JPS6180502A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To suppress a transient generated in a video signal by performing selective switching to operation states in which rotary magnetic heads are placed in recording mode at the same time, in reproducing mode at the same time, and in recording mode and playback mode respectively. CONSTITUTION:The rotary magnetic heads 22a and 22b are provided, and a magnetic tape is wound around a rotary cylinder to overlap recording type recording and reproduction. Recording amplifiers 15a and 15b and reproducing amplifiers 24a are provided for the respective heads 22a and 22b. Changeover switches S13a and S13b distributer a recording signal according to a control signal from a logical circuit 39 controlled by a system controller 40 and S25a and S25b separate a reproducing video signal and a PCM sound signal with head switching pulses from a servo circuit 28. Buffer amplifiers 14a and 14b are operated in recording mode, the recording and reproducing modes of the heads 22a and 22b are set by S16a, 17a, and 18a, and 16b, 17b, and 18b, and a transient generated in the video signal is suppressed.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] A so-called overlap recording method is developed in which a track on which a PCM audio signal is recorded is formed on the extension of a track on which a video signal is recorded. The present invention relates to a magnetic recording/reproducing device.

[Background of the invention]

In a helical scan type magnetic recording and reproducing device using two rotating magnetic heads, a magnetic tape is wound around a rotating cylinder equipped with a rotating hunting head at an angle sufficiently larger than 180° for magnetic tape, and the winding is at an angle of 180 degrees. 1 of them
Within a range of 80 degrees, the two rotating hunting heads are used to alternately record and play back video signals, and for the remaining windings, within an angular range, these rotating heads are used to alternately record digital signals such as PCM audio signals. Magnetic recording and reproducing devices that record and reproduce video signals and reproduce digital signals in this manner are known as overlapping recording devices.

According to this overlap recording method, the winding of the magnetic tape around the rotary cylinder is given by the angle θ, (
rx 7) that two rotating magnetic heads are simultaneously scanning the magnetic tape in the range of θ-180°). Therefore, when the -10,000 rotating magnetic head scans the magnetic tape by 180° winding angle, the other rotating magnetic head starts scanning the magnetic tape, and the rotating cylinder further rotates by (θ - 180'). Then, the -10,000 rotary magnetic head finishes scanning the magnetic tape.

Therefore, after the rotating magnetic head starts scanning the magnetic tape (θ-180°), digital signals are recorded and reproduced while scanning for each color, and during the next 180° winding, scanning is performed for each color. By recording and reproducing the video signal during the recording and reproducing process, continuous video signals can be recorded and reproduced without interruption (alternately recording and reproducing) through two rotating magnetic heads, similar to a normal helical scan type magnetic recording and reproducing device. In this case, the digital signal is an intermittent signal, but if this digital signal is a PCM audio signal, it is divided into sections according to the time required for half a rotation of the rotating cylinder, and the time axis is compressed for each section. This is an intermittent signal.

FIG. 11 is a diagram of a trunk pattern on a magnetic tape using such an overlamp recording method, where l is the magnetic tape, 2, 3.4 is a track, 5.6 is a rotating magnetic head, and 7
is a non-overlap area, and 8 is an overlamp area.

In the figure, the magnetic tape l is wound around a rotating cylinder (not shown) when the angle θ is 210'9, the magnetic tape l runs in the direction of arrow a, and the rotating magnetic head 5.6 The magnetic tape 1 is scanned in the direction of the arrow as a force.

Each track 2,3.4 formed on the magnetic tape 1 consists of a non-overlap area 7 and an overlamp area 8, and the overlamp area 8 is formed by the rotating magnetic head 4,
5 starts scanning the magnetic tape 1 at 30° (=2”1
The area with a width of 0'-180') is formed during scanning by an angle and is the area where digital signals are recorded.The non-overlapping area 7 is the area where the rotating magnetic head 4.
The wrap around 00 is an area that is formed during scanning by an angle and in which a video signal is recorded.

By the way, in such an overlap recording method, the digital signal is recorded in a separate area from the video signal on the magnetic tape, so especially when the digital signal is a PCM audio signal, after-recording (hereinafter referred to as "kP") is used. As disclosed in Japanese Patent Laid-Open No. 8A57-190476, one method for this is to reproduce a video signal recorded on a magnetic tape and reproduce the image on a monitor. Methods of recording audio signals are known.

In this conventional technology, when recording a video signal and a PCM audio signal simultaneously, both rotating magnetic heads 5 and 6 are set to the recording mode, and when reproducing a video signal and a PCM audio signal simultaneously, In this case, both rotating magnetic heads 5#6 are set to the playback mode, or when performing PCM post-recording, if the rotating heads 5 and 6 are scanning non-overlapping areas, the playback mode is set. When the video signal is played back and the overlamp area is scanned, the recording mode is set and the PCM
An audio signal is recorded.

Therefore, when performing PCM post-recording, the respective rotary magnetic heads 5 and 6 are necessarily switched from the recording mode to the reproduction mode during the period of scanning the tracks 2, 3 and 4. - When supplying recording blood flow to the rotating magnetic heads 5 and 6, it is common to remove the direct current component, and when the reproduction signal from the rotating magnetic heads 5 and 6 is supplied to the preamplifier, Because it is necessary to fix the reference Z ffl k and make effective use of the dynamic range,
It is common to remove heat from the @ current component from the reproduced signal, and for this purpose a capacitor is provided after the recording amplifier and before the preamplifier.

However, as mentioned above, PCM dubbing operation 11, ¥
When the rotary magnetic head 5.6 is switched between the recording mode and the playback mode, the above-mentioned capacitor is charged and discharged in accordance with this switching, and the PCM audio signal to be recorded and the reproduced video signal are thereby charged and discharged. A transient occurs in
There was a drawback that their S/N ratio deteriorated.

