Digital data storage system

Claim 3

The method of claim 1 wherein the number of said amplitude levels is two.

Claim 4

The method of claim 1 wherein the number of said amplitude levels is three.

Claim 5

The method of claim 1 wherein said baseband signal has 3 amplitude levels and wherein the signal data rate is sufficiently high in relation to the system bandwidth that the time response of said system to the data rate of said signal which is to be stored is limited so that only one step of signal level change can be accomplished in each data bit time interval, and two time intervals carrying successive logical data elements of the same value are required to permit a change from one extreme amplitude level to the opposite extreme amplitude level.

Claim 6

The method of claim 1 wherein said baseband signal has 3 amplitude levels and one of said amplitude levels is inscribed as a lateral displacement of the incsribed groove to a maximum displacement position, a second amplitude level is inscribed as a lateral displacement of the inscribed groove to the opposite maximum displacement position, and a third amplitude level is inscribed as a near zero displacement proximate the mean lateral position of the inscribed groove.

Claim 7

The method of claim 1 wherein said baseband signal has 2 amplitude levels and one of said amplitude levels is inscribed as a lateral displacement of the inscribed groove to a maximum displacement position, and the second amplitude level is inscribed as a lateral displacement of the inscribed groove to the opposite maximum displacement position.

Claim 8

The method of claim 1 wherein said digital data is converted to an electrical signal of the NRZ1 form wherein a logical One is represented by a change of the opposite of 2 levels, and a logical Zero is represented by no change of levels.

Claim 9

The method of claim 1 wherein said digital data is converted to an electrical signal of the NRZO form whereby a logical Zero is represented by a change to the opposite of 2 levels, and a logical One is represented by no change of levels.

Claim 10

The method of claim 1 wherein a clock signal is inscribed on the recording medium in conjunction with the data signal.

Claim 11

Apparatus for storing digital data on a data storage medium comprising receiving means for said digital data; a First stage NRZ1 encoding means for converting said data to an NRZ1 electrical signal. a second stage NRZ1 encoding means for further encoding said NRZ1 signal to a double encoded NRZ1 signal. a first stage NRZO encoding means for converting said data to an NRZO electrical signal. a second stage NRZO encoding means for converting said NRZO signal to a double encoded NRZO signal. low pass filter means for compressing each of said double encoded signals into narrower frequency bands. means for imposing said double encoded NRZ1 signal and said double encoded NRZO signal upon the separate and orthogonally related channel circuits of a stereo groove cutting head and means for relatively moving said cutting head in contact with said data storage medium to simultaneously inscribe said NRZ1 and NRZO double encoded signals into said storage medium as a stereo groove therein.

Claim 12

Apparatus for storing digital data on a data storage medium comprising receiving means for said digital data; a First stage NRZ1 encoding means for converting said data to an NRZ1 electrical signal. a second stage NRZ1 encoding means for further encoding said NRZ1 signal to a double encoded NRZ1 signal. a first stage NRZO encoding means for converting said data to an NRZO electrical signal. a second stage NRZO encoding means for converting said NRZO signal to a double encoded NRZO signal. low pass filter means for compressing each of said double encoded signals into narrower frequency bands. means for imposing said double encoded NRZ1 signal and said double encoded NRZO signal upon the separate and orthogonally related channel circuits of a stereo groove cutting head and means for relatively moving said cutting head in contact with said data storage medium to simultaneously inscribe said NRZ1 and NRZO double encoded signals into said storage medium as a stereo groove therein.

Claim 15

The method of claim 11 wherein said NRZ1 and said NRZO electrical signals are inscribed in their respective channels as an undulating groove having displacements along a pair of orthogonally related axes corresponding to variations in their respective data streams.

Claim 16

The method of claim 11 wherein the number of said amplitude levels is 2.

Claim 21

The method of claim 15 wherein the NRZ1 signal after the first stage encoding has the amplitude values of a1, a2, a3, .....am representing a series of m data time intervals, and said second NRZ1 signal after the second stage encoding has the amplitude values b1, b2, b3,.....bm, where bm am + bm 1.

Claim 22

Apparatus for storing digital data on a record medium comprising receiving means for said digital data: a first encoding means for converting said data to an NRZ1 electrical signal: a second encoding means for converting said data to an NRZO electrical signal: means for imposing said NRZ1 signal and said NRZO signal upon the separate and orthogonally related channel circuits of a stereo groove cutting head and means for relatively moving said cutting head in contact with said record medium to simUltaneously inscribe said NRZ1 and NRZO signals into said record medium as a stereo groove therein.

