Fm magnetic recording and sensing utilizing bit periods of different lengths

Claim 2

Apparatus for reading and recovering data previously stored as magnetic information bits on a magnetizable surface, said apparatus comprising transducer means for generating electric information signals during relative movement between said transducer and said surface, each said electric information signal having a period proportional to its encoded data value in a predetermined numbering system, period detection means for determining the time duration of the period of each electric information signal generated by sad transducer means, storage means for storing a constant proportional to the time duration of the period of at least a portion of a next preceding prior information signal read by said transducer, and comparator means responsive to said storage means and the value of the period for each information signal for comparing the time duration of each successive electric information signal as it is read with the stored prior period constant to detect and denominate the content of each said information signal.

Claim 3

The apparatus defined in claim 1 wherein said data is encoded in binary form and wherein the ratio of the period of a binary ''''1'''' signal to the period for a binary ''''0'''' signal is in the order of 1.34.

Claim 4

The apparatus defined in claim 1 wherein said period detection means and said storage means comprise a plurality of cascaded bistable elements and wherein said comparator means comprises digital logical circuitry.

Claim 5

The apparatus defined in claim 1 wherein said storage means comprises a plurality of sequentially energizable capacitor elements and wherein said comparator means comprises logical gating means for comparing the relative analog charge level on capacitors functionally related to the present information signal and the previous period information signal, respectively.

Claim 6

The apparatus defined in claim 1 wherein said data is encoded in an n + 1 order code and said storage means stores n constants proportional to the time duration of the period of at least a portion of a next preceding prior information signal generated by said transducer.

Claim 7

The apparatus defined in claim 1 wherein said stored prior period constant is proportional to the time duration of the periods of two next preceding prior information signals ready by said transducer, said prior period constant being proportional in the order of 1, 7/8 and 7/6 when said data is encoded in binary form and said encoded data value of said two next preceding prior information signals is 01 or 10, 11 and 00 respectively.

Claim 8

Apparatus for reading and recovering data previously stored as magnetic bits on a magnetic surface, said apparatus comprising transducer means for generating electric information signals during relative movement between said transducer means and said surface, each of said electric information signals having a period proportional to its eNcoded data value in accordance with a predetermined numbering system, computing means responsive to said electric information signals for computing a prior period constant proportional to the duration of the periods of a predetermined number of next preceding electric information signals, and comparator means responsive to said computing means and each of said electric information signals for comparing said prior period constant with the period of each electric information signal as it is read to detect and denominate the data value of each of said electric information signals.

Claim 9

Apparatus for reading and recovering data previously stored as magnetic bits on a magnetic surface, said apparatus comprising transducer means for generating electric information signals during relative movement between said transducer means and said surface, each of said electric information signals having a period proportional to its eNcoded data value in accordance with a predetermined numbering system, computing means responsive to said electric information signals for computing a prior period constant proportional to the duration of the periods of a predetermined number of next preceding electric information signals, and comparator means responsive to said computing means and each of said electric information signals for comparing said prior period constant with the period of each electric information signal as it is read to detect and denominate the data value of each of said electric information signals.

Claim 10

The apparatus defined in claim 7 wherein said computing means comprises a first means responsive to said electric information signals for counting and storing a count proportional to the time duration of said predetermined number of next preceding electric information signals, second means responsive to said first means for averaging said count of said first means and storing said averaged count, and altering means responsive to said averaged count and the encoded data value of said predetermined number of next preceding electric information signals for altering said averaged count to determine said prior period constant, said altering means including adding and subtracting means for varying the count of said averaged count.

Claim 11

The apparatus defined in claim 8 wherein said electric information signals are encoded in binary form and said averaged count is altered by adding to and subtracting counts from said averaged count to effectively multiply said averaged count by 1, 7/8, and 7/6 when said predetermined number of next preceding electric information signals is two and said next preceding information signals have the binary value of 01 or 10, 11 and 00 respectively.

Claim 12

The apparatus defined in claim 8 wherein said first means comprises a plurality of cascaded bistable elements; said second means comprises logical gating circuitry for averaging by shifting said count of said first means a predetermined number of positions and a plurality of cascaded bistable elements for storing said averaged count, and said altering means comprises a variable count counter for altering the averaged count stored in said second means.

Claim 13

The apparatus defined in claim 7 wherein said computing means comprises a plurality of sequentially energizable capacitor elements and said prior period constant is an analog charge level being a function of the encoded data value of said predetermined number of preceding bits, said energizable capacitor elements being chargeable during the periods of said predetermined number of next preceding electric information signals to said analog charge level.

Claim 14

Apparatus for reading and recovering data previously stored as magnetic information bits on a magnetizable surface, said apparatus comprising: transducer means for generating electric information signals during relative movement between said transducer means and said magnetizable surface, each of said electric information signals having a period proportional to its encoded data value in a predetermined numbering system period detection means responsive to said electric information signals for detecting the time duration of a period between selected zero-crossover points of each of said electric information signals generated by said transducer means, computing means operatively associated with said period detection means and operable to compute a constant proportional to a selected number of said detected periods of at least one next preceding electric information signal, and comparator means responsive to said computer means and said period detection means for comparing the time duration of the detected period of each electric information signal as it is read with the constant to detect and denominate the content of each electric information signal.

