alignment. During the read-out process, all of the channels are simultaneously read so as to provide a plurality of reconstructed data channels, each including a serial stream of data bits.

Abstract: Apparatus for correcting time base error (such as flutter, scatter, and skew) in a multichannel, sampled-analog type video signal includes means for clocking the signal portions carried by respective channels into respective deflutter buffers by respective input clock signals derived from horizontal sync information appearing in respective channels. Each buffer contains input register means capable of receiving a signal portion containing flutter distortion, storage means for holding the signal portion received, and output register means for delivering the signal at a substantially constant periodic rate. The input register means is controlled by the input clock signal, which contains flutter distortion corresponding to the flutter distortion in the signal portion.

Abstract: An electronically controlled magnetic recorder for rapidly optically scanning an original document and for producing a latent magnetic image thereof. The recorder comprises directly coupled helical optical scanning and helical magnetic writing.

Abstract: A multiple bit deskew buffer while providing skew correction for multi-track data read on mass storage devices is disclosed. All data transfers are synchronized to one basic clock eliminating the multiple clocking systems utilized in the prior art. The invention is arranged such that it could be easily modified so as to vary the number of bytes of data held in the byte buffer by either hardware, firmware, or software means.

Abstract: A digital data recovery apparatus for extracting phase encoded data from mass storage devices is disclosed. By selective strobing of the data string at a frequency determined by the incoming data rate of data already read, a continuously updated data "window" is generated. The data synchronization, clock control and frequency averaging of the previously read data is accomplished without the use of any analog circuitry.

Abstract: A system for accurately merging data signals generated by two spaced apart multi-element MICR read heads is provided. Digital data signals are sampled near the signal peaks, converted to NRZ (non-return-to-zero) data and synchronized to a common fixed frequency. The digital data signals then are serialized to form two digital data streams, each of which corresponds to the responses of one of the two read heads. Phase differences between the two data streams are detected and corrected. In accordance with the invention, the data streams are interlaced to form a single digital data stream accurately representative of the information field sensed by the MICR read heads.

Abstract: A digital circuit and method for measuring magnetic tape skew of magnetic tape units by recording on two channels of a reference tape a digital bit pattern of alternate pairs of zeros and ones.Digital logic circuitry, which detects this information on a reference tape when read from a magnetic tape unit to be tested, feeds the digital information on one channel to a shift register which is sampled by a clocking signal derived from the other channel. The digital bit pattern indicated at the output stages of the shift register will identify the existance of any excessive lag or lead skew.

Abstract: A test set is disclosed for measuring read/write head skew in a magnetic tape recording system. Read head skew is measured by reading a reference tape having substantially identical alternating signals recorded in all tracks thereof and measuring the time between the receipt of signal peaks of corresponding portions of the signals read from any two tracks of the reference tape. Pulses from a high frequency oscillator are counted during the time between the signal peaks to obtain counts which are representative of the read head skew. These counts are averaged over a number of cycles of the alternating signals and displayed on a digital display. Write head skew is measured by writing an alternating signal onto two tracks of a magnetic tape and reading the two tracks with a properly aligned read head.

Abstract: The invention disclosed reduces unrecoverable read errors from a magnetic tape resulting from the apparent lack of a cyclic check character (CCC), sometimes referred to as a cyclic redundancy check character, or a longitudinal check character (LCC), sometimes referred to as a longitudinal redundancy check character. The detector provides a variable read window to synchronize receipt of the CCC and/or LCC with their associated data blocks even though the CCC and/or LCC was not written in the appropriate time frame called for by the write specification of the tape in question.

Abstract: In one exemplary embodiment, an improved apparatus for recovery of a dead track in NRZI tape data format having parallel transmission of data bits is provided in which a dead track recoverer circuit is provided for sensing the absence of a necessary data bit to replace the dead track data bit, and provides means for inserting the data bit in proper time sequence with the data character to reconstitute the data character and thus recover the data information, even though one channel may be dead or inoperative. In combination with the dead track recovery circuit is an improved clock track generator which electronically simulates a clock track to generate strobe signals by utilizing the bit scatter average of the bit characters, averaging them over several characters and generating a variable periodic clock that generates strobe signals having a delay of one-half cell time between data characters.

Abstract: This invention discloses a multi-track recorded information regenerating system which regenerates signals recorded on a plurality of tracks and which composes and demodulates these recorded signals so as to obtain a read output signal. The characteristic feature of the present invention is to provide a delay circuit, which delays the regenerated signals in each track. Three signals are synthesized; that is, a first signal is synthesized from two regenerated signals from two tracks, and a second and a third signal are synthesized from one of the regenerated signals from two tracks and one of the outputs of the delay circuit. These synthesized signals are detected by an error checking circuit to determine whether or not said synthesized signals represent correct information recorded on the magnetic track, and the synthesized signal having the correct information is used as the read output of the multi-track recording system.

Abstract: In last line velocity compensation of color television signals reproduced by video recorders, the velocity error signal for the next to last line of information before the head switch that occurs during the vertical blanking interval is stored for a time extending beyond the period of the last line. The switching between transducers that occurs during each vertical blanking interval is delayed so that a color burst signal following the last line is reproduced and a velocity error for the last line generated. This last line velocity error signal is differentially compared with the stored next to last line velocity error to provide a velocity error difference signal. The error difference signal is stored for the period between the foregoing and succeeding vertical blanking intervals.

Abstract: A network is disclosed for automatically checking the skew and character spacing of digital tape drive systems to indicate out-of-tolerance conditions of those parameters. The network enables a tape drive to check its own recording accuracy as well as that of tapes recorded on other drives. In operation, the first detected pulse of each character triggers a monostable multi-vibrator which locks out further data pulses and initiates a window pulse equal in length to the maximum permissible skew. At the end of the window pulse data pulses may again be received. If a pulse is received after termination of the window pulse, the skew is determined to exceed specifications and a skew error indication is given by the illumination of a display light, for example. A similar circuit arrangement is provided for detecting character spacing which is less than the minimum required for unambiguous data reproduction.