JPS6381602A - Magnetic recording and erasing circuit - Google Patents

Abstract

PURPOSE:To enable a rapid and effective erasion by supplying a erasion signal having specified frequency and current value are needed to a head and erasing an FM amplification signal. CONSTITUTION:When the erasion key of an operation part 104 is operated. The movement of the head 56 in the diameter direction of a disk 60 is controlled by a control circuit 12, at the same time a switch 52 is connected to a contact point (a), the switch 45 is switched off, and moreover an FM amplifier 24 is controlled. And from the amplifier 24, the frequency is swept within the range from a first frequency which is higher than central frequency which is a low recording FM frequency to a second frequency which is higher than the maximum of the FM frequency and in the first frequency, at leas,t the erasion signal whose current is higher than the optimum recording current is supplied to the head 56, so that the respective tracks of the disk can be effectively erased in a short time.

Description

Detailed Description of the Invention (Field of Application of the Invention) The present invention relates to a magnetic recording erasing circuit for erasing signals recorded on a magnetic recording medium, and in particular, the present invention relates to a magnetic recording erasing circuit that erases signals recorded on a magnetic recording medium. The present invention relates to a magnetic recording erasing circuit that erases data in units.

[Background of the invention]

Recently, imaging devices such as solid-state image sensors and image pickup tubes have been combined with recording devices that use magnetic recording media such as magnetic disks, which are inexpensive and have a relatively large storage capacity, to take still images of subjects. An electronic still camera system has been developed in which a video signal representing the image is recorded on a magnetic recording medium, and the image is reproduced using a separate television system or printer. In addition, a magnetic recording and reproducing device has also been proposed in which a still image recorded on a visible recording medium such as ordinary film or photographic paper is photographed with a television camera, and a video signal representing the still image is recorded on such a magnetic recording medium. ing.

In these electronic still cameras and magnetic recording/reproducing devices, there is a demand for erasing a video signal once recorded on one recording unit, for example, one track, of a magnetic recording medium, and then recording the video signal on that track again.

When selectively erasing a specific track, it is conceivable to substantially erase the video signal of that track by, for example, recording an erasure signal with a higher frequency than the video signal band.

One recording method uses a band from OM Hz to 12 MHz, uses a band below 2.5 MHz for a line-sequential color difference signal, and a band above that for a luminance signal, and uses an FM modulation method to record one track per track. Recording field video signals. When erasing a track in which a video signal having such a frequency spectrum is recorded, for example, 1
It is possible to substantially erase the track by recording an erase signal of about 0 MHz for a predetermined period, and then further record an erase signal of about 20 MHz for a predetermined period. However, according to experiments conducted by the inventors, even with such a method, it is difficult to effectively erase the video signal recorded on a specific trunk, that is, to the extent that it can be rerecorded.

It has also been considered to perform erasing using a signal whose frequency is continuously changed from a low frequency to a high frequency, instead of taking such discrete frequency values. Furthermore, there is also a DC erasing method in which a DC erasing current whose polarity is reversed and whose level decreases in synchronization with the vertical synchronization signal of the recorded video signal is applied to the magnetic head. However, as is well known, signals with low frequency components magnetize a relatively deep position in the magnetic layer of a magnetic recording medium, so in order to sufficiently erase this signal, it is necessary to
A low frequency cancellation signal must be provided with a sufficiently long frequency sweep period. Therefore, it takes a long time to effectively erase the recorded video signal. For example, it takes about 1 second to erase one track recorded on a 47φ video disc, and it takes about 1 second to erase the entire trunk. It took a considerable amount of time, for example about 50 seconds, to erase all 50 lines.

[Purpose of the invention]

In view of these circumstances, it is an object of the present invention to provide a magnetic recording/erasing circuit that can erase recorded signals effectively and in a short time.

[Summary of the invention]

To achieve the above object, the present invention provides a magnetic recording erasing circuit for erasing tracks of a magnetic recording medium on which a plurality of frequency-multiplexed signals are recorded. The frequency is continuously swept in a frequency range from a first frequency higher than the center frequency of a signal with a lower frequency among the plurality of signals to a second frequency higher than the upper limit of the recording frequency band. erasing signal generating means for generating an erasing signal and supplying it to the magnetic head; It is characterized by having the following.