Claim 15

Apparatus for reading and recovering data previously stored as magnetic information bits on a magnetizable surface, said apparatus comprising: transducer means for generating electric information signals during relative movement between said transducer means and said magnetizable surface, each of said electric information signals having a period proportional to its encoded data value in a predetermined numbering system period detection means responsive to said electric information signals for detecting the time duration of a period between selected zero-crossover points of each of said electric information signals generated by said transducer means, computing means operatively associated with said period detection means and operable to compute a constant proportional to a selected number of said detected periods of at least one next preceding electric information signal, and comparator means responsive to said computer means and said period detection means for comparing the time duration of the detected period of each electric information signal as it is read with the constant to detect and denominate the content of each electric information signal.

Claim 16

The apparatus defined in claim 12 wherein said eNcoded data value is in binary form, said detected period of an electric information signal having the binary encoded value of 1 has a duration of 300 microseconds, said detected period of an electric information signal having the binary encoded value of 0 has a duration of 224 microseconds and said preceding period constant has a duration of 262 microseconds.

Claim 17

Apparatus for reading and recovering encoded data previously stored on a magnetizable surface as variable period information bits, said apparatus comprising: transducer means for generating electric information signals in response to relative movement between said transducer means and said surface, each of said electric information signals having a period proportional to its encoded data value in a predetermined numbering system, means for generating a pattern of clock pulses, control means responsive to said electric information signals generated by said transducer means and said clock pulses for generating control signals, first bistable counter means responsive to said control signals for counting a first count proportional to the periods of a predetermined number of next preceding electric information signals, logical gating means responsive to said control signals for performing an averaging operation of the periods of said predetermined number of next preceding electric information signals and generating a second count representative thereof, second bistable counter means associated with said logical gating means for storing said second count, said second count being transferred by said logical gating means in response to said control signals, variable counter means associated with said second bistable counter means and responsive to said control signals for varying said second count stored in said second bistable counter means, said variable counter means including means for effectively multiplying said second count stored in said second bistable counter means by a constant proportional to the encoded data values of said predetermined number of next preceding electric information signals, a resulting product of said effective multiplication being a threshold value proportional to said periods of said predetermined number of next preceding electric information signals, and comparator means associated with said variable counter means and responsive to said control signals for comparing said threshold value with the period of an electric information signal as it is being read, said comparator means including denominating means responsive to said control signals for designating a first value when said threshold value is greater than the period of said read electric information signal and a second value when said threshold value is less than the period of said read electric information signal.

Claim 18

Apparatus for reading and recovering encoded data previously stored on a magnetizable surface as variable period information bits, said apparatus comprising: transducer means for generating electric information signals in response to relative movement between said transducer means and said surface, each of said electric information signals having a period proportional to its encoded data value in a predetermined numbering system, means for generating a pattern of clock pulses, control means responsive to said electric information signals generated by said transducer means and said clock pulses for generating control signals, first bistable counter means responsive to said control signals for counting a first count proportional to the periods of a predetermined number of next preceding electric information signals, logical gating means responsive to said control signals for performing an averaging operation of the periods of said predetermined number of next preceding electric information signals and generating a second count representative thereof, second bistable counter means associated with said logical gating means for storing said second count, said second count being transferred by said logical gating means in response to said control signals, variable counter means associated with said second bistable counter means and responsive to said control signals for varying said second count stored in said second bistable counter means, said variable counter means including means for effectively multiplying said second count stored in said second bistable counter means by a constant proportional to the encoded data values of said predetermined number of next preceding electric information signals, a resulting product of said effective multiplication being a threshold value proportional to said periods of said predetermined number of next preceding electric information signals, and comparator means associated with said variable counter means and responsive to said control signals for comparing said threshold value with the period of an electric information signal as it is being read, said comparator means including denominating means responsive to said control signals for designating a first value when said threshold value is greater than the period of said read electric information signal and a second value when said threshold value is less than the period of said read electric information signal.

Claim 19

The apparatus defined in claim 14 wherein said comparator means includes means responsive to said control signals for counting down said threshold value stored in said second bistable counter means for the period of said read electric information signal and means responsive to said control signals for interrogating said second bistable counter means after the period of said read electric information signal to determine the count remaining in said second bistable counter means, said remaining count being determinative of said first and said second values.

Claim 20

The apparatus defined in claim 15 wherein said second bistable counter means stores the complement of said threshold value and said comparator means counts up the complement of said threshold value.

Claim 21

The apparatus defined in claim 14 wherein said data is encoded in binary form, said predetermined number of next preceding electric information signals is two and said variable counter means effectively multiplies said second count by 1, 7/8 and 7/6 when the encoded data value of said next two preceding electric information signals is a binary ''''01'''' or ''''10,'''' ''''11'''' and ''''00'''' respectively.

