Magnetic data decoder

Claim 2

Apparatus for decoding digital information read from a magnetic medium in the form of a series of voltage pulses representing magnetic flux changes on said magnetic medium and in which the time incidence of the voltage pulses of a succeeding bit time interval are compared with a preselected amount of the measured time duration of the prior bit time interval to determine the data state of the succeeding bit time interval comprising: means for receiving the voltage pulses of said prior bit time interval for determining the beginning and end of said prior bit time interval and for measuring the time duration thereof; and comparison means for receiving the voltage pulses of said succeeding bit time interval and for comparing the time incidence of said time voltage pulses of said succeeding bit time interval with a preselected amount of the time duration of said prior bit time interval to determine the data state of said succeeding bit time interval.

Claim 3

The apparatus of claim 1 wherein said means for measuring the time duration of said prior bit time interval includes a first digital counter.

Claim 4

The apparatus of claim 2 wherein said comparison means includes a second digital counter having a higher counting rate than said first digital counter and coupled to said first digital counter for receiving the count state of said first digital counter at the end of said prior bit time interval.

Claim 5

The apparatus of claim 3 wherein said comparison means includes means for determining the onset of said succeeding bit time interval and for causing thereupon said second digital counter to count down from the count state of said first digital counter at said higher counting rate.

Claim 6

The apparatus of claim 4 wherein said comparison means includes means for comparing the state of said second digital counter with voltage pulses during said succeeding bit time interval.

Claim 7

The apparatus of claim 5 wherein said data state of said succeeding bit time interval is a binary "one" if a voltage pulse occurs before said second digital counter counts down to zero.

Claim 8

The apparatus of claim 3 wherein said second digital counter counts at a rate that is approximately forty percent faster than the counting rate of said first digital counter.

Claim 9

The apparatus of claim 3 wherein said first and second digital counters count at a rate that is considerably higher than the frequency of said series of voltage pulses.

Claim 10

The apparatus of claim 1 wherein said information is encoded on said magnetic medium in a self-clocking format.

Claim 11

The apparatus of claim 1 further comprising means for sensing said magnetic flux changes and for providing said voltage pulses in response thereto.

Claim 12

Apparatus for decoding digital information read from a magnetic medium in the form of a series of voltage pulses representing magnetic flux changes on said magnetic medium comprising: first digital counter means, said first counter means counting at a rate that is considerably higher than the frequency rate of said voltage pulses; means for resetting said first counter means to a count of zero at the beginning of each bit time interval on said magnetic medium, the count reached by said first digital counter prior to being reset being a digital measure of the time duration of the immediately preceding bit time interval; a second digital counter means; means for transferring the count established by said first counter means to said second counter means, said second counter means counting downward to a count of zero at a higher counting rate than the rate at which the first counter means counts upwards; means for detecting when said second digital counter means reaches the count of zero; and means for identifying a voltage pulse from said magnetic medium occurring prior to the time said second counter means reaches a count of zero as a binary "one" from said magnetic medium, and for identifying a voltage pulse from the magnetic medium occurring subsequent to said count of zero as a binary "zero" and as the end of the current bit time interval from said magnetic medium and the beginning of the next bit time interval.

Claim 13

Apparatus for decoding digital information read from a magnetic medium in the form of a series of voltage pulses representing magnetic flux changes on said magnetic medium comprising: first digital counter means, said first counter means counting at a rate that is considerably higher than the frequency rate of said voltage pulses; means for resetting said first counter means to a count of zero at the beginning of each bit time interval on said magnetic medium, the count reached by said first digital counter prior to being reset being a digital measure of the time duration of the immediately preceding bit time interval; a second digital counter means; means for transferring the count established by said first counter means to said second counter means, said second counter means counting downward to a count of zero at a higher counting rate than the rate at which the first counter means counts upwards; means for detecting when said second digital counter means reaches the count of zero; and means for identifying a voltage pulse from said magnetic medium occurring prior to the time said second counter means reaches a count of zero as a binary "one" from said magnetic medium, and for identifying a voltage pulse from the magnetic medium occurring subsequent to said count of zero as a binary "zero" and as the end of the current bit time interval from said magnetic medium and the beginning of the next bit time interval.

Claim 14

The apparatus of claim 11 further providing means for sensing said magnetic flux changes and for providing said voltage pulses in response thereto.

Claim 15

The apparatus of claim 11 wherein said information is encoded on said magnetic medium in a self-clocking format.

Claim 16

The apparatus of claim 11 wherein said second counter means counts at a rate that is approximately 40 percent faster than said first counter means.

Claim 17

Apparatus for decoding digital information read from a magnetic medium in the form of a series of voltage pulses representing magnetic flux changes on said magnetic medium comprising: digital counter means, said counter means counting at a rate substantially higher than the frequency rate of said voltage pulses; means for resetting said counter means to a count of zero at the end of each bit time interval, the count reached by said counter means prior to being reset being a digital measure of the time duration of said bit time interval; means for storing the count reached by said digital counter means prior to being reset; means for determining when said counter means reaches a fixed proportion of the count reached during the preceding bit time interval; and means for identifying a pulse occurring prior to said counter means reaching said fixed proportion as a binary "one" from said medium, and for identifying a pulse occurring subsequent to said count reaching said fixed proportion as a binary "zero" and as the end of the time interval and the beginning of the next bit time interval.

Claim 18

Apparatus for decoding digital information read from a magnetic medium in the form of a series of voltage pulses representing magnetic flux changes on said magnetic medium comprising: digital counter means, said counter means counting at a rate substantially higher than the frequency rate of said voltage pulses; means for resetting said counter means to a count of zero at the end of each bit time interval, the count reached by said counter means prior to being reset being a digital measure of the time duration of said bit time interval; means for storing the count reached by said digital counter means prior to being reset; means for determining when said counter means reaches a fixed proportion of the count reached during the preceding bit time interval; and means for identifying a pulse occurring prior to said counter means reaching said fixed proportion as a binary "one" from said medium, and for identifying a pulse occurring subsequent to said count reaching said fixed proportion as a binary "zero" and as the end of the time interval and the beginning of the next bit time interval.

Claim 19

The apparatus of claim 15 further comprising sensing means for transducing the information recorded on said magnetic medium to said voltage pulses representing said digital information.

Claim 20

The apparatus of claim 15 wherein said information is encoded on said magnetic medium in a self-clocking format.