〔Example〕

Hereinafter, a preferred embodiment of the magnetic recording/erasing circuit according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a schematic configuration of a magnetic recording/reproducing apparatus to which the present invention is applied. In the same figure, for example, primary color signals R, G, B and a composite synchronization signal C89 output from a television camera, etc.
, are the luminance signal Y and the color difference signal R-Y by the decoder 10.
, B-Y.

The color difference signals R-Y and B-Y output from the decoder 10 are input to the FM modulator 38 via the analog switch 1.

The analog switch 1) is alternately switched every horizontal scanning period (H) by a switching pulse SP, and creates a line-sequential color difference signal based on the color difference signals RY and BY.

The FM modulator 24 is a circuit that performs FM modulation on the luminance signal Y and generates an erasure signal as will be described in detail later. The signal band spectrum is 7 MHz as shown in FIG.
Centered on, the sync chip level 26 is 6MHz,
The white peak level 28 is set to 7.5 MHz. The FM luminance signal output from the FM modulator 24 passes through a high-pass filter (HPF) 32 and undergoes frequency axis correction in a frequency characteristic correction circuit 37, and then passes through a mixing circuit 34.
is input. The frequency of the high-pass filter 32 is approximately 2.5M
It has frequency characteristics that allow signals of Hz or higher to pass through.

Further, the signal passing through the high-pass filter 32 is transmitted to the control circuit 12.
System output from? 'll signal 93 turns ON and OF
It can be bypassed by the analog switch 33 in which the F operation is performed. FM modulator 3
Reference numeral 8 performs FM modulation on a line-sequential color difference signal input via an analog switch 1). As shown in Fig. 5, the signal band spectrum is 2.5 MHz or less, and the center frequency is 1.2 MHz for the color difference signal R-Y.
The color difference signals B-Y are each set to 1.3 MHz. The FM line sequential color difference signal output from the FM modulator 38 passes through a low-pass filter (LPF) 42, undergoes frequency axis correction in a frequency characteristic correction circuit 43, and then
ON and O in response to the control signal 95 output from the circuit 12
Mixing circuit 34 via analog switch 45 operating as FF
is input. The frequency of the low-pass filter 42 is 2.5M.
It has frequency characteristics that allow signals of Hz or lower to pass through.

Note that the composite synchronization signal C5ync is transmitted to the FM modulators 24 and 38.
has been entered.

The mixing circuit 34 is a circuit that mixes the FM luminance signal output from the frequency characteristic correction circuit 37 and the FivBg sequential color difference signal output from the frequency characteristic correction circuit 43, and synthesizes it into an FM video signal for recording. The signal is input to a recording amplifier 48. Is the recording FM video signal output from the recording amplifier 48 controlled? The signal is supplied to the magnetic head 56 via an analog switch 52 which operates in response to a control signal 96 output from the II1 circuit 12.

The magnetic head 56 is supported by a head transport mechanism 58 as conceptually indicated by a dotted line 64, and is movable in the radial direction R along the recording surface 62 of the magnetic disk 60. The magnetic disk 60 is removably mounted on a rotating shaft 68 of a spindle motor 6G. The spindle motor 66 is driven by a motor drive circuit 70 and uses a frequency signal obtained from its frequency signal generator to maintain a predetermined speed, in this example 3.600. Steady rotation with pffi.

A detector 74 is arranged near the core 72 of the magnetic disk 60. This detects the timing mark formed on the core 72 and makes one rotation per rotation of the magnetic disk 60.
Generates a pulsed phase synchronization signal PG. The control circuit 12 controls the motor drive circuit 70 using this phase synchronization signal PG, and adjusts the rotational phase of the magnetic disk 60.

The magnetic head 56 is a recording/reproducing head in this embodiment, and during reproduction, the reproduced FM video signal is inputted to the reproduction amplifier 78 via the contact of the analog switch 52. The reproduced FM video signal outputted from the regenerative amplifier 78 is demodulated by a reproducing circuit 82 and then input to a video monitor device 84 . As a result, the magnetic disk 60
The FM video signal recorded on the FM video signal can be reproduced as a visible video.

Incidentally, in this embodiment, the magnetic head 56 having the reproduction characteristics shown in FIG. 2 is used. In the figure, the horizontal axis indicates frequency, and the vertical axis indicates reproduction voltage. The recording frequency band of the magnetic head 56 is approximately 0.5 MHz to 7.
．． 5MHz, and the reproduction voltage of the magnetic head 56 is F.
Approximately 1.15 mV1.1 at the center frequency (1.25 MHz) of the M-line sequential color difference signal. On the other hand, the center frequency (6.75MHz) of the FM luminance signal is about 0. 35m
V, -p. In this way, the magnetic head 56
Among the FM video signals recorded on the magnetic disk 60, the FM line sequential color difference signal is reproduced at a voltage approximately 10 dB higher than the FMff degree signal constant signal.

