JPH11273183A - Method and device for rotational magnetic recording/ reproducing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To switch an opposing head by a method capable of eliminating the necessity of a switching circuit provided on a drum. SOLUTION: This rotational magnetic recording/reproducing device is provided with at least a pair of magnetic heads 11, 12 and 11', 12' connected in series, rotary drums 10 and 10' at which at least a pair of magnetic heads is opposedly arranged to each other, and tapes are wound with specified angles, and a permanent magnet 14 arranged to cover a circumference other than the side of winding the tape 15 of the rotary drum by a specified angle by keeping a certain distance for providing a magnetic field to saturate one or the other of the pair of magnetic heads. The active states of the opposing magnetic heads are switched alternately. Thus, the numbers of channels and circuits for the rotary transformer of a rear stage are reduced by half, and unnecessary power consumption is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rotary magnetic recording / reproducing apparatus and a rotary magnetic recording / reproducing method, and can be applied to, for example, a rotary magnetic head of a video tape recorder (hereinafter, VTR).

[0002]

2. Description of the Related Art A VTR using a rotary magnetic head uses a rotary transformer as a means for transmitting a signal between the rotary magnetic head and a signal processing circuit when recording or reproducing a video signal. Usually, the number of stages of the rotary transformer is increased in accordance with the number of heads to be used. In this case, the limit is about eight steps due to installation conditions and cost conditions. There is also a double structure having 16 steps.

When the diameter of the drum provided with the magnetic heads facing each other is large, a switching circuit for the magnetic head is provided on the drum to save the number of rotary transformer stages. As such an example, Japanese Patent Application Laid-Open No. 1-260601 discloses that a reed switch is arranged on a rotating drum, and a control signal is applied to this reed switch to a coil which is fixed externally and is adjacent to the reed switch, thereby providing a magnetic field. A rotary head type magnetic recording / reproducing apparatus that switches a transmission path between a head and a rotary transformer by generating a signal and switching a reed switch is disclosed.

FIG. 8 shows a conventional head switching using a photo MOS head switch at the time of recording and erasing. In FIG. 8, there is a drum having a photoMOS head switch in the drum. In this case, as in the case of reproduction,
By switching the photo MOS head switch, the head is alternately switched, the recording signal supplied to the terminal 60 is amplified by the recording amplifier 61, and transmitted to the drum via the rotary transformer 62. Recording can be performed on the tape by the 63 or B head 65. A recording or erasing head having an inductance of about 0.3 μH from the transmission band is used.

At this time, an optical signal is input to the gate in the photo MOS head switch 64 or the photo MOS head switch 66 provided at both ends of the A head 63 or the B head 65 saturated by the proximity to the permanent magnet. To turn on (conduct), and the head can be switched. In this case, the resistance value when the photo MOS head switch 64 or the photo MOS head switch 66 is turned on is as large as 5 to 10 Ω, and the maximum allowable current is 100.
mA.

Further, Japanese Patent Application Laid-Open No. Hei 4-79009 discloses that
The degaussing means for erasing the magnetic head is attached to a portion of the fixed drum that does not come into contact with the magnetic tape, and the magnetic head that rotates according to the rotating drum every time the rotating drum makes one rotation is not in sliding contact with the magnetic tape. A rotating magnetic recording / reproducing apparatus is disclosed which prevents deterioration of recording / reproducing characteristics due to magnetization of a magnetic head by utilizing the demagnetization.

[0007]

However, in the above-mentioned conventional rotary head type magnetic recording / reproducing apparatus, since the head is switched in the drum, first, it is necessary to supply a circuit power supply. It is necessary to transmit a DC voltage using a slip ring or a brush, or to transmit the DC voltage using a power rotary transformer and rectify the DC voltage. Second, it is necessary to transmit a switching signal. Therefore, when supplying a signal of the number of switching channels, it is necessary to demodulate in a drum when performing modulation multiplex transmission. Third, an area for mounting the switching circuit is required on the drum, and therefore, in addition to the switching circuit, an area for arranging a preamplifier, a recording amplifier, the above-described demodulation circuit, a power supply circuit, and the like is required. However, there is a disadvantage that the diameter of the drum must be increased in order to satisfy such a condition.
In addition, the conventional photo MOS at the time of recording and erasing shown in FIG.
In the case of head switching using a head switch, since the resistance value at the time of switch-on is large, there is a disadvantage that the S / N is reduced.

