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Title: Audio signal time-duration converter
Claims: What is claimed is: 1. An audio signal time-duration converter comprising an analog-digital converter means for converting an audio signal into a digital signal, random access memory means connected with said analog-digital converter means for storing the output signal of said analog-digital converter during a predetermined write cycle and for reading out the stored data during a read cycle which is different from said write cycle, a digital-analog converter connected to the output of said memory means for converting the output signal of said memory means to an analog signal, first means for generating write clock pulses and read clock pulses at different rates for controlling said memory means, write address counter means connected to said first means for counting the pulse cycle of said write clock pulses, read address counter means connected to said first means for counting the pulse cycle of said read clock pulses, second means connected to said first means, said write address counter means and said read address counter means, and controlled by said write clock pulses for selecting either one of the output signal from said write counter means and the output signal from said read address counter means to apply the selected output signal to said memory means thereby to designate an address in said memory means, third means connected to said first means for generating select clock pulses associated with said write clock pulses, and fourth means for applying the select clock pulses to said memory means to determine the write mode or read mode of the address of said memory means designated by said second means. 2. An audio signal time-duration converter according to claim 1, in which said second means selects the output signal from said write address counter means at the time of logic 1 of said write clock pulse and the output signal from said read address counter means at the time of logic 0, and said third means converts the address designated by said second means into a write mode at the time of logic 1 of said write clock pulse and into a read mode at the time of logic 0 of said write clock pulse. 3. An audio signal time-duration converter according to claim 1, further comprising means for fixing the width of said write and read clock pulses generated from said first means. 4. An audio signal time-duration converter according to claim 1, in which said first means comprises one master oscillator and a plurality of frequency dividers and switches, said frequency dividers dividing the clock pulse generated by said master oscillator into a multiplicity of pulse trains with different frequencies, one of said pulse trains being determined as a read clock pulse, said switches being connected to said dividers for selecting one of the pulse trains including said read clock pulse as a write clock pulse. 5. An audio signal time-duration converter comprising an analog-digital converter for converting an audio signal into a digital signal, random access memory means connected with said analog-digital converter for storing therein the output signal of said analog-digital converter during a predetermined write cycle and for reading the stored data during a read cycle which is different from said write cycle, a digital-analog converter connected with said memory means for converting the output signal of said memory means into an analog signal, first means for generating write clock pulses and read clock pulses at different rates for controlling said memory means, second means connected with said first means for fixing the interval of logic 1 of said write clock pulses and the interval of logic 1 of said read clock pulses while lengthening the interval of logic 1 of said read clock pulse as compared with that of said write clock pulse, write address counter means connected with said first means for counting said write clock pulses read address counter means connected with said second means for counting said read clock pulses, third means connected with said second means, said write address counter means and said read address counter means, and controlled by said write clock pulses for selecting either one of the output signal from said write counter means and the output signal from said address counter means to apply the selected output signal to said memory means thereby to designate an address in said memory means, fourth means connected to said second means for generating select clock pulses associated with said write clock pulses to determine the write mode or read mode of the address of said means designated by said third means, fifth means connected to said second means for comparing a signal associated with the write clock pulse and a signal associated with the read clock pulse, said fifth means producing a specified pulse which is at the state of logic 1 only when both of said signals associated with said write and read clock pulses are in the state of logic 1, and sixth means connected to said fifth means and said memory means for producing only a read signal associated with the read pulse by controlling the output signal of said memory means in response to the output pulse of said fifth means. 6. An audio signal time-duration converter according to claim 1, in which said analog-digital converter constitutes a delta modulator having a first integrator included in a feedback loop thereof, said digital-analog converter constitutes a second integrator, the integration constant of at least one of said first and second integrators being variable as related to the write and read cycles, and said audio signal time converter further comprises means for equalizing the output levels of said first integrator and said second integrator. 7. An audio signal time-duration converter according to claim 6, in which the integration constant of said second integrator is fixed and the integration constant of said first integrator is variable in proportion to the write cycle. 8. An audio signal time-duration converter according to claim 1, in which said analog-digital converter constitutes a delta modulator to which audio signals of substantially the same level reproduced from a magnetic tape is applied. 9. An audio signal time-duration converter according to claim 2, in which said second means comprises a first AND gate, a second AND gate and a NOT gate, one input of said first AND gate being connected to said first means, the other input of said first AND gate being connected to said write address counter means, the output of said first AND gate being connected to one input of said NOT gate, one input of said second AND gate being connected to said first means, the other input of said second AND gate being connected to said read address counter means, the input of said second AND gate being connected to the other input of said NOT gate, the output of said NOT gate being connected to said memory means, whereby said write clock pulses are applied to said one input of said first AND gate and the reversed pulses of said write clock pulses are applied to said second AND gate. 10. An audio signal time-duration converter according to claim 5, further comprises seventh means connected to said sixth means and said first means for producing, from the output signals of said sixth means, pulses having the same uniform pulse width as the read clock pulses. Other info: Inventors: Tanizoe, Toshio (Hitachi, JA) Kubota, Takashi (Katsuta, JA) Application Number: 509070 Filing Date: 1974-09-25 Publication_date: 1976-04-06 Assignee: Hitachi, Ltd. (JA) Primary Class(es): 704/503 Other Classes: US Patent Ref:
Other Refs: Primary Examiner: Claffy, Kathleen H. Assistant Examiner: Kemeny, E. S. Attorney: Craig & Antonelli |
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