SU1195380A1 - Device for reproducing digital information from magnetic record medium - Google Patents

Description

The invention relates to magnetic recording, in particular, to devices for reproducing digital information from magnetic recording media.

- The purpose of the invention is to reduce the error in a wide frequency range of the reproduced signal.

The drawing shows a functional diagram of a device for reproducing digital information from a magnetic recording medium.

A device for reproducing digital information from a magnetic recording medium contains a playback amplifier 1 connected by an input to an input bus 2 and an output through shapers of 3 pulses to the inputs of the first element OR 4 connected by an output to the first input of the first element AND 5 connected by an output to the first output bus 6, and through the delay element 7 to the installation input of the first pulse counter 8, connected by outputs to the inputs of the decoder 9, connected by the first output to the input of the first trigger 10, pulse generator 11, connected by the output to the input of the second pulse counter 12, as well as the second element I 13 and the second output bus 14. In addition, the device for reproducing digital information from the magnetic recording media contains the second 15 and third 16 triggers, the register 17, the third counter 18 pulses and the second element OR 19 ,. moreover, the register 17 is connected by information inputs to the outputs of the second counter 12 pulses, the synchronizing input - to the output of the first element OR 4, the blocking input - to the output of the second trigger 15 and the outputs - to the installation2

Vocational inputs of the third counter 18 pulses connected by a counting input to the output of the generator 11 pulses, output to the counting input of the first counter of 8 pulses and a setting input to the output of the second element OR 19 connected by the first input to the interconnected output of the element? delay, the installation input of the second pulse counter and the first installation input of the second trigger 15, the second input with the output of the third pulse counter 18, the second element And 13 connected by the first input to the output of the first element OR 4, the second input to the direct output of the first trigger 19 , output - to the first input of the third trigger 16;

²⁰ output to the second output bus 14, the second input to the output of the first element And 5, connected by a second input to the inverse output of the first trigger 10, 25 installation input connected to the second reset input connected to each other. trigger 15 and the second output of the decoder 9, the third output of which is connected to the second installation 30 output of the second trigger 15.

In addition, the device contains the third element 20 and fourth 21 and fifth 22 triggers, with the fourth trigger 21 being connected to the third output of the decoder 9 by the first installation input to the third output of the decoder 9, the information input to the fourth output of the decoder 9, the synchronizing input to the output of the first element OR 4,

40 second installation input - to

the output of the third element And 20, direct output - to the control bus

^{5 1} '23 and inverse output - to the first. the input of the fifth trigger 23, the second input of which is connected to the second output of the decoder 9 and the output to the first input of the third element I 20, the second input connected to the installation input of the second counter 12 pulses.

The device works as follows. '

Pulse signals carrying in-. digital code information recorded? dual-frequency (two-interval) method, is fed to the input bus 2, which is the input of the playback amplifier 1.

In the event that there are no distortions in the paths of the magnetograph, at the output of the playback amplifier 1 the recorded “1” correspond to two different time intervals, and the “0” corresponds to another time interval.

Due to the imperfection of the Record-Play path, there are always deviations in the durations of the read pulses. Minor deviations are usually caused by the instability of the speed of the magnetic carrier and the influence of the written code combination on the parameters of the read signals. . A significant difference in the durations of time intervals is associated with a transition to a different speed of magnetic carrier or. change the frequency of formation of codes when they are written.

In this case, the time intervals differ by a factor of two or more, since for modern magnetographs the speed of the carrier is regulated in a wide range.

The device automatically measures the time intervals, analyzes the values obtained and, based on the results of the analysis, performs decoding. For this, using a pulse generator 3 and the first element OR 4, a sequence of short pulses is formed, the time intervals between which are converted into code using counter 12 and generator 11. Counter code 12 is rewritten to register 17 with a shift to the lower digit to the left.

At the stage of conversion into a code, the time interval is compared with the previously obtained value of the time interval stored in register 17. This is achieved by the fact that the delayed pulse delayed by the delay element 7

380 ⁴

clears the counter 12 and through the second element OR 19 rewrites the contents of the 'register 17 into the third subtractive counter 18 pulses. With frequency

5 of the generator 11 pulses in the counter 12, the code of the new time interval is formed, and in the counter 18 the code decreases to zero.

At the time of reaching the counter 18

At the exit of the zero code, a short pulse appears at its output, separated from the recording strobe for a certain time. This pulse through the element OR 19 again overwrites the contents of the reg15 of gistra 17 into the counter 18 and the formation of the next time interval is resumed. The first counter 8 pulses summarizes the output pulses of the third counter 18 and forms

20 code in time units. As the code increases in the first counter 8, control pulses appear successively at the outputs of the decoder 9. The signal from the output of the decoder

25 9, delayed from the moment of commencement

conversion for a certain time is used to form the first trigger 10 pulse information extraction, with the second output

₃₀ decoder 9, the signal is formed after another time. This signal resets the first trigger 10 and sets the second trigger 15 to the zero state, blocking the writing of codes to the register 17.