[Purpose of the invention]

The purpose of Fukomon is to eliminate the drawbacks of the above-mentioned conventional technology, suppress the transients that occur in the recorded digital signal during after-recording and the video signal to be played back, and to improve the appearance of the digital signal JP video signal. N'l? L: A magnetic recording and reproducing device using an overlamp recording method that made it possible to secure 1,000 digits! 1. Be willing to offer.

[Summary of the invention]

In order to achieve this object, the present invention provides a recording amplifier and a reproduction preamplifier independently for each rotating magnetic head, and also provides a switch for switching between a recording mode and a reproduction mode independently of the rotating magnetic head. It would be possible to selectively set the respective operating states in which the heads are simultaneously in recording mode and simultaneously in playback mode, one in record mode and the other in playback mode, and the operation can be performed independently between the rotary Tamaru heads. By making it possible, the record was 4m.
The feature is that it suppresses the transients of the signal and the reproduced signal.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a block diagram (not shown) of an uninvented anger recording and reproducing device, in which 9.10 is an input terminal, LL, L.
2 is an adder, 13a, Lab&X changeover switch, 14a
, 14b is a buffer amplifier, 15a and 15b are recording amplifiers, and 16a and 16b.

17a, 17b, 18a, 18b are open/close switches, 19
a, 19b, 20a, 20b are capacitors, 21
a, 21b are rotary transformers, and 22a.

22b is a rotating magnetic head, 23a and 23b are capacitors, 24a and 24b are 4X preamplifiers, and 25a.

25b is a changeover switch, 26 is a PCM sound p signal processing circuit, 27 is an LPFC low-pass filter], 28 is a servo circuit, 29 is a BPF (band caliper filter), and 30 is an F
M audio signal processing circuit, 31 is a video signal processing circuit, 32 is a capstan motor, 33, 34, 35 is an output terminal, 3
G, 37.3EH engineering input terminal, 39 is logic circuit, 4
0 (Niji system controller, 41a, 41d, 42 are inverters.

In the first □□□, rotating magnetic hands 22a, 22b
6 corresponds to the rotating magnetic head 5.6 in Fig. 11.
One, Panfa amplifier 14a, recording amplifier 15a! The buffer amplifier l 4 b , the recording amplifier 15b and the capacitor 19b constitute four recording signal processing circuits of the rotating magnetic head 22b.゛Also,
The capacitor 23a and the preamplifier 24a are configured in the reproduction signal processing circuit of the rotating magnetic head 22a, and the capacitor 23b
The preamplifier 24b constitutes a reproduction signal processing circuit for the rotating magnetic hand 22b.

The changeover switches 13a and tab are controlled by control signals Big 1 and 2 from the logic circuit 39, and distribute the recording signal to the rotary magnetic heads 22a and 22b, which scan the magnetic tape (not shown). The changeover switches 25a and 25b are connected to a servo circuit 28 that controls the camp stan motor 32 and cylinder motor (not shown).
The video signal and P are drawn by the spider head switching pulse and reproduced from the rotating magnetic heads 22a, 22b.
Distinguish between CM audio and CM.

The buffer amplifiers 14a and L4b are controlled by the control signal Sig3 of the logic circuit 39, and are activated when the rotating magnetic heads 22a and 22b are in the recording mode, and are inactive when they are in the reproduction mode.

The on/off switches 16a, 17a+18m are used to set the recording/reproduction mode of the rotating magnetic head 22&, and the on/off switches 16a, 17a, 17m are used as logic circuits 39.
The open/close switch 18a is controlled by a control signal Si,4 obtained by inverting the control signal 51g4 with an inverter 41m.

Open/close switch 16&.

17m is closed and the open/close switch 18a is opened, the rotating magnetic head 22& is set to the recording mode. Conversely, the open/close switches 16m and 17a are opened and the open/close switch 18m is switched to the recording mode.
By closing the rotary head 22, the rotary head 22 enters the playback mode. Open/close switch L6b.

17b and tab are also used to set the recording and reproducing modes of the rotating magnetic head 22b, and are connected to the logic circuit 39.
(More specifically, the open/close switch 18b is controlled by the control signal Stg5 obtained by inverting the control signal 55g5'r inverter 41b), and the open/close switches 16b, 17b are closed. When the open/close switch 18b opens, the rotating magnetic head 22
b is in the recording mode, the on/off switches 16b and 17b are opened, and the on/off switch 18b is closed, so that the rotating magnetic head 22b is in the reproducing mode.

Further, from the logic circuit 39 to the PCM audio signal processing circuit 2
6 is supplied with a control signal Sig 6, which causes the PC to
The M audio signal processing circuit 26 is switched between recording operation status and reproduction operation status.

The system controller 40 generates a recording operation command signal REC and a reproduction operation command signal PR'PPCM dubbing command signal Ars+e by operating an operation panel (not shown), and the logic circuit 39 generates these command signals and the head switching pulse AJPPCM audio signal. From the overramp period signal B generated by the processing circuit 26, the control signal Sig l
- Form Sig 6. In addition, overramp signal B
is a signal representing period 7 during which the rotating magnetic heads 22a and 22b scan the overlap area 8 (FIG. 11),
It is formed based on the head switching pulse A. In addition, the recording operation, playback operation, and PCM dubbing operation are simply class A of the operations of this embodiment as a whole, whereas the recording mode and playback mode are, as is clear from the previous explanation. , a rotating 8-air head 22a.

22b.

Next, the operation of this embodiment will be explained using the timing chart 7 of FIG. 2, dividing it into recording operation, reproducing operation, and PCM post-recording operation.