Claim 23

Apparatus for storing digital data on a record medium comprising receiving means for said digital data: a first encoding means for converting said data to an NRZ1 electrical signal: a second encoding means for converting said data to an NRZO electrical signal: means for imposing said NRZ1 signal and said NRZO signal upon the separate and orthogonally related channel circuits of a stereo groove cutting head and means for relatively moving said cutting head in contact with said record medium to simUltaneously inscribe said NRZ1 and NRZO signals into said record medium as a stereo groove therein.

Claim 26

The method of claim 18 wherein said double encoded NRZO data signal is inscribed onto one channel of a stereo groove of a recording medium and said double encoded NRZ1 data signal is simultaneously inscribed onto the other channel of said groove, said data signals being inscribed as clocking complements of each other.

Claim 27

The method of claim 18 wherein the data storage density of said double encoded data streams is increased by directing each of said data signals along separate paths, one path leading to an adding means, the other path leading to a delay circuit delaying said data signal one timing interval T, the delayed signal then being directed to said adding means where said delayed data signal is added to the undelayed data signal to obtain conversion to 3-level data storage.

Claim 28

The method of claim 18 wherein the data density density of said double encoded data stream is increased by passing each of said data streams through a low pass filter to compress said data stream to a reduced bandwidth so that the signal requires two data time intervals to change from one extreme level to the opposite extreme to obtain said 3-level data density.

Claim 31

The method of claim 22 wherein the system bandwidth is essentially 16 kilohertz at cut-off and the digital data is stored at densities permitting data rates of 32 kilobits per second.

Claim 34

The method of claim 24 wherein the said selected signal form is inscribed on one channel of a stereo groove, and the complementary signal form is recorded on the second channel of the stereo groove.

Claim 35

The method of claim 24 wherein said data stream signal and a clock signal are botH inscribed in said record medium and the electrical signal from said transducer passed through a filter to separate said clock signal providing a time basis for said intervals T.

Claim 38

The method of claim 27 wherein the NR20 output electrical signal and the NR21 output electrical signal are read together to syncronize a clock and obtain an accurate clock signal to define a time basis for said intervals T, applying said clock signal to one of said output electrical signals and reading the so clocked output electrical signal at said intervals to recover the original digital data.

Claim 39

The method of claim 27 wherein the recovered signal in each of the stereo channels is subjected to full wave rectification to make data streams in each channel of single polarity pulses and spaces, reading said signals by observing pulses in each time interval that appear above a slicing threshold of approximately 50 percent of the maximum signal level, feeding the two pulse streams through isolating diodes to then combine the two streams to provide a pulse in all timing intervals, using said constant stream of pulses to synchronize an accurate clock, combining a clock signal from said clock with one of said pulse streams and reading the pulse stream at the so clocked intervals to reconstitute and recover the original digital data.

Claim 40

The method of claim 27 wherein error in data storage and recovery is applied to said output electrical signals by converting said output electrical signals to pulse streams by slicing said signals at a selected threshold, comparing simultaneously the two pulse streams at each interval T, observing whether there is at any interval the occurrence of simultaneous pulses or no pulse at all in the two pulse streams, in which cases error is detected and reporting any detected error.

Claim 41

The method of claim 27 wherein said NR21 signal and said NR20 signal are second stage encoded to a double encoded NR21 signal and a double encoded NR20 signal and said double encoded signals are inscribed in the two channels of a stereo-groove and thereafter recovered as output electrical signals, said output signals being read together to syncronize a clock and reading one of said output signals against said syncronized clock to recover the original digital data.

Claim 44

The storage medium of claim 32 wherein said groove has as an inscribed component, a clock signal therefor, said component being a superimposed sinusoidal wave having a period of 1/2 T.

Claim 45

The record disk of claim 32 having a stereo groove inscribed therein wherein an NRZO data stream signal and an NRZ1 data stream signal are inscribed in the respective channels thereof as an undulating groove having displacements along a pair of orthagonally related axes corresponding to variAtions in their respective signals.

Claim 46

The record disk of claim 32 having a storage capacity of at least 1,000 bits per linear inch.