JPH01124135A - Rotary head type magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To suppress the fluctuation of the output voltage level of an AC coupled amplifier and to stably perform waveform arrangement by increasing a resistance value to decide the time constant of the feedback circuit of the AC coupled amplifier by a control signal to control the opening/closing of a switch which connects a control head to the AC coupled amplifier, and decreasing its amplification degree. CONSTITUTION:The charging state of a capacitor 35 changes when a first change-over switch 2 is opened. To suppress the change, a transistor 38 is turned OFF in the period of low level of a first control signal (d), and a resistor 37 is inserted in series with a resistor 36 which decides the feedback quantity of the AC coupled amplifier 30. Therefore, at the time reproducing the control (CTL) signal when the first change-over switch 2 is closed, the shift of electric charge due to the change of the charging state of the capacitor 35 at the time of opening the first change-over switch 2 can be suppressed. In such a way, since the waveform arrangement of a reproducing CTL signal during the rewrite operation of the control signal can be performed stably, it is not feared that a trouble is generated in the coding of the CTL signal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a rotary head type magnetic recording and reproducing device that sequentially records and reproduces information signals as a recording trajectory inclined with respect to the longitudinal direction of a magnetic tape using a rotary head. It is particularly unique in the control signal recording and reproducing system.

2. Description of the Related Art Conventionally, in a rotary head type magnetic recording/reproducing device, in order to obtain tracking during reproduction, a rectangular wave signal indicating the rotational phase of the rotary head during recording is used as a control (hereinafter referred to as CTL) signal to track the length of the magnetic tape. CT extending in the direction
L) Recording is performed on the rack via the CTL head.

In recent years, a technique has been put into practical use in which the duty of this rectangular-wave CTL signal is varied and recorded, and the code based on the change in duty is discriminated during playback to be used for functions such as cueing the beginning of a magnetic tape. Furthermore, a CTL signal rewriting method is being considered in which the CTL signal that has already been recorded is reproduced, coded to a predetermined duty, and then recorded on the magnetic tape again via the CTL head.
The outline is shown in Fig. 2.

In FIG. 2, the movable part 2 of the first changeover switch 2
C is connected to the CTL head 1, contact 2a is connected to the input terminal 3a of the AC coupled amplifier 3, and contact 2b is connected to the output terminal of the recording current amplifier 8. A contact 6a of the second changeover switch 6 is connected to the output terminal 3b of the AC coupled amplifier 3, and a contact 6b is connected to the reference bias power supply 4.
The movable part 6C is connected to the CT via the waveform shaping circuit 6.
It is connected to the output terminal 7 of the L signal. In addition, the above C
The output terminal 7 of the TL signal is connected to a timing pulse generation circuit 9 that performs operations described below.

The first signal generated by the output signal of the timing pulse generation circuit 9
The control signal d (FIG. 3) of the first . A second control signal e (FIG. 3) is applied as a control signal to the second changeover switch 2.5, and a second control signal e (FIG. 3) is applied to the recording current amplifier 8 as a control signal.

1o is an input terminal for an external command signal a (FIG. 3) for selecting the normal reproduction mode or rewriting mode of the CTL signal, and the applied external command signal a is applied to the timing pulse generation circuit 9.

The operation will be explained below based on the operation waveforms of the main parts shown in FIG. In the normal CTL signal reproduction mode, the external command signal is at a low level, and accordingly, the first control signal d, which is the output signal of the timing pulse generation circuit 9, is at a high level of 7. 1. The second changeover switch 2.6 is connected to the contact side of 2a and 5a, respectively, and the CTL reproduced by the CTL head of 1 is connected to the contact side of 2a and 5a.
The signal is passed through the first changeover switch 2, the AC coupling amplifier 3, and the second changeover switch 6 to the waveform shaping circuit 6.
The waveform shaping circuits input the waveform shaping CTL@C according to the rising differential waveform of the reproduced CTL signal.
The signal is outputted to the CTL signal output terminal 7 as a signal.