(1) During recording operation At this time, the recording operation command signal RFC generated by the system controller 40 is at a high level (hereinafter referred to as 'H'), and the reproduction operation command signal PB and pcyx dubbing operation command signal 7kree are at a low level. level (hereinafter referred to as "L").As a result, the control signal Sig 3 from the logic circuit 39 becomes "L", and the banfa amplifier 14m
, 14b are set to the active state. , and the control signal S
ig 4 becomes "H", opening/closing switches 16a, 17
a is closed, the open/close switch 18m is opened, and the rotating magnetic head 22a is in the recording mode. Similarly, the control signal Sig 5
becomes H#, the open/close switches 16b and 17b are closed, the open/close switch 18b is opened, and the rotating magnetic head 22b enters the recording mode. Further, the control signal 81% becomes "I(", and the PCM audio signal processing circuit 26 is set to the recording operation state.

10,000, the head switching pulse A is generated during the 'L' period Tl' when the rotating magnetic head 22a is moving in the non-overlamp area 7 (FIG. 11). 'Yes, rotating air outlet head 22
When b is scanning into non-overlapping area 7, "
H “period 1 alT 2 raro. See you soon.

The overlap period signal B is the 'H' period T3 when the rotating magnetic head 22a is scanning overlapping area 8 (ITT diagram), and is in the 'H'' period T3 when the rotating magnetic head 22b is scanning overlap area 8 (Fig. , 'H' period T4, and @H# period T3 is the head switching pulse A.
After the ``H'' period T2, ``H# Kanma T4 is also L.
``The timing coincides with the latter part of period T1.

The control signals Sig l and Sig 2 are used for head switching/?
It is formed from pulse A and overlap period signal B.

Control signal Sig 1 is “°” of overramp period signal B.
H” period i'tiiT3. In other words, the rotating magnetic head 22
The control signal Sig2 becomes H' only during the period when m scans the overlamp area 8, and the control signal Sig2 becomes the overlamp period signal B.
"H# period T4", that is, "H#" and r only during the period when the rotating magnetic head 22b scans the overlamp area 8.
x The changeover switches 13a and 13b each receive a control signal S.
ig l, Sig 2 closes to the contact A side during the 'H# period, and closes to the contact B side during the 'L1 period.

Now, the first audio signal is supplied from the input terminal 36, and is FM modulated by the FM audio signal processing circuit 30.
In addition, a video signal is supplied from the input terminal 37, and the video signal processing circuit 31 separates the brightness signal and chroma signal from the video signal.The brightness signal is FM-modulated and the chroma signal is converted to a low frequency signal. Furthermore, a second
The audio signal is supplied, PCM modulated by the PCM audio signal processing circuit 26, and subjected to time axis compression to form the intermittent signal described above.

Here, the FM audio signal processing circuit 30 adjusts the FMR to 1kAFM, and the video signal processing circuit 31 receives the FM
The modulated luminance signal YFM, the chroma signal which has been low frequency converted, is represented by C, and the second audio signal, which has been PCM-modulated into an intermittent signal by the PCM audio signal processing circuit 26, is represented by APCM. In addition, the servo circuit 28 is missing a pilot signal for tracking control, which is indicated by the pilot signal P.

The APCM signal generated in the PCM audio signal processing circuit 26 and the P signal generated in the THERM circuit 28 are added in an adder 11, and the output signal of this adder 1'l (APCM $p
)c However, e represents the addition of the signals. ] is supplied to the contact A of the changeover switches 13a and 13b. Further, the C signal generated in the video signal processing circuit 31, the P signal generated in the THERM circuit 28, and the AIPM signal generated in the FM audio signal processing circuit 30 are added, and this added signal (C$P IE
BAFM) is added to the YFM signal generated by the video signal processing circuit 31 in the Calo calculator 12. The output signal (Y, MfBC89PRA, M) of the adder 12 is transferred to the selector switch 1.
It is supplied to contact B of 3a and 13b.

The changeover switch 13a switches the contact A during the period when the rotating magnetic head 22a scans the overlap area 8 (FIG. 11).
Contact B is closed to allow the output signal (ApcM$p) of adder 11 to pass through, and the contact B is closed to pass the output signal (ApcM$p) of adder 11 for the rest of the period.
Let the output signal (YFMeC PeAIPM) pass through. These signals that have passed through the changeover switch 13a are sent to the balagua amplifier 14a and the recording amplifier 1 as the recording signal S.
5m, and after removing the flow component of the hun hun sa 19a''ri, the open/close switch 16a and the capacitor 20a1
Stator side of rotary transformer 21a, open/close switch 1
Flows into the ground terminal via the 711 flame. At this time, the current 1a flowing to the stator side of the rotary transformer 21m or the rotating magnetic head 22a via the rotary transformer 21ak.
be transmitted to. As a result, the non-overlapping area 7Vc image signal, I9 pilot signal and FM audio signal of every other track 2 and 4 shown in FIG. .

On the other hand, the changeover switch 13b is set during the period in which the rotating magnetic head 22b scans the overramp area 8.
When the contact A is closed, the output signal of the adder 11 (A, .M$P
) Pass the fire, other periods, '19 = a, B g
A! l K closed-c-hly, passing the vessel 12 mm force signal (YFM@CeP6) A, M). These signals that have passed through the changeover switch 13b are amplified as a recording signal Sb by a buffer amplifier 14b and a recording amplifier 15b, and after the DC component is removed by a capacitor 19b, they are transferred to an open/close switch 16b and a capacitor 20b.

The positive stator side of the rotary transformer 21 is connected to the ground terminal via the open/close switch 17bχ. At this time, the current ib flowing to the stator side of the rotary transformer 21b is directly transmitted to the magnetic head 22b via the rotary transformer 21b'.
transmitted to. As a result, the adder 12 is placed in the non-overlapping area 7 of every other trunk 3 shown in FIG.
The output signal < y, t9c$p69AyM) is written fi
The output signal (A, .M6)P) of the adder 11 is recorded in the over 5 area 8.

Here, open/close switches 16a, 16b, 17a.

17b+18g=18b are each electronic switch
・In this case, the open/close switch 16
DC components generated in capacitors 20a and 20
b, and a rotating magnetic head 22a.

