JPS5997283A - Control circuit of magnetic recorder and reproducer - Google Patents

Abstract

PURPOSE:To prevent the malfunction at switching when a single monostable multivibrator is operated by plural trigger sources, by producing a pulse train eliminating one pulse at a point of time of switching. CONSTITUTION:A magnetic tape is driven intermittently by utilizing a control signal representing track position to realize slow motion reproduction. The circuit includes trigger pulse generators 1, 2, monostable multivibrators 4, 37, output detectors 6, 7, flip-flops 20, 35, a pulse generator 36, a capstan motor 39 and its drive circuit 38. A control signal is considered as an output of the pulse generator 1, a switch 8 changes over the standard reproduction and the slow motion reproduction. A signal missing a control pulse only determining the switching timing of a control signal 24 is produced as an output of an OR gate 34. This control signal is applied to a monostable multivibrator as a slow control means.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a switching circuit, and in particular, to operate a multivibrator in a time-sharing manner without malfunction, or to ensure smooth operation when switching between standard playback and slow motion playback. The present invention relates to a switching circuit for a magnetic recording/reproducing device that generates a control pulse train.

[Prior art]

The prior art will be explained below with reference to FIG. In the figure, 1.2 is a trigger pulse generator, 3, 5.18 are changeover switches, 4 is a monostable multivibrator, 6.7 is an output detector of a monostable multivibrator (hereinafter abbreviated as monomulti) 4', 9 is a constant voltage source. Here, switch 8 is 1
When it is knocked down, switch 3.5 is on the 1 side and switch 8 is on the 1 side.
It is assumed that when the switch 3.5 is turned to the 2 side, the switch 3.5 is turned to the 2 side. Furthermore, the phases of the pulses generated by the trigger pulse generator 1.2 are different. The operation of this circuit is shown in Figure 2(a).
This will be explained below with reference to the main waveform diagrams of (e) to (e). In the figure, 10 indicates the switching time of the switch 8, and 11 to 15 indicate voltage waveforms. Further, the voltage is a trigger input waveform of the monomulti 4, 13 is an operating waveform of the monomulti 4, 14 is a waveform input to the detector 7, and 15 is a waveform input to the detector 6.

Before time 10, switch 3.5.8 is on the 2 side, and the output of generator 2 is input as the mono multi 40 trigger, but after time 10, the output of generator 1 is input. . When the switch 8 is switched and the trigger from the generator 1 is input while the monomulti 4 is in operation and triggered before time 10, the operation of the monomulti 4 is stopped as shown in the figure until the next trigger. The state is immutable. The detector 6.7 detects the falling phase of the signal 15.14, and what is required of this circuit is to detect the falling phase of the signal 15.14 obtained after a certain time from the trigger pulse. It is. However, according to this circuit, the operation of the monomulti is stopped by the pulse immediately after time point 10, so that a phase obtained by shifting the trigger by a desired amount of delay cannot be obtained.

As described above, according to the prior art, when trying to operate a single monomulti in multiple modes with triggers of different phases, there is a drawback that the desired delay operation is not performed at the time of mode switching [the present invention] Purpose] The purpose of the present invention is to prevent malfunctions that occur when switching a single monomulti in a time-division manner using multiple trigger sources with different phases, or to prevent malfunctions that occur at the time of switching between monomultis, or at the same time as switching between monomultis, An object of the present invention is to provide a switching circuit for a magnetic recording/reproducing device that generates a trigger signal.

[Summary of the invention]

The main focus of the present invention is to switch in synchronization with the input pulse in the previous mode and to generate a pulse train from which one pulse at the time of switching is removed, in order to ensure that the operation of the monomulti is completely completed before switching. There is a particular thing.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. Third
In the figure, 20 is a flip-flop, 21 is an inverter, 22 is an AND gate, and the other elements are the same as in the previous figure. While the main part waveform diagram of this circuit is shown in Fig. 4,
Explanation is added below. In FIG. 4, 24 to 29 represent voltage waveforms 51, and 32 represents time. Assume that the output of the pulse generator 1 is represented by a signal 24, and the input to the inverter 210 when the switch 8 is turned from the 2 side to the 1 side is represented by a signal 25. Then, the inverter 21 applies the reverse phase signal of the signal 25 to the reset terminal of the solid flop 20, so the Q output before time 31 is low. Time point 5
After 1, when a repulse is input from the pulse generator 1, data input high is sampled at the rising edge of the repulse, and the Q output changes to no. The Q output of signal 26 is shown. The switches 3.5 are each turned to the 2 side when the signal 26 is high, and are turned to the 1 side when the signal 26 is low. Therefore, when the pulse generator 2 outputs the pulse indicated by the signal 28, the signal 27, which was the output of the AND gate 22 before the time 32, becomes the output of the AND gate 22, and after the time 32, the output of the pulse generator 2 becomes the monomulti 4. Input as a trigger.

Then, the trigger input signal is shown as signal 29, and the operation of the monomulti 4 becomes as shown in signal 30.

