JPS61211856A - Control signal reproducing device - Google Patents

Abstract

PURPOSE:To reproduce an accurate control signal by switching at least one of an input resistor of an amplifier and a load resistor depending on a time corresponding to a specific position of a tape to converge the mean DC value of the reproducing signal in a shorter time. CONSTITUTION:A control circuit 8 outputs an output pulse S3 corresponding to a specific position on a tape by an output signal S2 and FG signal obtained from a pulse generator 7 and representing the running amount of the tape. The switches 12, 16 are turned on when the signal S3 is at H level and in this case, resistors 10, 11 and resistors 14, 15 are connected in parallel respectively. Thus, the mean DC value of the reproducing signal is converged rapidly according to the time constant when the switches 12, 16 are connected is set smaller than the time constant decided by the reproduced signal waveform and the tape lower limit speed, thereby reducing the period until the output signal S2 of the comparator 3 outputs again a pulse corresponding to a reproduced CTL signal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a two-baso control signal reproducing apparatus for reproducing control signals (CTL signals) recorded on a magnetic tape such as a video tape.

Conventional Technology As a means for reproducing control signals (hereinafter referred to as CTL signals) recorded on magnetic tape, a so-called alternating current (AC) coupling method is used, in which a coupling capacitor is provided in the input circuit to cut the DC component. Amplification devices are commonly used.

In recent years, in video tape recorders (hereinafter referred to as VTft) that record and reproduce image signals on magnetic tape, the tape speed during playback has been adjusted to be faster, slower, or faster than the speed during recording.
The speed is variable, such as stopping, and a noise-free screen is reproduced at any speed.

VTRs equipped with so-called automatic tracking devices have been put into practical use.

In these VTRs, the absolute position of the tape is detected and the scanning locus of the reproducing head is controlled thereby to obtain a noise-free screen. Therefore, in order to detect the absolute position of the tape, the CTL signal recorded on the tape is
Must be reliably reproduced and detected at all speeds.

3.- Hereinafter, an example of the above-mentioned conventional control signal reproducing device will be described with reference to the drawings. FIG. 4 shows an example of the main circuit configuration of a conventional control signal reproducing device, and FIG. 5 shows an output signal S4 of the amplifier 23 and an output signal S5 of the comparator 24 in FIG.

First, the output signal of the CTL signal reproducing head 22 is transmitted to the capacitor 28 (C3) provided at the input of the amplifier 23, and the resistor 2
9(R6) [fo-1/(2
The output signal of the amplifier 23, from which the following components are removed and amplified by the amplifier 23, has a frequency [f1=1/(2π04R6)] further determined by the capacitor 3o (C4) and the resistor 31 (R6). ] The following components are removed and input to the controller 24. The converter 24 has an internal reference voltage v2 as shown in FIG. (hereinafter referred to as L) is output as shown at 85 in FIG. Therefore, by detecting the rising or falling edge of the output S5 of the comparator 24, the CTL signal on the tape can be detected. The lower limit of the frequency is determined by f and fl, and ○ Since the reproduction frequency of the CTL signal is proportional to the tape speed,
To regenerate the CTL signal when driving at low speed, f □ *
It is necessary to set f 1 sufficiently low with respect to the reproduction frequency of the CTL signal. Inversely proportional to that, the time constant τ
3[-1/(2π, fo)], τ4[-1/(2πf1
)] becomes larger.

Therefore, when the power is turned on or when tape running restarts from a stopped state, the time constant τ. , τ1, the average direct current (DC) value of the reproduced signal converges to a constant potential, so the fifth
As shown in the figure, the comparator 24 operates for a certain period t (seconds).
, it becomes impossible to output a pulse corresponding to the reproduced CTL signal, and as the lower limit of the reproducible frequency becomes lower, t also becomes longer.

5. In view of the above problems, the present invention provides a time constant τ3.tau at a time corresponding to a specific position on the tape according to the running of the tape.
The present invention provides a control signal reproducing device which can shorten the time required for the average DC value of a reproduced signal to converge to a constant potential by switching τ4, thereby reproducing a CTL signal more accurately. be.

Means for Solving the Problems In order to solve the above problems, the control signal reproducing apparatus of the present invention includes an amplifier circuit for amplifying a CTL signal recorded on a magnetic tape, and an amplifier circuit for amplifying a CTL signal recorded on a magnetic tape, and a pulse generator that outputs pulses corresponding to the traveling distance; and a pulse generator provided in at least one of the input circuit and the output circuit of the amplifier circuit,
and input resistance.

Alternatively, a second resistor connected in parallel with the first resistor that determines the load resistance, a switch that can connect and disconnect the second resistor with respect to the first resistor, and the switch. , to a control port 6 which is controlled to turn on and off at a time corresponding to a specific position on the magnetic tape using the output pulse of the pulse generator.

According to the above-described configuration, the present invention switches at least one of the input resistance or the load resistance of the amplifier circuit at a time corresponding to a specific position on the tape, thereby amplifying a necessary control signal and at the same time As in the case where the constant is set small, the average DC value of the reproduced signal is converged in a shorter time, thereby enabling accurate reproduction of the control signal.