22bVC @ 1,000 times to prevent current from flowing. Further, in general, the rotary magnetic heads 22a, 22b require an optimum current recording current of about 20 to 30 mA, and to satisfy this, the recording amplifiers 15a, 15b are provided with a sufficiently large drive capacity. Furthermore, the buffer amplifier 14
a, 14b is the output DC voltage V with the control signal Sig 3
1r V 2 is controlled and the control q+Ejsig3 is n
When L#, the recording amplifier 15a.

DC voltage v1 is large enough to drive 15b.

Output v2.

(2) At this time, the reproduction operation command signal PR generated by the system controller 40 is H", and the recording operation command signal RE
C and PCM dubbing command <a number Ar0° should be L#. As a result, the control signal S of the logic circuit 39
ig 4 and Sig 5 are set to "L#". For this reason, the open/close switch 16 m + 17 a is opened, the open/close switch 18 a is closed, and the rotating magnetic head 22A enters the playback mode. Similarly, the open/close switch 1. 16b,
17b is opened, the open/close switch tab is closed, and the rotating magnetic head 22b is also placed in the reproduction mode. In addition, the control wart No. Si
g6 becomes L11, and the PCM audio signal processing circuit 26
is set to playback mode.

The signals reproduced by the rotating 'di-isolation heads 22a and 22b are as follows:
Rotary transformer 2 L a * 2 L b
.

Passes through capacitors 23a and 23b'r, preamplifier 24
m, Shun amplified by 24b, both changeover switch 25
m, supplied to 25b. The selector switch 25a is
je circuit 28 or head switching) 9 Lus Avc! The cutoff switch 25b is controlled by the pulse A which is inverted by the inverter 42 and the head switching pulse 25b is controlled by f1%.

As a result, the changeover switch 25a closes to the contact A side to pass the output signal of the preamplifier 24a and rotate While the head 22b is scanning the non-overlapping area 7, the contact B is closed to allow the output signal of the preamplifier 24b to pass through. On the other hand, the changeover switch 25b closes to the contact A side and switches on the preamplifier 24a during the period when the rotating blood/blood head 22a is away from the @air tape and during the period when the overlap area 8 (Fig. 1L) 7 is being scanned. Pass the output signal,
Period 1 when the rotating magnetic head 22b is away from the magnetic tape
(2) While scanning the overlap area 8 and 1, the contact B is closed to allow the output signal of the preamplifier 24b to pass through.

The signal C obtained from the engineering switch 25m in response to the operation of the changeover switches 25a and 25b is a continuous signal (YFM69113PEA, M) formed by the adder 12, and the signal C obtained from the changeover switch 25b is a continuous signal (YFM69113PEA, M) formed by the adder 12. This is an intermittent signal (APCM P) generated by the device 11.

The signal C is supplied to the video signal processing circuit 31, where the YPM signal and the C signal are separated and converted into their original signals to form a video signal, which is output to the output terminal 34. In addition, the signal C is supplied to the BPF29 to separate the A7 signal, and the F
It is FM demodulated by the M audio signal processing circuit 30 and sent to the output terminal 33.
supplied to Furthermore, the signal C is also supplied to the LPF 27 to separate the P signal, which is processed by the servo circuit 28 to perform tracking control of the rotary magnetic heads 22a #22b by phase control of the capstan motor 320.

-1, the signal from the changeover switch 25b is PCM-1
The iP signal processing circuit 26 separates the APCM signal, which undergoes processing such as time axis expansion and 20M demodulation to become a continuous second audio signal, which is output to the output terminal 35.

Here, if the pan amplifier 14 a r 14 b s recording amplifier 15 ae 15 by 11 is kept in the same state as during recording operation, even if the open/close switches 16 a, 16 b are open, the recording amplifier 15 a, 15 b Ki will be 10 to 2.
'gLR of about 0 mA is the power supply, ground terminal 'sir:B
As a result, there is a possibility that a signal may be excited on the long side of the preamplifiers 24&, 24b, and since the gains of the preamplifiers 24m, 24b are very high, this may cause oscillation of the circuit. For this reason, during the reproducing operation, the control signal 1g3 from the logic circuit 39 is set to H'', and the buffer amplifiers 14m, 14
The output surface current voltage Vt*Vz"ff of b is sufficiently lowered, and the operation of the recording amplifier 15 a hl 5 b O) is stopped.

(3) During PCM dubbing operation At this point, the PCM dubbing operation command signal 80 generated by the system controller 4o is 'H#' and the recording operation command signal REC is L1. Furthermore, as explained above, since the PCM audio signal is recorded while monitoring the PCM dubbing playback picture 1:j:,
It is normal to switch from the reproduction operation state to the PCM post-record operation state, and moreover, during the PCM-after-record operation, the reproduction circuit must be operated at all times. For this,
During PCM dubbing operation, the playback operation command signal PB is also “
Let it be H#.

That is, when both the PCM dubbing operation command signal Area and the playback operation command signal PB are "H", the PCM
The dubbing operation status is set.

As a result, the control signals Sig 1 and Sig 2 generated from the logic circuit 39 are the same as during the recording operation,
There is a changeover switch 13a for the scanning position of the rotating magnetic heads 22a and 22b on the magnetic tape.

The switching timing of 13b is the same as that during recording operation, but the control signal Sig 3 is switched to the rotating magnetic heads 22a, 22.
The period during which b scans the overlamp area 8, that is,
Period T3*T during which overlap period signal B is “H”
4, it becomes L", and in other periods, it becomes H". For this reason, the buffer amplifiers 14a, j4 only during these periods.
Increase the output INK voltage Vt, V2'+r of b, put recording 77 f15 a, 15 b into the operating state, and during the remaining period, avoid the interference from the recording system side to the reproducing yarn side as explained earlier. I have to.