Next, when the CTL signal rewrite mode is entered, the external command signal a becomes high level. . When this external command signal a becomes high level, the first control signal d synchronizes with the regenerated CTL signal and moves the waveform shaped CTL signal C to a position slightly delayed from the next regenerated CTL signal. The signal changes to a signal that remains low for a predetermined period of slightly before . During the period in which the first control signal d is at a low level, the first control signal d is at a low level. Second changeover switch 2.5
are switched to the contact side of 2b and sb, respectively. That is, the CTL head 1 is disconnected from the AC coupling type amplifier 3 and connected to the recording current amplifier 8, and the reproduction CTL signal is switched from the output signal of the AC coupling type amplifier 3 to the output signal of the external bias power supply 4, and the CTL head 1 is connected to the recording current amplifier 8. The number will be rewritten.

When the CTL signal rewriting mode is entered, the second control signal e, which is the output signal of the timing pulse generation circuit 9, is synchronized with the regenerated CTL signal and has a waveform shaped CTL signal C for a predetermined period. From a position delayed by t2, the signal changes to a signal for a period t3 that ends before the next CTL signal is reproduced.

However, the pulse width of the CTL signal that has already been recorded (
This is shown in broken lines in Figure 3. ) is tl, then t ≦t
Assume that the relationship ≦(12+13) holds. When the second control signal e is applied to the recording current amplifier 8, the CTL is maintained for a period t3 of the second control signal e.
The CTL signal is rewritten by applying a recording current to the head 1 and rewriting. When a negative recording current is applied to the CTL head 1 during the period t3 of the second control signal e, the CTL signal on the magnetic tape is rewritten, and when that part is normally reproduced, it becomes as shown in Figure 3 f, and the pulse width This becomes the CTL signal at t2. In addition, a positive recording current is applied to the CTL head 1,
When that portion is normally reproduced, it becomes a CTI signal in the middle pulse layer (t2+t3) as shown in FIG. 39. Note that if the CTL signal is not regenerated at a predetermined timing, the above CTL signal rewriting operation is stopped and the first
The control signal d of is configured to be set to high level. Furthermore, the amplification degree of the AC coupled amplifier 3 constituting such a device is set to be high in order to amplify the minute reproduction signal of the CTL head.

Problems to be Solved by the Invention In such a conventional device, when the first changeover switch 2 is opened in response to the first control signal d when rewriting the CTL signal, the AC coupling amplifier 3 is opened. The DC voltage level input to the constituent operational amplifier 31 changes. Since the state of charge of the capacitor 35 constituting the feedback section AC coupling of the AC coupling amplifier 3 changes in accordance with the displacement of the DC voltage level, charge movement occurs when the first changeover switch 2 is closed. 1, CTL
The output voltage and level of the AC coupled amplifier 3 may fluctuate during signal reproduction, which may interfere with waveform shaping at the next stage.

Means for Solving the Problem In order to solve the above problems, the CTL signal rewriting device of the present invention uses a control signal created to control the opening and closing of the switch connecting the CTL head and the AC coupled amplifier.
The present invention includes means for increasing a resistance value that determines the time constant of the feedback circuit of the AC coupled amplifier and decreasing its amplification degree.

According to the above configuration, the present invention suppresses the movement of charges in the capacitor constituting the feedback section of the AC coupling amplifier when the switch connecting the CTL head and the AC coupling amplifier is opened. The state of charge of the capacitor is kept almost constant before and after the switch is opened. Therefore, even when the switch is closed, the charge on the capacitor moves only slightly, and fluctuations in the output voltage level of the AC coupled amplifier can be suppressed.