The reproduced FM video signal output from the reproduction amplifier 78 is also input to an envelope detector 86 that detects the envelope of the FM video signal read from the magnetic disk 60 by the magnetic head 56. The output signal is input to the control circuit 12, and the control circuit 12 can check the tracking servo of the magnetic head 56 and the recording track by controlling the head transport mechanism 58 accordingly.

The control circuit 12 supervises and controls the operation of the entire device.
The operator's instructions are input through key operations from the operation unit 104. The operation unit 104 includes, for example, a recording key for instructing recording on the magnetic disk 60, a head transfer key for instructing transfer of the magnetic head, an erase key for instructing erasure of recording, and the like.

Next, FIG. 3 shows a specific configuration of the FM modulator 24 for the luminance signal Y, and also shows a schematic configuration of the high-pass filter 32 and the frequency characteristic correction circuit 37. FM modulator 24
includes a frequency oscillator 200, which in this example is a model AN-630 supplied by Matsushita Electric Industrial Co., Ltd.
It is realized using an integrated circuit such as 6. Integrated circuit 200 includes a multi-by-break, the oscillation frequency of which depends on the capacitor C3 connected between terminals 8 and 9 and the current flowing into terminal 12.

The 1-variant signal Y output from the decoder 10 is input to the terminal 16 of the integrated circuit 200 via the capacitor C1, and the composite synchronization signal C5ync is input to the terminal 5 via the capacitor C2. Based on these signals input to the terminal 16 and the terminal 5, the integrated circuit 200 performs an FM signal as described below.
Output the luminance signal to terminal 1). This FM luminance signal is input to the base terminal of transistor Q2, thereby causing F
The M luminance signal is output to the high-pass filter 32 at the subsequent stage via a capacitor C4 and a resistor R5 connected in series to the emitter terminal of the transistor Q2. The high-pass filter 32 is configured in a π type by the coils L1 and L2 and the capacitor C5, and a resistor R18 is connected in parallel to the outside of the output side of the high-pass filter 32. Further, the cancellation signal, which will be described later, does not pass through the high-pass filter 32, and is connected to the output side of the capacitor C4 of the FM modulator 24 and the high-pass filter 32.
The signal is input to the frequency characteristic correction circuit 37 via an analog switch 33 and a resistor R33 connected to the output side of the signal. And analog switch 33
The current value of the erase signal output through the magnetic head 56
The resistance values of the resistor R5 of the FM modulator 24 and the resistor R33 are determined to be about 1.2 times or more the optimum recording current value.

A variable resistor R19 is connected in parallel to the output side of the frequency characteristic correction circuit 37, and by adjusting this variable resistor R19, the FM
The level of the luminance signal is set to be approximately 20 dB higher in voltage than the FM line sequential color difference signal.

Further, from the control circuit 12, an output permission signal 91 for permitting the output of the FM brightness signal or the erase signal output from the terminal 1) of the integrated circuit 200 is inputted to the base terminal of the transistor Q1 through the resistor R1, and further to the collector thereof. The signal is input to the base terminal of the transistor Q2 via the terminal.

As a result, when the output permission signal 90 output from the control circuit 12 becomes low level, for example, the transistor Q1 becomes conductive, and as a result, the transistor Q2 becomes cut off, so that no signal is output from the terminal 1).

The current flowing into the terminal 12 of the integrated circuit 200 is mainly caused by the conduction of the transistor Q5 through the variable resistor R6 and the resistor R7.
and variable resistance R10 and resistance R1) depending on conduction of transistor Q4. The variable resistor R6 and the resistor R7 are adjusted according to the value of the capacitor C3 so that the level 26 of the frequency signal Y becomes 6 MHz. Similarly, the variable resistor RIO and the resistor R1) are adjusted to define a difference of 1.5 MHz from 6 MHz so that the white peak level 28 of the seedness signal Y becomes 7.5 MHz.