9B Control signal S generated from logic circuit 39
ig 4 is H' during the period T3 when the rotating magnetic head 22a scans the overlamp area 8. During the period T3 of the overlamp period signal B, the on/off switch 16a is , 17m are closed and the open/close switch 18m is opened, and the rotating magnetic head 22a is in the recording mode.
a, 17a, and 18a are in the opposite state, and the rotating magnetic head 22m is in the reproduction mode.

The control signal Sig5 is 1H during the period when the rotating magnetic head 22b scans the overlap area 8, that is, the overlamp period signal B OJ'H is 1H only during the period T4, and as a result, the rotating magnetic head 22a and Similarly, the rotating magnetic head 22b is in the recording mode during the period when it scans the overlamp area 8, and is in the reproduction mode during the remaining period.

Furthermore, the control signal Si generated from the logic circuit 39
g 6 becomes “IHJI”, and PCM audio signal processing circuit 2
6 is set to the recording operation state.

Furthermore, the changeover switches 25a and 25b perform the same switching operation as in the reproduction operation in response to the head switching pulse A.

Therefore, when the rotating magnetic head 22a scans the overlamp area 8, the changeover switch 13a is closed to the contact A side, and the output signal of the adder 11 is N A , (MIEE)P)
A recording signal S is supplied to the rotating magnetic head 22a and recorded in the overlamp area 8. Similarly, the output signal (AFM P) of the adder 11 is recorded in the overlamp area 8 by the rotary magnetic head 22bK.

Signal recorded in non-overlamp area 7 (YF
M CAP A □) is a rotating magnetic head 22a, 22b.
The signal C is alternately reproduced by the changeover switch 25a, as in the reproduction operation, and becomes a continuous signal C. This signal C is processed in the same manner as during the reproduction operation, and an image is reproduced on the monitor.

When the rotating magnetic heads 22a and 22b are running in the overshift area 8, the IC is activated by the open/close switch 17a.
, 17b is closed and the playback mode VC is on, so no signal can be obtained from the open/close switch 25b. Furthermore, when the rotary 8-air heads 22m and 22b are in the recording mode, the other one is in the playback mode. Non-overlamp area 7 is being scanned for missing playback. Therefore, either the recording destination 13 (or +b) flowing to the rotary transformer 21a (or 21b) of the rotary magnetic head 22a (or 22b) (1411) in the recording mode or the rotary magnetic head 22b (or 22a) in the reproduction mode ) leaks into the rotary transformer 21b (or 21a), causing crosstalk in the reproduced signal.CN in the signal CIC from the changeover switch 25a is this crosstalk component.

FIG. 3 is a block diagram showing a specific example of the logic circuit 39 in FIG. 2, in which 43 to 48 are AND gates, 49 to
51 is an OR circuit, and 52 and 53 are inverters.

This logic circuit, shown in FIG. Each of the control signals Sig 1 to 51g6 is generated by the following calculation process.

Sig　　　　=A-B s+g2=”’i-B 51g3=PR-A -100 eC Sig 4=RE C+Sig l・Are.

Sig 5=REC+Sig 2・AreaSig 6
= Rk, C+A, .

As described above, in this embodiment, fi regular recording is performed.

In addition to playback, you can also perform PCM dubbing.

By the way, during the PCM dubbing operation, the rotating magnetic head 22 a e 22 b does not switch from the recording mode to the playback mode or from the playback mode to the recording mode. Capacitor 19 provided for removing DC component
It is possible that charging and discharging occurs in a, 19b-IP con f7 20 a * 20 b, and this causes the recording of 4g.
Transients occur in the signal and the reproduced video signal, causing S/N deterioration wE of the PCM audio signal JP and the reproduced video signal. However, the above embodiment solves this problem, and transients during PCM post-recording operation do not pose a problem.

This transient problem will be explained below with reference to FIG. 4, which specifically shows the mounting section of FIG. 1. naυ, 4th
In the figure, 54 to 60 are input terminals, 61.62 are output terminals, and the KIS corresponding to FIG. 1 lacks the same sign.

In FIG. 4, the input terminal 54 is connected to the input terminal 7'1.
4a (Fig. 1), the human power horse 55 is connected to the Banfa amplifier 14b (Fig. 1), and the input terminal 56
A control signal SIg3 obtained by inverting the previous control signal SigB is supplied. l, input terminal 57.58
are supplied with optical control signals Sig 4 and Sig 5, respectively, and input terminals 59 and 60 are connected to inverters 41a and 41, respectively.
b (Figure 1) is connected to the large control/official name Sig 4
, Sig 5 will be supplied. Furthermore, output terminal 61.
62 are both selector switches 25 a # 25 b (
It is connected to the 1st Ward 1).

Transistor Q1 constitutes on-off switch 16a in FIG. 1, and its base is connected to input terminal 57 via resistor R3, and its collector is connected to capacitor 19a.
, its emitter is connected to capacitor 20a and further to resistor R2.
It is connected to the. The transistor Q'+ constitutes the open/close switch 16b in FIG. 1, and its base is connected to the input terminal 58 via a resistor R'3, its collector is connected to a capacitor 19b, and its emitter is connected to a capacitor 2ob and a resistor Rl. are connected to each other. irs, the transistor Q3 constitutes the closing switch 17□a of the circuit 11, and its pace is connected to the input cam element 57 through the resistor Rs k valve, and its collector is connected to the rotary transformer 21a and the capacitor 23a. At the back of the connector, the 0 emitters are connected to the ground terminal, respectively. Transistor Q'3 is the first
The opening/closing switch consists of 1 switch and 7 bases are resistors R.
It is connected to the input terminal 58 through '5'/-, its collector is connected to the connection point between the rotary transformer 21b and the capacitor 23b, and its emitter is connected to the ground terminal.

Furthermore, the transistor Q2 is connected to the first open/close switch 1
The pace is connected to the input terminal 59 through the resistor Ri', and is also grafted to the capacitor C4, whose collector is 7 a%. ``20a, so-
The emitters of each are connected to the ground terminal. The transistor Q'2 is connected to the input terminal 60 through the resistor I','4', and is also connected to the capacitor CI4.
ht, its collector is conf/s20blC1
Its emitter is connected to the ground terminal.