In the DV (digital video) format, the recommended drum diameter is as small as 21.4 mm, and it is difficult to satisfy the above-mentioned conditions. (In this case, if the tape pattern is the same, the drum diameter is arbitrary, but the recommended diameter is appropriate for miniaturization.)

The quadruple speed VTR has two channels for an erase (ERS) head, four channels for a recording (REC) head, four channels for a reproduction (PB) head, and a DV reproduction (D
VPB) The head has four channels and a total of 14 channels. As a function, normal recording or reproduction, video editing, audio, and pre-read editing are possible, but dynamic tracking (recording simultaneous reproduction and variable speed reproduction, which are almost all mounted in a VTR for a broadcast station). DT) No playback function is installed.

In order to perform simultaneous recording and reproduction, an additional four-channel head is required. In addition, the function of the dynamic tracking reproduction cannot be mounted because the current drum diameter is small, so it is conceivable to perform the non-tracking reproduction by adding four more heads.
To satisfy all of the above, a total of 22 channels of heads are required.

In this case, the rotary transformer can be realized by increasing the number of stages to 22 channels. However, since the number of wirings of the head and the transformer is 44 corresponding to the turn of the series circuit, the circumference of the drum is not changed. If it is assigned above, the distance between the pins of the rotary transformer is about 1 mm, crosstalk may occur, and it is difficult to arrange the switching circuit on the drum.

The present invention has been made in view of the above points, and there is no need to provide an electrical switching circuit on a drum, and a rotating magnetic recording / reproducing method and a rotating magnetic recording capable of switching between opposed heads. It is intended to propose a playback device.

[0013]

According to the present invention, there is provided a rotating magnetic recording / reproducing apparatus according to the present invention, wherein at least a pair of magnetic heads connected in series, and at least a pair of the magnetic heads are arranged to face each other. A rotating drum around which the tape is wound at a predetermined angle, and a magnetic field saturation means disposed around the rotating drum other than the side on which the tape is wound over a predetermined angle to provide a magnetic field that saturates one or the other of the pair of magnetic heads; In which the active state of the opposed magnetic heads is alternately switched.

Further, the rotating magnetic recording / reproducing method of the present invention comprises:
At least one pair of magnetic heads are connected in series, and the at least one pair of magnetic heads are arranged facing each other on a rotating drum, a tape is wound at a predetermined angle, and around the rotating drum other than the side around which the tape is wound. A magnetic field in which one or the other of the pair of magnetic heads saturates is applied over a predetermined angle to alternately switch the active state of the opposing magnetic heads.

According to the rotary magnetic recording / reproducing apparatus of the present invention,
It works as follows. The magnetic head has a narrow gap width,
Since the magnetic path near the gap is small, when a static magnetic field is given,
The magnetic flux concentrates in the gap and saturates. When the magnetic path saturates, the inductance becomes air-core and the impedance drops significantly.

For this reason, if a pair of magnetic heads facing each other are connected in series and a saturation magnetic field is applied to one or the other of the pair of magnetic heads by magnetic field saturation means, the pair of magnetic heads can be switched alternately. I can do it. If magnetic field saturation means having a timing length to be switched is provided on the circumference of the rotating drum, switching can be performed regardless of the number of magnetic heads.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the present embodiment, 180
In a small VTR having a rotating magnetic head equipped with a head opposed to each other, a magnetic field that saturates the head from outside the drum is applied by magnetic field saturation means to switch the head to be used.

First, before describing the head switching according to the embodiment of the present invention, an outline of the operation of the magnetic field saturation means of the present embodiment will be described. In FIG. 1, the permanent magnet 1 is moved from the position a to the position b of the permanent magnet 1 ′, and the head 2 (14.4 Ω / 1 MHz reproducing head: 1 MHz
Approaching 14.4Ω), the impedance Ω detected by the impedance analyzer 3 and the inductance μH determined from the impedance and the signal frequency are as follows. That is, when the measurement frequency MHz is 1.0 MHz, when the position a is sufficiently far, the impedance Ω / inductance μH is 14.3 Ω / 2.2 μH, and when the position b is sufficiently close, the impedance Ω / inductance μH is 2.0 Ω / 0. .3 μH. Also, the measurement frequency MHz
Is 10 MHz, and when the position a is sufficiently far, the impedance Ω / inductance μH is 128.2 Ω / 2.0 μ.
H, and when the position b is sufficiently close, the impedance Ω / inductance μH becomes 10.6 Ω / 0.17 μH.
When the measurement frequency MHz is 20 MHz, the impedance Ω / inductance μH is 282.0 Ω / 2.0 μH when the position a is sufficiently far, and the impedance Ω / inductance μH is 21.6 Ω when the position b is sufficiently close.
/0.17 μH.