Here, the trigger input before time 32 is the pulse generator 1
This occurred at the previous point in time by a period of 31, and since it is guaranteed that the mono-multiple operation is photon-like at time 31, a malfunction unlike the conventional one does not occur. In this example, the diagram is drawn assuming that the time constant of the monomulti 4 remains unchanged before and after time 32, but it is also possible to change the time constant after time 32 to be shorter than before.

Next, another embodiment in which the present invention is applied to a magnetic recording/reproducing device will be described below using the block diagram of FIG. 5 and the main waveform diagram of FIG. 6. In Figure 5, 3
3 is an AND gate, 34 is an OR gate, 35 is a flip-flop, 36 is a pulse generator, 37 is a monomulti, 3
9 is a capstan motor, 38 is a capstan motor 3
This is the No. 9 drive circuit. Further, the voltage signal 42 at 40, 41, etc. in FIG. 6 is a time signal.

A magnetic recording and reproducing device that records and reproduces video signals diagonally on a magnetic tape using a rotating head, drives the magnetic tape instantaneously and intermittently to drive the noise into the vertical retrace period while constantly recording and reproducing video signals on the magnetic tape. So-called fine slow playback, in which the vehicle is run and slow motion playback 7 is performed, is also a common technology today. As a start trigger for this intermittent drive, a magnet attached to a cylinder to which the rotary head is attached and a frequency-divided signal of a signal generated from the detection head are used. Further, the intermittent drive brake pulse is generated from a signal obtained by shifting the phase of a control signal reproduced from a magnetic tape. Here, if the switching from standard playback to slow motion playback is performed without correlation to the video track on the running tape, the noise bar cannot be brought into the vertical retrace period. Therefore, a patent has been filed which purports to perform the above switching in synchronization with the control pulse to eliminate noise bars. (Ienobu 55'5662) This example combines the present invention and the above-mentioned patent application.

The operations of the flip-flop 20, AND gate 22, etc. in FIG. 5-6 are the same as in the previous example, and the signal 24.
．． The time chart for 26.29.30 is also similar. Here, a switch 8 is used to switch between standard playback mode and slow motion playback, and a control signal is considered as the output of the pulse generator 1. Further, in FIG. 5, 66 is a start trigger for intermittent feeding, 37 is a monomulti, 38 is a motor drive circuit, and 39 is a capstan motor. As shown, the theta input of the flip-flop 35 is the Q output of the flip-flop 20. Since the signal 26 is used, the signal 40 which is the output of the flip-flop 55 becomes high for the first time at the second control signal 24 after the time 61.

The AND gate 22 passes the control pulses before time 31, and the AND gate 33 passes the control pulses Z after time 42, so the OR output of these
In other words, the output of the OR gate 34 becomes the signal 41. In this way, eliminating the control pulse at time 32 has the following advantages: During slow motion playback, the signal is fed at a slower speed than during standard playback, and stops from the point at which brake control is applied. However, when transitioning from standard playback to slow motion playback at point 32, if you suddenly pick up a control pulse and apply the brakes, the phase at which the tape stops may not be appropriate. First, a noise bar appears on the screen.In contrast, the control pulse 'k' when switching the playback mode is applied after the tape is fed at an appropriate slow speed 'm', so the noise is reduced. At the same time, as shown in the previous example, the mono multi-channel 4 can be switched at an appropriate phase and used in a time-division manner to avoid malfunctions.

〔Effect of the invention〕

According to the present invention, it is possible to realize a switching circuit that operates a monomulti multipurpose multi-purpose, time-sharing, multi-mode, malfunction-free operation, and at the same time, it can be used as a switching circuit for standard playback and slow-motion playback of a magnetic recording and reproducing device. If there is no noise,
This has the effect of allowing a smooth mode transition.

[Brief explanation of the drawing]

Fig. 1 is a block diagram for explaining the conventional example, Fig. 2 is a waveform diagram of its main part, Fig. 6 is a block diagram illustrating an embodiment of the present invention, and Fig. 4 is a waveform of its main part. 5 is a block diagram illustrating another embodiment of the present invention, and FIG. 6 is a waveform diagram of the main part thereof. 20.35...Flip-flop 21...Inverter 22.33...And gate 34...Orgate patent attorney Usui 1) Li, /1 Kimit - Figure 1 X Figure 2 (e) 15 = 0 Kaya 4

Claims (1)

[Claims] 1. Slow-motion playback is achieved by intermittently driving the magnetic tape using a control signal that indicates the track position recorded on the magnetic tape! In the magnetic recording and reproducing apparatus realized, means for switching from standard reproduction to slow motion reproduction in response to a slow command signal, means for determining the switching timing in synchronization with the control signal, and means for outputting the control signal; means for controlling slow playback using the outputted control signal, and is characterized in that only the control signal that determines the switching timing is omitted and the control signal is supplied to the slow control means. Control circuit for magnetic recording and reproducing equipment. 2. The magnetic recording and reproducing apparatus according to claim 1, wherein the slow control means is implemented by a monostable multivibrator, and the control signal is used as a starting signal for the monostable multivibrator. control circuit. '6. 2. A control circuit for a magnetic recording and reproducing apparatus according to claim 1, wherein said missing control signal is obtained by a flip-flop and a logic gate. −