In this configuration, the transient when the rotary magnetic head 22a switches from the reproduction mode to the recording mode during the post-recording operation will now be described.

As soon as the rotating loss head 22n is in the playback mode R, the transistor Q2 is on and the transistor QllQS is off, and the potential at point F at this time is N (Vl
It is. At the moment when the rotating magnetic head 22a switches from the reproduction mode to the recording mode, transistors Q1+Q3 are turned on, transistor Q2 is turned off, and transistor Ql is turned on.
The base 'C4K charges the capacitor 20m, and a transient of the recording signal 5 occurs until this charging is completed. The charging time constant of this capacitor 20a is C2·R3, where its capacitance is C2, and this time constant t
By reducing Zk, it is possible to suppress transient loss of recording current ia.

2. Capacitor 19 m + 20 m is recording current 1
This is a factor that determines the low frequency cutoff frequency of 8, and limits their capacity. - 10,000, the recording amplifier 15a is provided with a coil LX and a resistor R1 in parallel between the collector of the transistor Q4 to which the recording signal of the input terminal 54 is supplied and the power supply terminal to which the power supply voltage vec is applied;
The parallel resistance value (Rx/Rz) of this resistor R1 and the resistor R2 connected to the emitter of the transistor Qr acts as a damping resistance value that flattens the frequency characteristics of the recording amplifier 15a in a required frequency band. Therefore, the resistance value of resistor R1 cannot be kept too small. Specifically, the frequency characteristics of the recording amplifier 15a vary from the stator side of the rotary transformer 21a to the rotating magnetic head 22a.
ll'f? If the inductance seen by f is LH, then the parallel inductance (Lf/LH) of this inductance L and the inductance of the coil LX, and the transistor Q
Determined by the resonance characteristic due to the stray capacitance C generated on the emitter side of t and the parallel resistance value (R1/R1) of the damping resistor R1 + R2 (1'), Tatoe, L, = 56
μH%LH=9μI(,R,=1・2,Ω,R,=2・
7 is Ω, the frequency characteristic of the recording current la is 10MH
It can be flattened to about z.

By the way, in order to turn on the transistor Q1, 1! flows through the resistor R2! The size of the current cannot be made very large (specifically, about 1 mA).

From the above, restrictions are added to the resistance value of resistor R3,
I can't stay too small.

However, within the above-mentioned constraints of the capacitor 20a and the resistor R3, by making the charging time constant 02.Rs't' as small as possible, the record 1! Transients of flow ia can be suppressed sufficiently small.

Furthermore, if the transistor Qlk is not provided, when the rotating magnetic head 22m is in the reproduction mode, the capacitor 19m is discharged via the transistor Q2 which is turned on, and the rotating magnetic head 22m is switched to the recording mode and the transistor Q2 is turned on. When turned off, since the capacitor 9a is charged, a transient occurs in this charging period record tit. However, in this embodiment, when the rotary magnetic head 22m is in the reproducing mode, the transistor Ql is off, so the capacitor 19a cannot be discharged, and the charge in the recording mode is retained. Therefore, even when the rotating magnetic head 22m switches from the reproduction mode to the recording mode, there is no need to charge the capacitor 19a, and no transient occurs due to the capacitor 19m.
By charging only the capacitor 20m and making the charging time constant k sufficiently small as described above,
Be able to keep the recording to a sufficiently low level of Flow 18's transient fire.

Next, the transient loss of the reproduction signal when the rotary male head 22a switches from the recording mode to the reproduction mode, the fifth
This will be explained using FIGS.

FIG. 5 does not show the reproducing system of the rotating magnetic head 22a of FIG. 4, and in this case, the input stage of the preamplifier 24a is specifically shown with transistors Q6, Qt, a load resistor R8, and a constant voltage source 63. The same applies to the parts corresponding to Figure 4.
The sign is missing.

In FIG. 5, when the rotating magnetic head 22a is in the recording mode, the transistor Q2 is off, and if its collector potential is V, the voltage across the charged capacitor 20a is V, as shown in the figure. Point F (
The potential of the collector of transistor Q3 is zero M. In addition, generally, the input stage of the preamplifier is a transistor Qa
, Qy.

It has a cascode configuration including load resistor R8 and constant voltage weight 63, and the second place at point G (base of transistor Q7) is 78 g. For this purpose, capacitor 2
As shown in 1, 3a is charged and the voltage across it is vB.

Therefore, when the rotating magnetic head 22a switches from the recording mode to the reproduction mode, the transistor Q! turns on and transistor Q3 turns off, so the collector voltage of transistor Q2 becomes zero (■), and the potential at point F drops by a voltage of V to -V, as shown in Figure 6. Accordingly, the potential at point G also changes to i pressure vr, as shown in FIG.
and becomes -(V, -VBI). Thereafter, the potentials of the capacitors 20a and 23a at point F and point G become zero, respectively.
V) % V, and converges to a steady state.

On the other hand, as shown in FIG.
(The 4th @ is not provided, therefore, the capacitor 2
0a (Fig. 4) is provided between the rotary transformer 21a and the collector of the transistor Q3, and the transistor Q is provided on the base side of the transistor Q7.
3 & on and off (generally, this is the conventional configuration), when the rotating magnetic head 22a is in the recording mode, the transistor Q! is off and transistor Q3 is on, so the collector potential of transistor Q2 is 1, and the potential at point H on the rotary transformer 21a side of capacitor 23a is v.

Since the voltage IE at one point at the base of the transistor Q7 is zero M, the capacitor 23m is charged as shown, and the voltage across it is vr.