When transistor Q5 is conductive, a current determined by variable resistor R6 and resistor R7 flows through terminal 12 of integrated circuit 200, and an FM luminance signal with a center frequency of 6 MHz is output as a sync chip to terminal 1). When the level of the luminance signal Y input from the decoder 10 to the terminal 16 of the integrated circuit 200 changes, the signal levels at the terminals 14 and 15 change accordingly, causing the transistor Q3 to conduct accordingly. In response to conduction of transistor Q3, transistor Q4 also conducts, and an output current flowing through its emitter follower (variable resistor RIO and resistor R1) is supplied to terminal 12 of integrated circuit 200. Therefore, the current flowing into the terminal 12 of the integrated circuit 200 is controlled according to the degree of conduction of the transistor Q4, and thereby the frequency of the FM luminance signal output to the terminal 1) is adjusted to the center frequency of 6 MH
z to 7.5 MHz.

By the way, at the terminal 12 of the integrated circuit 200, there is also a record (i
An integrated circuit drive circuit 202 is provided that sets the frequency of the signal used to erase the code.

The integrated circuit drive circuit 202 includes transistors Q7 and Q8, and resistors R20, R21, R22, R23, R24, and R2.
5 and a capacitor C7. The current value flowing into terminal 12 of integrated circuit 200 is
7, and in this embodiment, this terminal 1
2, set the frequency of the erase signal output from terminal 1) to approximately 7
A current is supplied to vary the frequency in the range of ~20 MHz.

Also, is there any restriction on the integrated circuit drive circuit 202? 'FII terminal 19
A low-level erase drive signal 92 having a predetermined pulse width T of, for example, about 1.5 to 2.0 seconds is supplied to this control terminal 192 from the control circuit 12. In a normal state, since the potential at control terminal 192 is set to a high level, transistor Q8 is rendered conductive. Therefore, capacitor C7, which has one end connected to the base terminal of transistor Q7 and the other end grounded, is in a sufficiently discharged state. The transistor Q8 is cut off by the low level erase drive signal 92 being supplied from the control circuit 12 to the control terminal 192, and as a result,
Capacitor C7 becomes charged. During the time it takes for this capacitor C7 to be fully charged, one end is connected to the base terminal of the transistor Q7, and the other end is connected to the power supply
The value of resistor R21 connected to cc and capacitor C7
It is determined by the time constant determined by the value of and. In this embodiment, the time constant is set to be approximately equal to or slightly shorter than the pulse width T of the erase drive signal 92.

As the capacitor C7 is charged with a predetermined time constant, the potential at the base terminal of the transistor Q7 gradually increases, and the transistor Q7 becomes conductive. This causes transistor Q7 to connect to terminal 12 of integrated circuit 200.
Then, a current corresponding to the four-way state is supplied through the resistor R20, and as the current increases, the frequency of the erase signal output from the terminal 1) gradually increases. For example, the frequency of the erasing signal output from terminal 1) of the integrated circuit 200 is
As shown in FIG. 4, the period T from time to to time L1
from about 7 MHz (first frequency) to 20 MHz
(second frequency). In this way, the first frequency of the erase signal is set to about 7 MHz, which is near the upper limit of the frequency that can be recorded by the magnetic head 56, and the second frequency is set to about 20 M f (z).

The frequency of the erasure signal is set to increase continuously in the range from the first frequency to the second frequency.

Next, the operation of the magnetic recording/reproducing apparatus having the above configuration will be described. The spindle motor 66 has a predetermined speed of 3.600 rpm.
It rotates steadily at m. In a normal state, the analog switch 52 is in the illustrated connection B (contact b). Therefore, if a video signal is recorded on the magnetic disk 60, the video is reproduced on the monitor device 84 through the reproduction amplifier 78 and the reproduction circuit 82.

Operate the head transfer key on the operation unit 104 to move the magnetic head 5.
6 is placed at an empty track position on the magnetic disk 60. This is done by the control circuit 12 controlling the head transport mechanism 58 in response to the head transport key, and whether or not the track is unrecorded is determined by the control circuit 12 via the envelope detector 86. This is done by detecting the reproduction output of the head 56.

When the magnetic head 56 is placed on the empty track, the operator operates the recording key on the operation unit 104.