G ⁵ Blocking ensures the recording of codes of those characters whose fronts fall within a specified interval from the beginning of the transformation. Therefore, in the specified interval fall

40

unit symbols entering the device, taking into account distortions and symbols of zero and one unit of another range, and the code of the zero interval

Register 17 is not recorded. If a

45

the decoded pulse signal information edge falls in the region of the pulse information extraction, then corresponds to "1" and the third trigger 16 is set

5 ® through the second element And 13 in one state, otherwise the decoded signal corresponds to "O" and the trigger 16 remains in the zero state. Time Interval Code

55 "1" on the front of the next pulse

The start of the conversion is rewritten to the register. Content change

register 17 leads to a correction

five

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6

units of the time interval and, consequently, to the adaptation of the device.

If the offset range of the pulse front does not fit into the specified limits, the device perceives changes in the signal as a transition to another playback mode.

There are two options for changing the playback mode: the frequency of the pulse signal at the input of the device increases by two or more times or decreases by two or more times. In the first case, the decoded time interval is less than a certain time interval and the new code replaces the one stored in the register. It is possible that the first time for decoding is the time interval “0” rather than “1”. Then the register 17 registers another value of the time interval and several characters are decoded incorrectly before the arrival of the unit. After the conversion of the first time interval "1" it will be entered into the register 17 and the device is ready to work in the new conditions.

For the second variant, it is characteristic that, regardless of the nature of the incoming symbol, the corresponding time interval is greater than the specified one. When decoding such a symbol on all outputs of the decoder 9, the installation signals appear sequentially. The signal from a specific output of the decoder 9, delayed

in relation to the beginning of the conversion for a certain time, sets the second trigger 15 to one state and thereby removes the lock

5 entries in the register. Thus, the generated code of the time interval of the new frequency range is recorded in the register 17. Since the device provides storage in

¹⁰ register of codes of single time intervals, regardless of the sequence of arrival of characters in the register, the necessary code will be recorded. Impulse selection information

The 15th input goes in parallel to the input of the AND 13 element and ensures the formation of the output information in the trigger 16 according to the signals from the output of the first IDN element 4. The reference frequency, separated from the input signal, is removed from the output of the first AND 5 element.

At the boundaries of abrupt changes in the frequency of input signals, a short-term device malfunction is inevitable.

75 properties associated with the initial uncertainty value of the signal. The device reliably records the faulty moments and signals their presence with a sign of an error at the output 23.

The error signal is generated by the fourth trigger 21, the AND element 20 and the fifth trigger 22 by the signals of the decoder 9 and the element 7 / delay.

35 The use of the invention improves the fidelity of reproducing digital information.

Claims (2)

1. DEVICE FOR REPRODUCTION OF DIGITAL INFORMATION FROM MEDIA MAGNET RECORDING; containing a playback amplifier connected by an input to an input bus and output through pulse shapers with inputs of the first element OR connected by an output to the first input of the first element AND connected by an output to the first output bus, and through a delay element to the installation input of the first pulse counter connected by outputs to the inputs of the decoder connected by the first output with the input of the first trigger, a pulse generator connected by the output to the input of the second pulse counter, as well as the second element And the second output bus, characterized in that, in order to reduce the error in shea the frequency range of the reproduced signals, the second and the third are entered into it. triggers, register,. the third pulse counter and the second element OR, and the register is connected by information inputs to the outputs of the second pulse counter, the synchronizing input is connected to the output the first element OR, blocking input - to the output of the second trigger and outputs - to the installation inputs of the third pulse counter, connected by a counting input to the output of the pulse generator, output to the counting input of the first pulse counter and a setting input -. to the output of the second element OR connected by the first input to the interconnected output of the delay element, the installation input of the second pulse counter and the first installation input of the second trigger, the second input to the output of the third pulse counter, the second element AND connected to the first input of the first element OR, the second input - to the direct output of the first trigger, the output - to the first input of the third trigger, connected by the output to the second output bus, the second input - to the output of the first element And, connected a second input with an inverted output of the first flip-flop, connected to the input of the installation connected between a reset input of the second dispenser _{YY £} r _a decoder and the second output, the third output is connected to the second output of the second flip-flop the installation. 2. The device according to p. ^ Characterized in that, in order to reduce the error by detecting a reproduction error on the border of changing the frequency of following the characters two or more times, the third element And the fourth and fifth triggers are entered into it, and even 18 1195380 > 1) 95380 The first trigger is connected by the first setup input to the third output of the decoder, the information input g · to the fourth output of the decoder, the synchronization input - to the output of the first OR element, the second installation input - to the output of the third And element, the direct output to the control bus and the inverse output to the first the input of the fifth trigger, the second input of which is connected to the second output of the decoder and the output to the first input of the third element And, the second input connected to the installation input of the second pulse counter. one