Therefore, when the rotating magnetic head 22a switches from the recording mode to the reproduction mode, the transistor Q2 is turned on and the transistor Q3 is turned off, so that the voltage at the H point σJ instantaneously changes to v
It drops by r and becomes zero (B), and along with this, the potential at one point also drops by ■ and becomes 1. Thereafter, the capacitor 23a is charged until the potential at point I (σ-) reaches a steady value of vB, and during this time a transient occurs in the reproduced signal.

Comparing the transients in the circuit configurations of Figures 5 and 7, we find that in the circuit configuration of Figure 5, the potential at point G changes from -(V, -VBr, ) to A transient occurs while vBgVc changes, and the amount of change in potential during this period is vBF, +(v.

−vBE)=vr. For this: rL, in the circuit configuration of FIG. 7, as shown in FIG. 8, the potential at point H is
Vr to v! During the change to 1E, there is a transient transition, and the amount of change in potential during that time is (V, , +Vr). Therefore, in the circuit configuration shown in FIG. 5, the potential change from the time of switching from the recording mode to the reproduction mode until the preamplifier 24a reaches the steady operating state is small, and the transient period is shortened accordingly.

As described above, the transient during the PCM post-recording operation can be suppressed to a sufficiently low level, and can be made equivalent to the S/Ny11-reproducing operation of the PCM audio signal or the reproduced video signal. The above explanation is based on the rotating magnetic head 22a.
The same applies to the rotary 8-air head 22b side.

Although the above has been related to transients, the circuit configuration shown in FIG. 4 further provides the following impressive effects.

First of all, the optimum recording current for the rotary magnetic heads 22a, 22b is about 20 to 30 mAp-p.
A DC current of about 15 mA is applied to prevent distortion and black deterioration of the recording current. Therefore, recording amplifier 15
The current flowing into the ground terminal of m, 15b is very large.

Therefore, the emitter of transistor Q41Q'4 is connected to resistor R
When the transistor Q41Q'4 is grounded through s*R'6 and the current is always flowing through the transistor Q'2, this DC box, θIL, is connected to the recording amplifier. It is directly connected to the transistor Q'z through a common impedance between the ground point of the transistor Q'x and the ground point of the transistor Q'x. Also, when transistor Q2 is on, transistor Q'4
The direct current flowing into the transistor Q2 flows through the common impedance Q) between the ground point of the recording amplifier 15b and the ground point of the transistor Q2. At this point, when a disturbance signal such as a power supply ripple is superimposed on the DC current of the recording amplifiers 15a and 15b, the disturbance signal generated in the impedance (approximately 40) between the collector and emitter of the turned-on transistor Qz+Q'z. As a result, the S/N ratio of the output signals of the reproduction preamplifiers 24a and 24b is extremely degraded.

In order to prevent this, in the recording amplifier 15g + 15b, transistors Qs+Q's are connected to the emitters of transistors Q4 and tQ'4, respectively, and the emitters of these transistors Qs+Q's are grounded, and the bases of these transistors Q5+Q's are connected to each other. A control signal obtained by inverting the previous control signal Sig3 is connected to the input terminal 56. A41 signal Sig 3 is supplied.

As shown in FIG. 2, the control signal Sig3 is "L" only when the rotating magnetic heads 22a, 22b are in the recording mode, but the control signal 51g3 is low only when the rotating magnetic heads 22a, 22b are in the recording mode.
22b becomes H" only when in the recording mode, and only in this case, the transistor Qs r Q's is turned on. Therefore, the rotating magnetic head 22a.

Transistors Qs+Q's are off except when 22b scans the overlamp area 8 (FIG. 11), and no direct current flows through the recording amplifiers 15a and 15b, resulting in deterioration of the S/N of the output signals of the preamplifiers 24 and 24b. can be avoided.

Second, in the recording amplifiers 15a and 15b, in order to prevent the collector potential of the transistor Q4IQ'4 from fluctuating as the transistors Qs+Q's turn on and off, the connection between the collector of the transistor Q4aQ'4' and the power supply terminal is A coil L1 + L'l is provided between them to avoid a resistive load and use an inductance load. Also, the transistor Qt
If +Q't is not provided, the transistor QzeQ
When 'z is turned on and the rotating magnetic heads 22a and 22b are in the reproduction mode, power ripple leaks into the respective reproduction systems via the coil ``!, capacitor 19a, and also via the coil L'1 and capacitor 19b. .

However, in this example, the transistor Qz rQ'
+ is provided, and when the rotating magnetic heads 22a and 22b are in the reproduction mode, these transistors Q1゜Q't&
It is possible to prevent power supply ripple from leaking from the recording system to the reproduction system due to the occurrence of τ in the off state, and the S/N of the reproduction signal is improved.

Furthermore, by shutting off the rotating hunting heads 22a, 22b that are connected to the recording amplifiers 15a, 15b except during the recording mode, the amount of military power consumed can be significantly reduced.

^9 Figure 9 is a circuit diagram showing the main part of another embodiment of the quick recording/reproducing capacitor according to the present invention, in which the rotary magnetic head 22a side corresponds to the end part shown in Figure 4, and the other parts are the part shown in FIG. It has the same configuration as in Figure 1. In FIG. 9, parts corresponding to those in FIG. 4 are given the same reference numerals.

In this embodiment, the transistor Q1 in the specific example shown in FIG. 4 is omitted, and the transistor Q8 lQ is used instead.
9 is provided to cause the capacitor 20a to be charged, released, and fired instantaneously, thereby almost eliminating transients.First, the operation in the case where the transistor Qs=Qi is not provided will be explained.

In this case, there is no transistor Ql, and the capacitor 19m and transistor Q! The configuration is the same as that shown in FIG. 4 except that a resistor R11l is provided between the connection point with the collector and the power supply terminal.

When switching from the reproduction mode in which transistor Q2 is on and transistor Q3 off to the recording mode in which transistor Q2 is off and transistor Q3 is on, capacitors 19a and 20a are connected to resistor R16 by the flow 11 shown by the dashed line. The charging time constant at this time is
Resistor R111 and capacitor l 9 a.