As a result, first, the composite synchronization signal C5ync and the luminance signal Y outputted from the decoder 10 are FM-modulated by the FM modulator 24, and then the FM luminance signal outputted from the FM modulator 24 is processed by the high-pass filter 32 and the frequency characteristic correction circuit. The signal is inputted to the mixing circuit 34 via 37. Further, the chroma signal C1, that is, the color difference signal R- output from the decoder 10
After Y and B-Y are converted into line-sequential color difference signals by the analog switch 1), they are FM-modulated by the FM modulator 38. The FM line sequential color difference signal output from the FM modulator 38 is input to the mixing circuit 34 via the low-pass filter 42 and the frequency characteristic correction circuit 43, where it is mixed with the FM luminance signal.

In accordance with this, the control circuit 12 outputs a control signal 96 to switch the analog switch 52 from the phase synchronization signal PG to the contact point a opposite to that shown in the figure for an IV period. Therefore, the FM video signal output from the mixing circuit 34 is sent to the recording amplifier 4.
8 and an analog switch 52 to the magnetic head 56, and output it to the magnetic disk 6 as one field of video signal.
recorded on one track of 0. The reproduction output of the magnetic head 56 is output via the restored analog switch 52 (contact b).
The recorded data is visualized on the monitor device 84 via the monitor device 84, thereby allowing the recording state of the track to be confirmed.

For example, if the operator wants to delete the record after checking it on the monitor device 84, the operator operates the delete key on the operation unit 104.

In response, the control circuit 12 first outputs a control signal 96 to switch the analog switch 52 to contact a, and then outputs a control signal 95 to turn off the analog switch 45.
control so that the FM line sequential color difference signal is not input to the mixing circuit 34. and control circuit 12
From there, the FM modulator 24 receives an erasure signal 90 and an output permission signal 9.
1 and a control signal 93 are output, and an erase drive signal 92 that continues at a low level only for a predetermined pulse width T is output to the integrated circuit drive circuit 202. Furthermore, the control circuit 12 adjusts the output timing of the erasure drive signal 92 to the detection of the PG multiple signal each time to prevent switching noise from being recorded within the signal recording area of the video signal representing the image.

However, the output timing of this signal does not necessarily have to be synchronized with the PG double signal detection.

The integrated circuit drive circuit 202 receives the erase drive signal 92 and
A gradually increasing current is supplied to the terminal 12 of the integrated circuit 200 over a period T. As a result, the integrated circuit 2
An erase signal whose frequency is swept from about 7 MHz to 20 MHz over the period T is output from the terminal 1) of 00. This erase signal is sequentially supplied to the magnetic head 56 via the analog switch 33, the frequency characteristic correction circuit 37, the mixing circuit 34, the recording amplifier 48, and the analog switch 52. As a result, a current value larger than the optimum recording current value of the magnetic head 56 at the time of recording the FM video signal is superimposed on the already recorded FM video signal on the track where the magnetic head 56 is disposed. An erasure signal indicating .

Next, with reference to FIG. 6, the results when the FM video signal recorded on one track of the magnetic disk 60 is erased by this apparatus will be described.

FIG. 6 shows the frequency spectrum of the FM video signal. In the figure, the horizontal axis represents frequencies from OMHz to 10 MHz, and the vertical axis represents signal levels.

FIG. 6(A) shows the frequency spectrum of the F video signal recorded on a predetermined track before erasing. At the same mouth, centered around a frequency of approximately 1.25 MHz.

The FM chroma signal is distributed, and the FM luminance signal is distributed around a frequency of about 7 MHz. For example, an FM video signal having such a frequency spectrum as shown in FIG.
With the conventional signal erasing technology that records over 4V (V indicates one vertical scanning period) with a single frequency erasing signal of 0.7MHz, the original FM video signal is Not erased enough. In contrast, with this device, the current value of the erase signal was set to be larger than the optimum recording current value of the magnetic head, and the frequency of the erase signal was swept from approximately 7 MHz to 20 MHz, which is higher than the frequency of the FM chroma signal. In this case, the recorded FM chroma signal and FM luminance signal are sufficiently erased to a signal level that allows re-recording, as shown in FIG. 6(C). Also, Figure 6 (D
), it can be seen that substantially the same effect can be obtained even when the FM video signal is erased using a bulk eraser, which is a general demagnetizer.

As described above, the first frequency of the erase signal is set near the upper limit of the frequency recordable by the magnetic head, and the first frequency of the erase signal is set near the upper limit of the frequency recordable by the magnetic head, and By setting the value to be low, the erasing time can be shortened.