Embodiments Hereinafter, control signal reproducing apparatuses according to embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a block diagram of an embodiment of the invention.

In FIG. 1, 1 is a CTL signal reproducing head, 2 is an amplifier, 3 is a comparator, 4 is a magnetic tape, 5 is a capstan shaft, 6 is a pinch roller, 7 is a pulse generator, and 8 is a switch 12.16. Control circuit for on/off control, 9
'13 is a coupling capacitor (C1) that cuts the DC component of the input signal of amplifier 2, and '13 is a coupling capacitor (C2) that cuts the DC component of the output signal of amplifier 2.
), 1o is the input resistance of amplifier 2 (R1), 14 is the load resistance of amplifier 2 (input resistance R3 of comparator 3), 11
゜16 are connected to resistors 10 by switches 12 and 16, respectively.
．． 14, and their respective resistance values are R2 and R4.

FIG. 2 shows an example of the pulse generator 7 that outputs pulses depending on the amount of tape travel. In the figure, 17 is a magnetic tape, 21 is a capstan motor that drives the running of the magnetic tape 170, 19 is a rotating disk attached to the rotating shaft of the capstan motor 210, and 18 and 20 are rotating disks 19.
This is a slit on the top or a detector that detects magnetic signals. The magnetic tape 17 is pressed onto the rotating shaft of the capstan motor 210 by a pinch roller (not shown), and runs according to the rotation of the capstan motor 210, and a number of pulses corresponding to the number of rotations of the rotating disk 19 are output from the detectors 18 and 20. is output. Rotating disk 19
As the detectors 18 and 20 may be well-known ones, a detailed explanation thereof will be omitted here.

FIG. 3 is a timing chart showing signal waveforms of each part of the control signal reproducing device of the present invention. In FIG. 3, Sl
is the input signal to the comparator 3 in FIG. 1, and S2 is the output signal of the comparator 3. vl is the reference voltage preset in comparator 3, S3 is switch 1
This is an output signal of the control circuit 8 that controls on/off of each switch 12.2.16, and when it is at H (High) level, each switch 12.
16 is turned on.

The operation of an embodiment of the control signal reproducing device of the present invention will be described below with reference to FIGS. 1, 2, and 3.

In FIG. 1, the control circuit 8 is obtained from the output signal S2 of the comparator 3 and the pulse generator 7.

A pulse S3 corresponding to a specific position on the tape is output from the FG multiplied signal indicating the amount of tape travel. Switch 12.1
6 is turned on when the S3 signal is at H level. Therefore, the pulse S
When 3 is at H level, resistors 1° and 11, resistors 14 and 15
are connected in parallel, respectively, so the time constants are also τ4=C1×R1×R2/(R1+R2)τ;=C2×
R3×R4/(R3+R4). Here, as shown in Fig. 3, the Norculus S3 is set to be at H level at a timing corresponding to an unnecessary portion in the reproduced signal waveform, that is, at a time corresponding to a specific position on the tape. As a result, the respective time constants τ4. τ; can be freely set.

Therefore, for the time constants τ1-C1・R1, τ2-C2・R3 determined by the playback signal waveform and the lower limit of the tape speed, the time constant τ4 when the switch 12.16 is connected
．． If τ is set sufficiently small, the average DC value of the reproduced signal will quickly converge, and the output signal S of the converter 3 will be
2 can shorten the period until it outputs a pulse corresponding to the reproduced CTL signal.

Effects of the Invention As described above, according to the present invention, the required re-101,
- An excellent effect can be obtained in that the missing period of the reproduced signal caused by the time constant determined by the lower limit of the raw horse wave number can be shortened while maintaining the lower limit of the reproducible frequency.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a configuration diagram showing an example of a pulse generator used in the present invention, and Fig. 3 shows signal waveforms and timing of each part in the embodiment of the present invention. FIG. 4 is a block diagram of the conventional example, and FIG. 6 is a diagram showing signal waveforms and timing of each part of the conventional example. 1... Head for control signal reproduction, 2...
Amplifier, 3...Comparator, 4...
Magnetic tape, 5... Capstan shaft, 6...
...Pinch roller, 7...Pulse generator, 8.
... Control circuit, 9, 13 ... Coupling capacitor, 10, 11 ... Input resistance, 12
．． 16...Switch, 14.15...Load resistance 0 Agent's name Patent attorney Toshio Nakao and 1 other person - S % ~) Shitsumo)

Claims (1)

[Claims] an amplifier circuit that amplifies a control signal recorded on a magnetic tape; a pulse generator that outputs pulses corresponding to the amount of travel of the magnetic tape; and at least an input circuit and an output circuit of the amplifier circuit. A second resistor provided on one side and connected in parallel with the first resistor that determines the input resistance or load resistance, and the second resistor is connected or disconnected from the first resistor. A control signal reproducing device comprising: a switch that can be set to a state; and a control circuit that controls the switch to be turned on and off at a time corresponding to a specific position on a magnetic tape using an output pulse from the pulse generator.