Claim 22

The apparatus defined in claim 17 wherein said electric information signals having a binary value of 1 have a period of 300 microseconds, said electric information signals having a binary value of 0 have a period of 224 microseconds, and said threshold value has a period of 262 microseconds.

Claim 23

The apparatus defined in claim 14 wherein variable counter means has a modulus other than the modulus of said second bistable counting means and said timing and control means comprises a multiple state control means for controlling sad first and second bistable counter means, said logical gating means, said variable counter means and said comparator means, said multiple states of said state control means being responsive to said electric information signals.

Claim 24

Apparatus for sequentially reading and recovering encoded data previously stored on a magnetizable surface as variable period duration information bits, said apparatus comprising transducer means for generating electric signals during relative movement between said transducer and said magnetizable surface, each said electric signal having a period proportional to its value in a predetermined numbering system, oscillator means for generating a pattern of clock pulses, timing means responsive to an electric signal from said transducer means and pulses from said oscillator means for generating a pattern of logical timing signals, first bistable counter means responsive to said timing means and said oscillator means for generating a count for each electric information signal generated by said transducer, said count being proportional to the respective period of each said electric signal generated by said transducer, second bistable counter means responsive to the count stored in said first counter means for periodically registering a prior period constant count proportional to the average of the duration of the periods of at least two of the next preceding electric information signals generated by said transducer, and comparator means for determining the value of said sequentially read electric signals by comparing the period of each such electric signal with the previously stored prior period constant.

Claim 25

Apparatus for sequentially reading and recovering encoded data previously stored on a magnetizable surface as variable period duration information bits, said apparatus comprising transducer means for generating electric signals during relative movement between said transducer and said magnetizable surface, each said electric signal having a period proportional to its value in a predetermined numbering system, oscillator means for generating a pattern of clock pulses, timing means responsive to an electric signal from said transducer means and pulses from said oscillator means for generating a pattern of logical timing signals, first bistable counter means responsive to said timing means and said oscillator means for generating a count for each electric information signal generated by said transducer, said count being proportional to the respective period of each said electric signal generated by said transducer, second bistable counter means responsive to the count stored in said first counter means for periodically registering a prior period constant count proportional to the average of the duration of the periods of at least two of the next preceding electric information signals generated by said transducer, and comparator means for determining the value of said sequentially read electric signals by comparing the period of each such electric signal with the previously stored prior period constant.

Claim 28

The method of claim 21 additionally including the step of temporarily storing data which is expressed in a first numbering system and which is to be encoded and recorded and wherein the step of selectively generating an individual current waveform for each respective value of data includes the step of selectively generating a write current waveform having a predetermined period determined in accordance with the respective value of the data to be encoded.

Claim 29

The method of claim 21 wherein the data to be encoded is expressed in binary form and wherein the step of selectively generating variable period current waveforms comprises the step of generating a current waveform of a first period for the binary ''''0'''' value and a second period for a binary ''''1'''' value, respectively and wherein the ratio of the current waveform period of the binary ''''1'''' waveform to the binary ''''0'''' waveform is within the range of 1.2 to 1.8.

Claim 30

The method of claim 23 wherein the step of generating a current waveform of a first period for a binary ''''0'''' value and a second period for a binary ''''1'''' value coMprises the step of generating first half periods in said first and second periods having a duration of 112 microseconds and second half periods having a duration of 112 microseconds and microseconds in said first and second periods respectively.

Claim 33

The method of claim 25 additionally including the step of modifying the value of said stored constant after each successive comparison step to reestablish the constant at a predetermined threshold detection value.

Claim 34

The method of claim 26 additionally including the steps of initially reading predetermined data values into said apparatus via said transducer at the beginning of each read operation, and establishing an initially known threshold value in response to said reading in of said predetermined data.

Claim 37

The method of encoding data according to claim 21 wherein said step of selectively generating single-cycle variable period waveforms is characterized by maintaining a uniform period for one of the two half cycles of each such waveform while varying the period of the other half cycle of each such waveform in accordance with said predetermined data value of said predetermined numbering system.

Claim 38

The method of encoding data according to claim 21 wherein said step of selectively generating single-cycle variable period waveforms is characterized by generating a uniform first half cycle and a variable second half cycle in accordance with said predetermined data value of sad predetermined numbering system.

Claim 39

The method according to claim 25 wherein the step of comparing the period is characterized by recognizing a first binary value for a period less than the threshold value and recognizing a second binary value for a period greater than the threshold value.

Claim 40

The method according to claim 28 wherein said storeD constant is determined by the steps of: measuring the periods of a predetermined number of immediately preceding waveforms; storing a value corresponding to the periods of said immediately preceding waveforms; and modifying said stored value in accordance with a predetermined mathematical scheme to compute said stored constant.

Claim 41

The method according to claim 32 comprising the additional step of computing a new stored constant for each waveform.

Claim 42

The method according to claim 28 wherein the step of comparing the period of each waveform is characterized by assigning a first data value to all waveforms having a period less than the stored constant and by assigning a second data value to all waveforms having a period greater than the stored constant.