Patent US3826975A successfully refreshed from Google Patents.
US3826975A
Expired / Lapsed
US
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Universal dropout tester for magnetic storage media
Assignee: United States Department of Commerce
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Filing: 1973-08-29
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Granted: 1974-07-30
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Expires: 1993-08-29
Abstract
Abstract A method and apparatus are disclosed for testing the dropout response of a magnetic recording medium by detecting and counting dropouts present on the recorded magnetic recording medium. A pulse (which may be on any one of a number of fundamental frequencies) is recorded on the magnetic storage medium. When the level of the reproduced tone is below a given amplitude level, a timing apparatus consisting of a linear ramp generator and comparator is activated. The comparator produces an output pulse each time the level of the signal produced by the linear ramp generator falls below a given amplitude level. The production of each output pulse reflects that the dropout has persisted for a reference time unit. The number of pulses produced during any given dropout is a measure of the duration of the entire dropout in reference time units. The total number of pulses produced by the comparator is stored in a counter, the count reflecting the dropout performance of the magnetic storage media.
Inventors
- 👤 S Geller
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 18:54
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/12; G01R33/1207
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
223 words
In an apparatus for detecting dropouts present on a recorded magnetic medium, the combination comprising: first means for reproducing the signal recorded on said magnetic tape; second means coupled to said first means for producing a control signal of a first amplitude level when said reproduced signal is above a predetermined amplitude level and for producing a control signal of a second amplitude level when said reproduced signal is below said predetermined amplitude level; signal generating means coupled to said second means, said signal generating means producing a signal having a cycle time equal to a reference time unit, the signal from said signal generating means not reaching a predetermined magnitude if the control signal of said second amplitude level produced by said second means persists for less than the reference time unit, the signal from said signal generating means reaching the predetermined magnitude once during every reference time unit that the control signal of said second amplitude level produced by said second means persists; and third means coupled to said signal generating means for producing an output signal of a first amplitude level each time said signal from said signal generating means is above the predetermined magnitude and for producing an output signal of a second amplitude level each time said signal from said signal generating means is below said predetermined magnitude.
Claim 2
Dependent Claim
223 words
In an apparatus for detecting dropouts present on a recorded magnetic medium, the combination comprising: first means for reproducing the signal recorded on said magnetic tape; second means coupled to said first means for producing a control signal of a first amplitude level when said reproduced signal is above a predetermined amplitude level and for producing a control signal of a second amplitude level when said reproduced signal is below said predetermined amplitude level; signal generating means coupled to said second means, said signal generating means producing a signal having a cycle time equal to a reference time unit, the signal from said signal generating means not reaching a predetermined magnitude if the control signal of said second amplitude level produced by said second means persists for less than the reference time unit, the signal from said signal generating means reaching the predetermined magnitude once during every reference time unit that the control signal of said second amplitude level produced by said second means persists; and third means coupled to said signal generating means for producing an output signal of a first amplitude level each time said signal from said signal generating means is above the predetermined magnitude and for producing an output signal of a second amplitude level each time said signal from said signal generating means is below said predetermined magnitude.
Claim 3
Dependent Claim
41 words
In an apparatus for detecting dropouts as recited in claim 1 further comprising a fourth means coupled to said third means for counting the number of times the output signal produced by said fourth means is at said first amplitude level.
Claim 4
Dependent Claim
168 words
In an apparatus for detecting dropouts as recited in claim 2 further comprising: fifth means coupled to said first means and to said signal generating means, said fifth means inverting and amplifying the signal reproduced by said first means to produce a pulse at each zero crossover point of the reproduced signal; said fifth means ''''triggering'''' the cycle time of the signals produced by the signal generating means to the frequency of the pulses when the amplitude of said reproduced signal is greater than a predetermined percentage of the amplitude of the nominal level of the reproduced signal without dropouts, whereby said signal generating means operates in a ''''controlled generator'''' mode; and said fifth means not ''''triggering'''' the cycle time of the signals generated by said signal generating means to the frequency of the pulses when the amplitude of said reproduced signal is less than the predetermined percentage of the nominal level of the recorded signal without dropouts whereby said signal generating means operates in a ''''free-running'''' mode.
Claim 5
Dependent Claim
21 words
In an apparatus for detecting dropouts as recited in claim 3 wherein said pulse generating means comprises a linear ramp generator.
Claim 6
Dependent Claim
59 words
In an apparatus for detecting dropouts as recited in claim 4 wherein said first means comprises: a readout magnetic head; amplification means coupled to said readout magnetic head for amplifying the signal reproduced from said tape; and rectifying and amplifying means coupled to said amplification means for producing rectified, amplified pulses from said signal produced by said amplification means.
Claim 7
Dependent Claim
25 words
In an apparatus for detecting dropouts as recited in claim 5 further comprising a means for recording a pulse signal on said magnetic recording medium.
Claim 8
Dependent Claim
88 words
In an apparatus for detecting dropouts as recited in claim 6 further comprising: a first ''''And'''' gate having first and second inputs and one output; said first input being coupled to an output of said third means; said second input being coupled to an output of said fifth means; and a first switch having an input and an output, the input of said first switch being coupled to the output of said first ''''And'''' gate and the output of said first switch being coupled to said fourth means.
Claim 9
Dependent Claim
127 words
In an apparatus for detecting dropouts as recited in claim 7 further comprising: a flip-flop having a first toggle input and a second input and an output, said first toggle input being coupled to an output of said second means, said second input being coupled to the output of said first ''''And'''' gate; and a second ''''And'''' gate having first and second inputs and one output, said first input being coupled to said output of said flip-flop, said second input being coupled to said output of said first ''''And'''' gate, a second switch having an input and an output, the input of said second switch being coupled to the output of said second ''''And'''' gate, the output of the second switch being coupled to said fourth means.