Embodiment FIG. 1 is a block diagram showing an embodiment of a recording/reproducing system of a rotary head type magnetic recording/reproducing apparatus of the present invention. Components that are the same as those in the conventional configuration shown in FIG. A resistor 37 is connected in series with the resistor 37.
A transistor 38 is connected in parallel to the transistor 38, and the first control signal d is applied to the base of the transistor 38 through a resistor 39. In the above configuration, in the normal playback mode, the first changeover switch 2 is closed and the first control signal d is at a high level, so the feedback section of the AC coupled amplifier 3o is composed of a resistor 39 and a transistor 38. The resistance value switching circuit is operated and is switched to the resistor 37. The CTL signal reproduced by the CTL head 1 is supplied via the first changeover switch 2 to an AC coupling circuit composed of a capacitor 32 and a resistor 33 of the AC coupling amplifier 30, and is connected to an operational amplifier 31 and a feedback amount. The resistance that determines 34.36
The reproduction C shown in FIG.
A TL signal can be obtained.

In addition, since the feedback section is also an AC coupling circuit, the resistor 3
The DC voltage level of the output signal of the AC coupled amplifier 3o is determined by the DC voltage level of the external bias power supply 4 supplied through the AC amplifier 3o. Next, when the CTL signal rewriting mode is entered and the first control signal d shifts from high level to low level, the first changeover switch 2 is connected to the contact 2b side, so the capacitor 32
holds the previous charge. Further, when the first changeover switch 2 is switched, the capacitor 32.3
The state of charge of 5 is balanced. When the DC voltage level input to the operational amplifier 31 changes in accordance with the opening and closing of the changeover switch 2, the state of charge of the capacitor 35 changes when the changeover switch 2 is opened. In order to suppress this change, in this circuit, the transistor 38 is turned off during the low level period of the first control signal d,
A resistor 36 that determines the amount of feedback of the AC coupled amplifier 3o.
A resistor 37 is inserted in series with. By setting the value of the resistor 37 to a large value, the amount of charge movement of the capacitor 36 is minimized, so that when the next CTL signal is reproduced, the first changeover switch 2 switches to the contact 2a@l.
At this point, the state of charge of capacitor 36 is approximately in equilibrium with that of capacitor 32. Therefore, when reproducing the CTL signal when the first changeover switch 2 is closed, charge movement due to a change in the state of charge of the capacitor 36 when the first changeover switch 2 is opened is suppressed, and the AC coupled amplifier Fluctuations in the output voltage level of 3o are suppressed and stable waveform shaping can be performed.

Effects of the Invention As described above, according to the configuration of the present invention, the waveform shaping of the reproduced CTL signal can be performed stably during the rewriting operation of the CTL signal, so there is no possibility that coding of the CTLi signal will be hindered. It is also useful in improving the reliability of cueing functions using the code discrimination, and is extremely useful in practice.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the main parts of a rotary head type magnetic recording and reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a block diagram showing the main parts of a conventional rotary head type magnetic recording and reproducing apparatus,
FIG. 3 is an operational waveform diagram of the main parts of the device. 1... Control head, 2, 6...
・Selector switch, 4...Reference bias power supply, 6
... Waveform shaping circuit, 8 ... Recording current amplifier, 9 ... Timing pulse formation circuit, 3o
・・・・・・AC coupling amplifier. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 3

Claims (1)

[Claims] A control head for recording and reproducing a rectangular waveform control signal of a predetermined duty synchronized with the rotational phase of the rotary head during recording on a control track on a magnetic tape; and a control head connected to the control head via a first changeover switch. an AC coupled amplifier; a second changeover switch that selectively switches the output of the AC coupled amplifier and the output of the reference bias power source to an output terminal;
In the rewrite mode, a control signal synchronized with the playback control signal is created, and the first and second changeover switches are controlled by the control signal, so that a predetermined number of switches before and after the playback control signal is generated is generated. control means for guiding the reproduction control signal to the output terminal via the AC coupling amplifier only for one period; and only for a predetermined third period within a second period excluding the first period. means for applying a recording current generated in synchronization with the reproduction control signal to the control head; and increasing a resistance value that determines a time constant of a feedback circuit of the AC coupled amplifier only during the second period; A rotating head type magnetic recording and reproducing device comprising means for reducing the amplification degree of an AC coupled amplifier.