Abstract:
A method of demultiplexing a composite signal (c) containing a plurality of data streams (a, b), each stream being coded in a polarised code and phase shifted from other data streams by a predetermined phase shift comprises: providing a correlator signal (d, f) for each data stream (a, b), each correlator signal being mutually orthogonal with the or each other correlator signal and phase shifted from the other correlator signals by the predetermined phase shift of its corresponding data stream, and separately multiplying the composite signal by each correlator signal to derive resultant signals (e, g) each representing the data bits in a respective one of the data streams. There is also provided an apparatus for carrying out this method.
Abstract:
A wave-shaping circuit which comprises a comparator (12) for comparing the level of a signal reproduced from a magnetic tape on which, for example, PCM signals are recorded with the level of a reference signal, and a D flip-flop circuit (26) for holding an output signal from the comparator for a prescribed period. Where the reproduced signal has a higher level than the original level of the reference signal, then the reference signal is made to have a higher level than the original level by an output signal from the D flip-flop circuit (26), that is, an output signal from the comparator (12). Where the reproduced signal has a lower level than the original level of a reference signal, then the reference signal is made to have a lower level than the original level by the output signal from the comparator (12). As a result, strains occurring at the high density recording are not reproduced.
Abstract:
A PCM signal processor having a signal input terminal which receives a PCM data signal from a PCM data signal reproducing apparatus such as a VTR (18R), a memory (14) for storing the PCM data signal, a standardized signal input terminal for providing a standardized signal corresponding to a synchronizing signal for synchronizing the VTR (18P), an address counter (38) for designating the address of the memory (14) which is to be read, and means for providing the address counter (38) with preset data in response to the standardized signal.
Abstract:
A pulse code modulation (PCM) signal recording system includes a first signal processor (1 to 7) for processing a recording signal into a predetermined PCM signal, a second signal processor (18 to 24) for processing a reproduced PCM signal into a recording signal, a first clock signal generator (9) generating a master clock signal, a second clock signal generator (12 to 14) generating at least one recording clock signal from the master clock signal, the recording clock signal being supplied to the first signal processor (1 to 7), a third clock signal generator (27) generating at least one reproducing clock signal from the master clock signal, the reproducing clock signal being supplied to the second signal processor (18 to 24), a comparator (32) digitally comparing the phases of the second and third clock signals and producing a control signal, and a controller (29) receiving the control signal and controlling the second or third clock signal so that they are synchronized.
Abstract:
To provide for a more economic buffer capacity through facilitating high speed readback check of data transferred to a cyclic memory (16) from a free input buffer before the source data is lost, the cyclic memory is organized into a number of data blocks, each interleaved with or simultaneously accessible with the other data blocks. Thus, a long data record comprises several data blocks and therefore several cycles of the memory. A readback check of data transferred is accomplished by writing data into one check number generator (51) and one data block in a first cycle, writing data into another block on the second cycle while reading back the first data block to a second check number generator (52), continuing in this manner until the entire record is transferred, and reading the last block of written data into the check number generator (52). The two generated check numbers are then compared to detect any error and effect a retransfer if required before the source of the record is lost by overwriting.
Abstract:
A synchronizing system for the control of the transmission of digital information which is composed of blocks separated by gaps and for which synchronization requires the production of a reference pulse. Each field of information includes a series of spaced coded synchronizing control words each of which is a coded representation of the separation between the word and the position required for the synchronizing signal. The synchronizer (FIG. 3) includes a decoder composed of read-only memories (IC2, IC3) which can set a counter (IC4, IC5 and IC6) in accordance with the separation. The decoded synchronizing control signal is compared by comparator IC8 and a read-only memory IC7 with the instantaneous contents of the counter and the counter is adjusted only if parity is not detected. If parity is detected and continues to be detected for each synchronizing control word, the counter counts towards a datum whereupon the synchronizing signal is produced. The occasions of parity are counted by another counter which causes the production of an inhibiting signal for the output synchronizing signal unless a predetermined number of occasions of parity are counted.
Abstract:
An improved method and apparatus for maintaining a recording head (26) in an optical recording system at a constant linear velocity relative to a rotatable disk support (10), a rotation controller (40) uses a cumulative measure of rotation to determine an angular velocity of the rotating disk support (10) necessary to maintain a constant linear velocity.
Abstract:
Inserting operational data onto a magnetic disk allows information to be transferred from a servowriter station (50) to a verifier station (60). This operational data allows disk specific operational data to follow the disk without separate means for attaching data to each disk. The servowriters, which cannot write information to disks at the data sector frequency, insert the operational data into selected greycodes in the servo sectors. When the disks are verified, the operational data may be moved from the servo sectors to the data sector in the Z-tracks for more permanent storage.
Abstract:
A disk can store data from two different operating systems, particularly DOS and MAC OS formats. The initial sector on the disk, sector zero (12), is divided between the operating systems (102, 104, 106), allowing two sector signatures. As a result, DOS recognizes the disk as valid and the MAC OS can support a driver on the disk. According to another aspect of the invention, the DOS portion of the dual-format disk (20) is reclaimed by having a software program start its execution on the dual-format disk then switch its execution to another storage device. As a result, the program can dismount the dual-format disk and safely reclaim it for use on the MAC OS.
Abstract:
A combination is disclosed of a magnetic record carrier (1) and an apparatus for recording a digital information signal in a track on said record carrier. The apparatus comprises an input terminal (40) for receiving the digital information signal, an encoding unit (42) for encoding the digital information signal so as to obtain a digital channel signal suitable for recording, and a writing unit (44) for writing the digital channel signal in the track on the record carrier. The writing unit (44) comprises at least one write head (2) having a specific gap width (g). The apparatus is adapted to write the digital channel signal in the record carrier, with a bit-length which is smaller than 0.25 mu m and the record carrier (1) has an oblique easy-axis angle between 26 DEG and 35 DEG with regard to the longitudinal direction of the track and in a plane perpendicular to the record carrier.