Abstract: A narrow track magnetoresistive transducer has a square shaped bias permanent magnet superposed with an MR element. The square shaped magnet provides bias field components of substantially the same magnitude in both hard and easy axis directions of the MR element. A stable and uniform bias field is thereby obtained.

Abstract: Apparatus and method for phase scatter detection and reduction in a digital signal transmitted over a channel, for example a magnetic recording and reproducing channel. The transmitted signal is equalized to compensate for a non-constant amplitude response and/or non-linear phase response of the channel. A bit synchronization circuit, employing a controllable frequency reference clock signal generator and a digital phase detector, provides a reference clock synchronized with the transmitted data. The amount of phase scatter in the equalized signal is determined by monitoring the switching frequency of the phase detector. The equalizer may be adjusted to minimize that frequency, thereby reducing phase scatter.

Abstract: A transducer and method are described where track width reducing notches are filled with a nonmagnetic material which is heated to or slightly over its softening temperature but below its melting temperature. Concentrated high pressure at discrete locations is applied to the softened nonmagnetic material to enhance flow thereof into the notches.

Abstract: An improved clock recovery system for use in digital rotary scan magnetic playback devices utilizing a phase locked loop. The clock signal recovered from the playback data has a phase error with a periodic component caused by time base variations in the playback data and a random noise component due to playback channel noise. The phase locked loop of the invention tracks the periodic component, while it suppresses the random noise component. The improved system is suitable for tracking wide bandwidth dynamic time base variations in the playback data without introducing phase errors caused by random noise into the recovered clock signal.

Abstract: A plurality of magnetic blocks is integrally joined side-by-side with a nonmagnetic material therebetween to provide a monolithic block defining parallel transducing gap planes, each pertaining to one multichannel transducer stack. A plurality of first parallel slots in the monolithic block intersects the gap planes to define a plurality of partitions, each partition forming pairs of magnetic pole pieces defining respective transducing gaps pertaining to respective stacks. The transducing gaps of each partition define interlaced transducing channels of the multichannel assembly. Second parallel slots provided along the gap planes have apexes defining transducing gap depths. The resulting transducing channels have uniform gap azimuth and gap depth while uniform internal stack alignment between all the respective stacks is obtained.

Abstract: Plated magnetic recording material, such as magnetic tape, composed of a thin layer of ferromagnetic metal and a base film layer are made by plating a passivated smooth continuous surface such as the surface of a cylindrical mandrel or an endless belt with a plate of ferromagnetic metal, applying the base film layer to the plated surface, and stripping the resulting laminated composite from the surface. The smoothness of the surface of the ferromagnetic metal layer depends on the smoothness of the continuous surface rather than on the smoothness of the surface of the base film stock.

Abstract: The changing diameters of the respective tape packs wound on the supply and take-up reel are continually measured. The measured diameters of each reel are compared to a stored minimum diameter value corresponding to an end of tape on that particular reel. When the apparatus is in a learning mode, the stored minimum diameter values for each reel are updated every time when a new measured value is smaller than the previously stored value. The last stored value is utilized for comparison in an end of tape detection mode, to allow stopping the tape transport mechanism before the end of tape would run off that reel to prevent damaging the transducers or the tape.

Abstract: An improved voltage controlled amplifier employing an operational transconductance amplifier which is temperature independent and offering an improved dynamic range for the input signal is disclosed. An operational amplifier configured in the inverting mode is used as an input device having a first operational transconductance amplifier in the feedback path as a gain control element. The output of the operational amplifier provides a control voltage to effectively drive a second operational transconductance amplifier.

Abstract: A parity and/or syndrome generator generates a block parity check for the detection and/or correction of errors in a multi-channel digital data communication system using a linear code or a coset of such code in which data and parity bytes are intended to be digitally encoded in n by m bit data blocks to form a respective codeword in n parallel bytes of m bits in serial order of significance in the form of a codeword having n elements represented by respective bytes in the Galois field GF(2.sup.m), such Galois field being defined by an m-order field generator polynomial in integral powers of z between z.sup.0 and z.sup.m, where z is the inverse of the delay operator z.sup.-1 of such Galois field. A first circuit produces a first partial parity check for the bit of such significance in each of the n elements of the respective codeword. A second circuit sums in the Galois field over all elements of the codeword the first partial parity checks to form a second partial parity check.

Abstract: In the preferred embodiment of the high density multichannel transducer each channel has two assembled corresponding magnetic core portions, each portion having an intermediate and a rear leg portion, respectively. Both core portions are contiguous with a magnetic pole and each provides a separate flux path. The rear leg portion extends at an acute angle to the intermediate leg portion and it converges towards the transducing gap plane. A recording coil is placed on the intermediate leg portion. The angle of the rear leg portion is selected such that sufficient clearance is provided from the intermediate leg portion to allow winding the reproducing coil directly around the rear leg portion. Interchannel crosstalk is reduced and mechanical damage to the reproducing coil is eliminated.