Here, the video head for a VTR has a narrow gap width and a small magnetic path near the gap. Therefore, when a static magnetic field is applied, the magnetic flux concentrates in the gap and saturates. For this reason, the permanent magnet 1 is moved from the position a to the position b of the permanent magnet 1 '.
Up to the head 2 and saturation, the impedance Ω / inductance μH at the position b with respect to the position a becomes 1 /
It drops to about 10.

Next, FIG. 2 shows a head switching state according to the present embodiment. In FIG. 2, a tape 15 is
Is wound around a predetermined angle, but on the side where the tape is not wound, the permanent magnet 14 is arranged on the circumference of the drum 10 so as to cover the drum 10 at a predetermined distance over a predetermined angle, and faces the drum 10. The A head 11 and the B head 12 are mounted, connected in series, and connected to the rotary transformer RT13. The magnetizing direction of the permanent magnet 14 is from the north pole to the south pole or in the opposite direction in the width direction of the drum 10 (from the front to the back in FIG. 2).

Here, at the position a shown in FIG.
The head 11 is located at a position close to the permanent magnet 14, and the B head 12 is located at a position where it is in sliding contact with the tape 15. At this time, the B head 12 is performing a reproducing operation, and the A head 11 is in a (magnetic) saturation state. Position a of the drum 10 shown in FIG. 2A
When the drum 10 ′ is rotated to the position b shown in FIG. 2B, the B head 12 ′ is at a position close to the permanent magnet 14, and the A head 11 ′ is at a position where it slides on the tape 15. At this time, the A head 11 'is performing a reproducing operation, and the B head 12' is in a saturated state. Thus, the drum 1
When 0 is rotated, when the pair of opposing A heads 11 and B heads 12 approach the permanent magnets 14, they are alternately saturated, and head switching is performed. The position of the permanent magnet 14 may be a position facing the drum 10 or on a fixed drum as long as the above-described operation can be performed, and is not limited thereto.

FIG. 3 shows a head switching operation during reproduction according to the present embodiment. In FIG. 3A, at position a, the tape 2
4, the B head 20 is in the reproducing state, and the A head is in the saturated state. Therefore, when viewed from the reproducing amplifier 22, the inductance 21 (0.17 μH) of the saturated A head is obtained.
Are connected in series to the B head 20 (2 μH), and a reproduction output P / BOUT is output from the terminal 23.
Further, in FIG. 3B, at the position b, the A head 25 is in the reproducing state with respect to the tape 24, and the B head is in the saturated state. Therefore, when viewed from the reproducing amplifier 22, the inductance 26 (0. 17 μH) is connected in series to the A head 25 (2 μH).
3 outputs a reproduction output P / BOUT.

At this time, since the impedance / inductance of the head which is saturated with respect to the reproducing head only enters the series, the change in the resonance frequency is small and the S / N is not deteriorated. On the other hand, if a resistor is inserted in series, S
/ N decreases. When a pair of heads facing each other are simply connected in series, the resonance frequency is reduced to に, and the frequency characteristics (F characteristic) and S / N in a high frequency range are deteriorated.

FIG. 4 shows a diagram for measuring characteristics of the head during reproduction according to the present embodiment. In FIG. 4, the signal generator 3
0 is connected to the ground via a resistor 31 of, for example, 50Ω, the A head 32 and the impedance Z33 are connected in series, and the reproduction output amplified by the reproduction amplifier 34 is measured by the spectrum analyzer 35. According to the head characteristic measuring circuit shown in FIG. 4, the characteristic can be measured by the spectrum analyzer 35 by magnetically coupling the impedance Z33 to the A head 32 for the signal from the signal generator 30.