Claim 10
Dependent Claim
113 words
In an apparatus for detecting dropouts as recited in claim 6 wherein said second means comprises: a comparator having an input and an output, said comparator producing an output signal of a first level when said reproduced signal is above a given level and producing an output signal of a second level when said reproduced signal is below a given level, the input of said comparator being coupled to said first means; and a retriggerable one-shot multivibrator coupled to the output of said comparator, said retriggerable one-shot multivibrator having an astable state of approximately the same duration as the time between successive pulses of the rectified amplifier signal produced by said first means.
Claim 11
Dependent Claim
200 words
In an apparatus for detecting dropouts as recited in claim 9 further comprising: an alternating current signal generator of variable frequency; a third switch having two inputs and an output, the first input of said third switch being coupled to said readout magnetic head and the second input being coupled to said alternating current generator; a potentiometer having an input and an output, said input being coupled to the output of said third switch; a fourth switch having an input and two outputs, the input of said fourth switch being coupled to the output of said potentiometer; an amplifier having an input and an output, the first output of said fourth switch being coupled to said input of said amplifier, the second output of said fourth switch being coupLed to said rectifying and amplifying means of said first means; and a fifth switch having two inputs and an output, a first input of said fifth switch being coupled to the output of said amplifier, the second input of said switch being coupled to said rectifying and amplifying means of said first means, the output of said fifth switch means coupled to the input of said comparator of said second means.
Claim 12
Dependent Claim
71 words
In an apparatus for detecting dropouts as recited in claim 10 further comprising an automatic gain control circuit having an input and an output, the input of said automatic gain control circuit being coupled to the first output of said fourth switch, the output of said automatic gain control circuit being coupled to a second input of said amplifier whose output is coupled to the first input of said fifth switch.
Claim 13
Dependent Claim
89 words
In an apparatus for detecting dropouts as recited in claim 10 further comprising: a sixth switch having an input and an output, the input of said sixth switch being coupled to said fifth means, the output of said switch being coupled to said signal generating means; and a seventh switch having an input and an output, the input of said seventh switch being coupled to an output of said signal generating means, the output of said seventh switch being coupled to the first input of said first ''''And'''' gate.
Claim 14
Independent Claim
164 words
A method for detecting and counting dropouts comprising the steps of: recording a signal on a magnetic storage medium; reproducing the recorded signal; generating a control signal at a first amplitude level if the amplitude of the reproduced signal is of a greater magnitude than a predetermined amplitude; generating a control signal at a second amplitude level if the amplitude of the reproduced signal is less than the predetermined amplitude; timing the duration of the control signal at the second amplitude level to detect any duration longer than a reference time unit; generating a pulse when the duration of the control signal at the second amplitude level is equal to the reference time unit, but not producing a pulse when the duration of the control signal of the second amplitude level is less than the reference time unit; generating an additional pulse for each successive reference time unit that the control signal persists at the second amplitude level; and counting the number of pulses.
Claim 15
Independent Claim
164 words
A method for detecting and counting dropouts comprising the steps of: recording a signal on a magnetic storage medium; reproducing the recorded signal; generating a control signal at a first amplitude level if the amplitude of the reproduced signal is of a greater magnitude than a predetermined amplitude; generating a control signal at a second amplitude level if the amplitude of the reproduced signal is less than the predetermined amplitude; timing the duration of the control signal at the second amplitude level to detect any duration longer than a reference time unit; generating a pulse when the duration of the control signal at the second amplitude level is equal to the reference time unit, but not producing a pulse when the duration of the control signal of the second amplitude level is less than the reference time unit; generating an additional pulse for each successive reference time unit that the control signal persists at the second amplitude level; and counting the number of pulses.
Claim 16
Dependent Claim
125 words
A method for detecting and counting dropouts as recited in claim 13 comprising the additional steps of: rectifying the reproduced signal; inverting the rectified signal; amplifying the inverted signal to form a series of spikes at the zero crossover points of the inverted signal; ''''triggering'''' the repetition frequency of the series of one or more pulses with the series of spikes when the amplitude of reproduced signals is greater than a predetermined percentage of the nominal level of the reproduced signal without dropouts; and generating pulses at the frequency of the series of spikes when the amplitude of the spikes fall below a predetermined percentage of the nominal level of the reproduced signal without dropouts, said pulses not being ''''triggered'''' by the series of spikes.
Claim 17
Dependent Claim
69 words
A method for detecting and counting dropouts as recited in claim 14 wherein the step of timing the duration of the control signal at the second amplitude level comprises the additional steps of: activating a linear ramp generator to produce a linear ramp signal while the control signal is at the second level; and comparing the amplitude of the linear ramp signal with the amplitude of a reference signal.
Claim 18
Dependent Claim
132 words
A method for detecting and counting dropouts as recited in claim 13 wherein the steps of generating the control signal of the first and second amplitude levels comprise the steps of: producing a pulse each time the reproduced signal is above a predetermined magnitude; and ''''triggering'''' the retriggerable monostable circuit with said pulses into An astable state with each pulse, the duration of each astable state being equal to the time between successive pulses, the control signal of the first amplitude level being produced by the retriggerable monostable circuit in its astable state when the reproduced signal''s magnitude exceeds the predetermined level, the control signal of the second amplitude level being produced by the retriggerable monostable circuit in its stable state when the reproduced signal''s magnitude is less than the predetermined level.
References Cited (Backward Citations)
US3525930A
Cited
US3755731A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-07-29 | 1978-01-28 | 1978-07-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-07-29 | 1982-01-28 | 1982-07-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-07-29 | 1986-01-28 | 1986-07-30 | $7700.00 | Window Closed / Lapsed |