Abstract: A magnetic tape timer and method wherein the measured tape time as well as stored cue markers are not affected upon receiving a preset or reset signal. An offset signal is generated and stored as a difference between the preset or reset signal and a tape time which is coincident with receiving the preset or reset signal. The tape time, cue markers and other tape time related values are then modified by the offset signal for further use such as for display.

Abstract: A programmable time code generator utilizes a synchronous parallel-to-serial data converter for conversion of time code in parallel form into serial form. The resulting longitudinal time code is suitable for recording on magnetic tape in synchronism with an information signal. The time code generator can be readily adapted for various video recording formats, such as NTSC, PAL, PAL-M, SECAM, etc., as well as for synchronous time code generation in other types of recording. In addition, the frequency of the generated longitudinal time code can be changed in a simple manner to be adapted for recording at various tape speeds which are different from the normal playback speed.

Abstract: The clock signal to a fine delay shift register is divided by the number of fine delay bits for application to a coarse delay shift register such that two serially connected shift registers can provide a range of delays equivalent to a shift register having a number of bits equal to the product of the bits of the two shift registers.

Abstract: A timing error between consecutive tracks of reproduced data from a rotary scan recording/reproducing device is detected as a difference between a normal and actual occurrence of a synchronization signal. A correction signal is provided to reduce the timing error and it is stored, updated and utilized to offset a bit counter synchronous with the reproduced data in the absence of the synchronization signal. The effect of short term dynamic errors is reduced by accumulating occurrences of the timing error in the same direction and updating the stored correction signal only when a predetermined number of occurrences in one direction is obtained.

Abstract: A magnetic transducer assembly having separate core portions with keyways provided therein. The core portions are assembled to form a substantially closed magnetic circuit defining a transducing gap. The keyways form recesses which are contiguous with a transducer inner space provided by the assembled cores. The inner space and recesses are filled with a non-magnetic bonding material. The resulting bond improves the mechanical coupling between the core portions.

Abstract: High speed serial data bits of a data stream are received, stored, shifted and compared in parallel to bit contents of a known correlation word. For each bit match a known signal change is provided on a common terminal. High speed current or voltage changes on the common terminal are proportional to the number of matching bits and are monitored to detect presence of the correlation word in the received data stream. The circuit has minimum number of components and built-in temperature compensation.

Abstract: A method and apparatus are disclosed for eliminating or dropping digital samples from a data stream of samples to reduce the data rate for transmission of the data stream through a transmission channel, such as a data record and reproduce system or the like, and for subsequently reconstructing the original data stream by using the unaltered and recovered digital samples to generate an interpolated value for each of the samples that has been dropped. A finite impulse response multi-term digital filter is used to generate the interpolated value for the samples that have been dropped. Advantages reside in the fact that errors are not propagated during multiple generation recording or transmission, since unaltered sample values are always used to produce the interpolated value for the dropped sample that is being reconstructed. The invention has particular use in video recording and reproducing wherein it is desirable to record a digital data stream at the lowest practicable data rate.

Abstract: A method and apparatus are disclosed for enabling the continuous monitoring of recording circuit performance and the automatic optimization of the recording process in a rotary head recorder having a plurality of recording heads. A calibration signal is recorded by each recording head onto the overlap area of a moving magnetic tape medium. A fixed monitor head subsequently detects components of the recorded signal, the magnitudes of which are squared and retained in sample and hold units. The sampled and held values are periodically used to construct an outputted value commensurate with recording circuit performance. Optimization is accomplished by varying the recording drive level of a recording head about a predetermined point during a series of successive overlap periods. A DC error voltage is derived from the respective outputs resulting from such variation, and used to shift the recording drive level of that head towards a point of optimum playback output.

Abstract: A constant current source is combined with a fixed AC bias circuit to supply a constant current biased drive signal to a control track, an audio, etc., record head. A voltage doubler bridge configuration may be used to double the current to the head.

Abstract: A method and apparatus are disclosed for performing a reduction of the data rate of a data stream for transmission through a transmission channel or recording and for subsequently reconstructing the original data stream upon receipt or during reproducing. The method and apparatus utilizes a combination of two processes, one of which eliminates or drops digital samples from the data stream to reduce the data rate for transmission and which subsequently reconstructs the original data stream using the unaltered and recovered digital samples to generate an interpolated value for each of the samples that had been dropped. The second process utilizes differential pulse code modulation for reducing the number of data bits per sample before sending the data stream through the transmission channel and for subsequently restoring the data to its original multi-bit form.