FIG. 5 shows a frequency characteristic (F characteristic) 40 and an S / N characteristic 41 of the head during reproduction according to the present embodiment. In FIG. 5, a characteristic 1 is a frequency characteristic when the impedance 33 in FIG. 4 is 0Ω in a directly connected state and one A head 32 is used, and a characteristic 2 is a characteristic in FIG.
FIG. 4 shows frequency characteristics when the same head as the A head 32 is connected in series, and the characteristic 3 in FIG. 4 shows that the impedance 33 in FIG. As can be seen from FIG. 5, the characteristic 3 indicating the head switching state of the present embodiment does not deteriorate compared to the characteristic 1 indicating the head switching by the switching circuit. Further, it can be seen that the characteristic 2 indicating the characteristic of simply connecting the pair of heads facing each other in series is deteriorated compared to the characteristic 3.

As described above, it has been found that there is no change in characteristics at the time of reproduction by the head switching according to the present embodiment. Further, not only the head switching at the time of reproduction described above, but also at the time of recording and erasing, the same operation is performed by the head switching according to the present embodiment, so that there is no change in characteristics. The head switching at the time of recording and erasing is the same as that at the time of reproduction, and therefore the description is omitted.

FIG. 6 shows a switching state of a plurality of opposed heads according to the present embodiment. In FIG. 6, a tape 58 is wound around the drum 50 at a predetermined angle.
7 are arranged on the circumference of the drum 50 so as to cover a predetermined distance over a predetermined angle, and the A head 51 and the A ′ head 54 facing the drum 50, the B head 52 and the B ′ head 55 and the C head 53 The C ′ head 56 is mounted, each pair is connected in series, and connected to a rotary transformer (not shown). Here, the A head 51, the B head 52, and the C head 53 each have a predetermined angle α (0
<Α <180 degrees).
The magnetizing direction of the permanent magnet 57 is from the north pole to the south pole or in the opposite direction to the width direction of the drum 50 (from the front to the back in FIG. 6).

Next, FIG. 7 shows the switching timing of such a plurality of opposing heads of the present embodiment. In FIG. 7, from 0 degrees to 180 degrees shown in FIG. 6, the A head 51 is in a saturated state (O
N), and the A ′ head 54 facing this is the tape 5
8 is in an active state (OFF) because it is in a position where it slides. Further, from 0 + α to 180 + α, the B head 5
2 is in a saturated state (ON) because it is located close to the permanent magnet 57, and the B ′ head 55 opposed thereto is in an active state (OFF) because it is in a position where it slides on the tape 58. From 2α degrees to 180 + 2α degrees, the C head 53 is in a saturated state (ON) because it is in a position close to the permanent magnet 57, and the C ′ head 56 opposed thereto is in a position where it slides on the tape 58. Active state (OFF).

The drum 50 is moved from the position shown in FIG.
When rotated by 80 degrees, the A head 51 is in the active state (OFF) from 180 degrees to 360 degrees shown in FIG. It is in a saturated state (ON) because it is at a position close to 57. From 180 + α degrees to α degrees, the B head 52 is in the active state (OFF) because it is in a position where it slides on the tape 58, and the B ′ head 55 that faces the B head 52 is in a position that is close to the permanent magnet 57. It is in a saturated state (ON). From 180 + 2α degrees to 2α degrees, the C head 53 is in the active state (OFF) because it is in the position where it slides on the tape 58, and the C ′ head 56 that faces the C head 53 is in the position that is close to the permanent magnet 57. It is in a saturated state (ON).

When the drum 50 is rotated in this manner, a pair of A heads 51 and A 'heads 54, B
Head 52 and B 'head 55 and C head 53 and C'
As the head 56 approaches the permanent magnet 57, it alternately saturates,
Head switching is performed. The position of the permanent magnet 57 may be at a position facing the drum 50 or on a fixed drum, as long as the above-described operation is possible, and is not limited thereto.

As described above, switching of a plurality of opposing heads can be performed by a single permanent magnet 57 without requiring any complicated timing signal. At this time,
The timing of switching between the saturated state (ON) and the active state (OFF) of the head is indicated by an angular display of the rotational movement of the head according to the time.