The parallel capacity fr of 20 m is determined by Ct/C. Therefore,
In order to reduce this charging time constant, is it better to reduce the resistance value of resistor R16 and the resistance of capacitor 19a?
Since a and 20a define the low cutoff frequency of the recording current, and the resistor R1 defines the flatness of the frequency characteristics of the recording current, their values are restricted and the charging time constant The lower limit is restricted, making it difficult to suppress transients.

On the other hand, in this embodiment, a PNP type trunk xlQ6 is provided between the collector of the transistor Q2 and the power supply terminal, and the pace of the transistor Q8 is connected to the input terminal via a differentiating circuit consisting of a resistor R11 and a capacitor C5. 5
In addition, a PNP type transistor Qs'I- is connected between the collector of the transistor Q3 and the ground terminal, and the input terminal 57 is connected to the input terminal 57 through a differentiating circuit consisting of a resistor R11l and a capacitor C6, which is the base of this transistor Qs. The capacitor 20a is charged and discharged instantaneously by turning on the transistor Qs=Qs, and the resistor R
The redundant current at 16 is used to charge capacitor 19a, thereby quickly suppressing the transient.

Next, using the time chart in Figure 10, capacitor 2
The charging and discharging of 0a will be explained in more detail.

Assuming that the rotating magnetic head 22& is now in the reproduction mode, the transistor Q2 is on, the transistor Q3 is off, and the capacitor 20m is hardly charged.

Therefore, the control signal Sig 4 is "H", and the control signal Sig 4 is set to "H".
becomes L# and the rotating magnetic head 22a enters the recording mode, the transistor Q2 is turned off and the transistor Q3 is turned on. However, at the falling edge of the control signal Sig4 from the input terminal 59, a negative voltage is applied to the Y point by the differentiating circuit. 9rus occurred,
This /4 pulse is supplied to the pace of transistor Q8, turning on transistor Qs. For this reason, t Rl□ shown by a solid line flows through the transistor Qs1 capacitor 20a, the rotary transformer 21a, and the transistor Q3, and the capacitor 20a is instantaneously charged by this current 12. The charging time Ta at this time is the capacitor Cs
is set by resistor R11. Therefore, the large current flowing through the resistor R16 is used only for charging the capacitor 19&, and the charging time for the capacitor 19m is also significantly shortened.

In this way, the transients of the recording signal will be significantly suppressed.

Next, when the rotating magnetic head 22m switches from the recording mode to the reproduction mode, the transistor is activated. 2 is inverted from off to on, and transistor Q3 is inverted from on to off, but at the same time, the control signal Si from the input terminal 57
At the falling edge of g4, a negative pulse is generated at the point X by the differentiating circuit, and this negative pulse turns on the transistor Q9. For this reason, due to the charge accumulated in the capacitor 20a, the discharge current Bi2 shown by the solid line is increased by the transistor Q
s, rotary transformer 21a, capacitor 20a,
) 61 through transistor Q2 Y, capacitor 20
a is momentarily discharged. The discharge time T6 at this time is determined by the capacitor C6 and the resistor Ris.

At this time, the capacitor 19m is also instantaneously discharged, and the collector potential of the transistor Q2 instantaneously becomes steady state.

In this manner, this embodiment can eliminate the factors that inhibit the shortening of the charging time constant of the capacitor 20a, and can instantaneously perform the warpage charging 11, thereby suppressing transients to a greater extent.

Although the explanation has been made regarding the rotating magnetic head 22a side, the same applies to the rotating magnetic head 22b side. Further, in the above embodiment, the digital signal is a PCM audio signal, but other digital signals such as an image information signal may be used.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to significantly suppress the transients of recording signals and playback signals during PCM dubbing operation, and to generate PCM audio signals and It is possible to provide a magnetic recording and reproducing device that can obtain video signals and has excellent functions by eliminating the drawbacks of the prior art described above.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the magnetic recording/reproducing device according to the present invention, FIG. 2(2) is a timing chart showing signals of each part in each operating state of the first prisoner, and FIG.
A block diagram showing a specific example of the logic circuit in Figure 4 is a block diagram showing a specific example of the logic circuit in Figure 1. Figure 6 is a circuit state diagram for explaining the transient at
An explanatory diagram showing the change in viewing position at a predetermined position in the figure. An explanatory diagram of the potential fluctuation at a predetermined position in the figure, FIG. 9 is another implementation of the magnetic recording and reproducing apparatus according to the present invention?
Figure 10 is a timing chart for explaining the transient suppression effect in Figure 9.
FIG. 11 is a schematic diagram showing a trunk pattern on a 1MI party tape using the overlap recording method. 11, 12...adder, 13 a, l3
b - Selector switch, 14m, 14b... Banfa amplifier, 15a, 15b... Recording amplifier, 16a, 16
b, 17a, 17b, 18a18b - open/close switch, 1
9a, 19b, 20a, 20b-capacitor, 21a121b... rotary transformer,
22a, 22b... Rotating hunting hend, 23a, 23b
... Capacitor, 24a, 24b - Preamplifier, 25a, 25b... Selector switch, 26...
- PCM audio signal processing circuit, 31... video signal processing circuit, 39... logic circuit, 40... system controller. Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Procedural amendment export) March 7, 1985

Claims (1)

[Claims] In an overlap recording type magnetic recording/reproducing device comprising at least two rotating magnetic heads and in which a magnetic tape is wound around a rotating cylinder over an angle sufficiently larger than 180°, each of the rotating magnetic heads A recording amplifier and a reproducing preamplifier are provided independently for each disc, and a switch is provided for independently switching the rotating magnetic head to a recording mode or a reproducing mode. 1. A magnetic recording/reproducing device characterized in that it is configured to be selectively switchable between operating states, one being a recording mode and the other being a reproducing mode.