SU1674227A1 - Device for digital information reproducing from magnetic tape - Google Patents

Abstract

The invention relates to magnetic information storage devices and can be used in digital recording and playback devices for input and subsequent processing in a computer. The purpose of the invention is to reduce the error in reproducing an asynchronous digit information. The device contains a differential amplifier 1, connected via comparators 2, 3, circuits 5, 6, asynchronous information bindings, an element OR 8, a divider 9 into two, a trigger 10 with an output bus. 3 il.

Description

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The invention relates to magnetic information storage devices and can be used in digital recording and reproducing devices for its input and subsequent processing in a computer.

The aim of the invention is to reduce the error in reproducing asynchronous digital information.

FIG. 1 shows a block diagram of the device; in fig. 2 - time diagram of the device; in fig. Pros, b - scheme and temporal diagram of the asynchronous information binding scheme.

The device (Fig. 1) contains a differential amplifier 1, the direct and inverse outputs of which are connected to comparators 2 and 3, the second inputs of which are connected to the source 4 of the reference voltages, and the outputs of the comparator are connected to the first inputs of the circuits 5.6 Asynchronous information, the second inputs of which are connected to the generator 7 pulses, the outputs of the binding circuit are connected to the inputs of the element OR 8, the output of which is connected via divider 9 to two to the clock bypass of the trigger 10, the inverse output of the coupling circuit 6 is connected to the potential input of the trigger 1 0, the output of which is the output of the device.

The device works as follows.

The waveform readable from a magnetic tape is shown in (Fig. 2a), where changes in the shape of the curve due to noise factors in the tape-recording path of the tape recorder are shown at section C and A, and changes in the signal form from the parasitic amplitude at section C and D modulation.

The signal read from the magnetic tape is fed to the input of the differential amplifier 1, from the outputs of which the direct and inverse signals go to the first inputs of comparators 2 and 3, and the second inputs of the comparators receive levels 1 and 2 (Fig. 2a) specified from source 4 As a result of the operation of the comparators (Fig. 26 and c), when the levels of the reference signals increase and under the condition that there are currently pulse inputs from the generator 7 (fig. 2 g) at the inputs of the circuits 5,6, one of the circuits (Fig. 2d, e). The signals from the direct outputs of the circuits through the element OR 8 arrive at the input of the divider 9 into two (Fig. 2g), from the output of which (Fig. 2h) the clock input of the trigger 10 receives the clock pulses. If there is a single level coming from the inverse output of the attachment circuit b, a trigger 10 will be triggered, the output of which is the recovered code of the recorded information (Fig. 3g).

Due to significant distortions of the signal at the input, the reproducing unit, both in shape and amplitude, is associated with the noise characteristics of the recording / reproducing path of the tape recorder and with the parasitic amplitude modulated, the signal form at the input of the differential amplifier is the curve shown in FIG. . 2. It shows that in order to read the signal correctly, it is necessary to set the optimum response levels of the drivers.

The use of comparators 2.3 in the device makes it possible to establish their response levels (see Fig. 2) with high accuracy and stability, since the reference inputs are supplied to the second inputs of the comparators

voltages from source 4, allowing adjustment of the specified levels.

The asynchronous information binding scheme (see FIG. 3a) is a combination of IK-flip-flops and an NAND element.

Scheme binding asynchronous information (see Fig. 3) works as follows.

The input I of the element 2I-NOT is given a signal from the comparator, and the input C-clock

pulses from the generator. From the timing diagram it can be seen that the signal at the output Q of the asynchronous information looping scheme on Wits only after the coincidence of the signal at input I and the clock pulse at input C.

If the false triggering according to clock between pulses, the signal at the output Q of the asynchronous information looping scheme does not work. The pulse duration at the output Q of the asynchronous information binding circuit is determined by the frequency of the clock pulses at input C and is chosen so that the frequency of the clock pulses is not less than twice the frequency of the appearance of the information signal at

input I. Thus, the joint operation of comparators and asynchronous information binding schemes ensures high reliability of the entire device, since the inputs of the divider 9 are two and the trigger 10

(see Fig. 1) impulses of a certain duration and amplitude are strictly synchronized with each other, which are not affected by the false positives of the comparators (false impulses, fig.

26) and interference in the intervals between the clock pulses (Fig. 2d), which allows one to eliminate signal distortions arising during the operation of the information reproduction device.

The asynchronous information binding scheme can be reactivated only after the end of the clock pulse duration, so if the clock period is longer than the comparators bounce, the asynchronous information loop circuit will trigger at the beginning of the bounce, not responding to other bounce pulses.

The setting of the level of operation of the comparators will be considered in the section of the characteristic curve (Fig. 2a, section C). The value of the reference voltage Ui is limited from above by the distortions of the information signal level, therefore, the level Ui is chosen so as not to be affected by a change in the signal amplitude at the maximum of its value (to the left of section C). The trigger level of the comparator Ui from below is limited by the level below which a false trigger can be said due to a random transition through the middle line of the useful signal (section D). Similarly, the level of the reference voltage U2 is selected. Thus, the trigger levels of the comparators Ui and Uz should be set between 0.4 and 0.8 of the maximum possible value of the signal at the input of the comparator.

Claims (1)

Invention Formula A device for reproducing digital information from a magnetic tape, containing a differential amplifier, OR connected in series, a divider into two and a trigger, the direct output of which is an output of the device, about which. that, in order to reduce the reproduction error of asynchronous information, a reference voltage source, an impulse generator, two comparators and two attachment circuits were entered into it, and the direct and inverse outputs of the differential amplifier are connected to the first inputs of the first and second comparators, respectively , the second inputs of the comparators are connected to the outputs of the source of reference voltages, the outputs of the first and The second comparators are connected to one input of the first and second binding circuits, respectively; the direct outputs of the coupling circuit are connected to the inputs of the OR element; the inverse output of the second coupling circuit connected to the potential trigger input, and the clock inputs of the binding circuit are connected to the output of the pulse generator. / 1PGP ini in tpppppppppppppppppppppppppppppppppppppppppppppp ABOUT 1P1 pi needles 1P1 FIG. 2 ppppppppppp S) FIG. five