Furthermore, in this embodiment, the current value of the erase signal was set higher than the optimum recording current value of the magnetic head in the range from the first frequency (approximately 7 MHz) to the second frequency (approximately 20 MHz); however, this is not limited to this. The current value of the cancellation signal in the vicinity of the first frequency may be set high, or the current value of the cancellation signal in the vicinity of the first frequency may be set high, and then The current value may be set to decrease continuously.

Furthermore, in this embodiment, the current value of the erase signal is set to be larger than the optimum recording current value of the magnetic head when recording an FM video signal, and the frequency is set from 7°0 MHz to 20°.
Although continuously swept up to MHz, the frequency is not limited to these lower and upper limits. For example, the lower limit value may be higher or lower than the above value. Also,
It may be configured to sweep from the upper limit frequency to the lower limit frequency.

In this embodiment, a circuit for generating an erasure signal is provided in the FM modulator 24 for the luminance signal. In this case, there is an advantage that the oscillation circuit can be used for F modulation of the luminance signal, but the oscillation circuit is not necessarily limited to this, and may be provided in the FM modulator 38 for color difference signals, for example. Further, an oscillation circuit separate from these FM modulators may be provided. Note that the use of an FM modulator has the advantage that the circuit configuration does not become complicated.

〔Effect of the invention〕

As explained above, in the magnetic recording/erasing circuit according to the present invention, the first frequency is lower than the upper limit of the recording frequency band of the magnetic head and higher than the center frequency of the signal with the lower frequency among the plurality of signals. an erasing signal generating means that generates an erasing signal that continuously sweeps the frequency in a frequency range up to a second frequency higher than the upper limit of the recording frequency band and supplies it to the magnetic head; Since a current setting means is provided to set the current value of the erase signal to be larger than the optimum recording current value of the magnetic head during recording, it is effective to the level that the recorded No. 43 can be re-recorded in a short time. It can be erased automatically.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the overall configuration of a magnetic recording/reproducing device to which the present invention is applied, Figure 2 is a frequency characteristic diagram showing the reproduction characteristics of the magnetic head, and Figure 3 is for the luminance signal shown in Figure 1. 4 is an explanatory diagram showing the operation of the integrated circuit drive circuit shown in FIG. 3, and FIG. 5 is a circuit diagram showing the specific configuration of the FM modulator shown in FIG. FIG. 6 is a characteristic diagram showing an example of a frequency spectrum of a video signal, and is an explanatory diagram for showing the effect of the embodiment shown in FIG. 1. 12... Control circuit, 24.38... FM modulator, 5
6...Magnetic head, 60...Magnetic disk, 104
. . . Operation unit, 200 . . . Oscillator, 202 . . . Integrated circuit drive circuit.

Claims (7)

[Claims] (1) In a magnetic recording erasing circuit that erases a track of a magnetic recording medium on which a plurality of frequency-multiplexed signals are recorded, the frequency is lower than the upper limit of the recording frequency band of the magnetic head and the frequency is lower among the plurality of signals. Generating and supplying an erase signal to the magnetic head in which the frequency is continuously swept in a frequency range from a first frequency higher than the center frequency of the signal to a second frequency higher than the upper limit of the recording frequency band. and current setting means for setting the current value of the erasing signal at least at the first frequency to be larger than the optimum recording current value of the magnetic head during recording. . (2) Among the plurality of signals, the signal with a low frequency is a chroma signal of a video signal, and the high frequency signal is a luminance signal of a video signal.
) The magnetic recording erasing circuit described in item 2. (3) The magnetic recording/erasing circuit according to claim (1), wherein the first frequency of the erasing signal is close to an upper limit of a frequency recordable by a magnetic head. (4) The magnetic recording erasing circuit according to claim 1, wherein the first frequency of the erasing signal is selected approximately within the modulation frequency range of the luminance signal. (5) The magnetic recording/erasing circuit according to claim (1), wherein the current value of the erasing signal at the first frequency is at least 1.2 times the optimum recording current value. (6) The magnetic recording/erasing circuit according to claim (2), wherein the chroma signal is recorded with a voltage lowered by about 20 dB with respect to the luminance signal during recording. (7) The chroma signal has a band of approximately 0 to 2.5 MHz, the luminance signal has a band of approximately 2.5 to 12 MHz, and the first frequency has a band of approximately 6 to 7.
5MHz range, and said second frequency is 20MHz.
Claim No. z (
2) The magnetic recording erasing circuit described in section 2).