In this case, the tape 58 for the drum 50
If the effective winding angle is 180 degrees or less, the operation can be performed without any problem. However, considering the effects of the tape guide and the permanent magnet 57 for winding the tape 58 around the drum 50 and the influence of the switch operation, 150 degrees or less is practical. Yes,
At this time, it is necessary to make the drum diameter 1.2 times or more corresponding to the tape winding angle reduction ratio of 180/150 degrees.

If the magnetic field of the head is saturated with the permanent magnet 57 for a long period of time, magnetism may become a problem. ), N, S in the width direction of the drum 50
Subsequently, permanent magnets for demagnetization which alternately repeat N, S... Are arranged in a strip shape and are magnetized on the head. Can be demagnetized.

In the rotary magnetic recording / reproducing apparatus according to the present embodiment, at least one pair of magnetic heads connected in series and at least one pair of magnetic heads are arranged to face each other.
A rotary drum around which the tape is wound at a predetermined angle, and a rotary drum is arranged so as to cover at a predetermined distance over a predetermined angle around a side other than the side on which the tape is wound, and a magnetic field in which one or the other of the pair of magnetic heads is saturated. A permanent magnet as a magnetic field saturation means is provided, and the active state of the opposing magnetic heads is alternately switched.By switching the opposing magnetic heads, the number of channels of the subsequent rotary transformer can be reduced by half. By reducing the number of channels by half, the number of recording, reproducing and erasing circuits can be halved. Further, since no switching circuit is provided in the rotating drum, there is no need to supply power to the switching circuit, and the circuit switch By eliminating unnecessary power consumption, low cost and low power consumption It is possible to obtain a recording and reproducing apparatus.

In the rotary magnetic recording / reproducing apparatus according to the present embodiment, the permanent magnet as the magnetic field saturation means is provided over the timing length at which the magnetic head is to be switched. Can be switched with a simple configuration using a single magnetic field saturation unit.

In the rotary magnetic recording / reproducing apparatus of this embodiment, the active state of the opposing magnetic head is reproduction, recording, or erasure in the above description. The switching operation of the magnetic head can be performed.

In the rotary magnetic recording / reproducing method according to the present embodiment, at least a pair of magnetic heads are connected in series, and at least a pair of magnetic heads are arranged on a rotating drum to face each other. One or the other of the pair of magnetic heads applies a magnetic field that saturates the periphery of the rotating drum at a predetermined angle over a predetermined angle around the other side of the rotating drum except the side where the tape is wound. Since the states are alternately switched, the number of channel processes of the subsequent rotary transformer can be halved by switching the magnetic heads facing each other, and the recording, reproducing and erasing processes can be performed by halving the number of channel processes. Because it can be halved and does not switch within the rotating drum,
There is no need to supply power for the switching process, circuit switching is not required, and unnecessary power consumption is eliminated, so that low power consumption can be achieved at low cost.

In the rotary magnetic recording / reproducing method according to the present embodiment, the saturation magnetic field is applied over the timing length at which the magnetic head is to be switched. Can be performed with a simple process by only a single process that saturates the magnetic field.

In the rotary magnetic recording / reproducing method of the present embodiment, the active state of the opposing magnetic head is reproduction, recording, or erasure in the above description. The switching operation of the magnetic head can be performed.

[0040]

According to the rotary magnetic recording / reproducing apparatus of the present invention, at least one pair of magnetic heads connected in series,
The at least one pair of magnetic heads are arranged facing each other,
A rotating drum around which the tape is wound at a predetermined angle, and a magnetic field saturation means disposed around the rotating drum other than the side on which the tape is wound over a predetermined angle to provide a magnetic field that saturates one or the other of the pair of magnetic heads; Since the active state of the opposing magnetic heads is alternately switched, the number of channels of the subsequent rotary transformer can be halved by switching the opposing magnetic heads. The recording, reproducing and erasing circuits can be halved, and there is no switching circuit in the rotating drum, so there is no need to supply power to the switching circuit, and no circuit switches are required, resulting in unnecessary power consumption. , It is possible to obtain a low cost, low power consumption rotating magnetic recording / reproducing apparatus. There is an effect that kill.

In the rotary magnetic recording / reproducing apparatus of the present invention, in the above description, the magnetic field saturation means is provided over a timing length at which the magnetic head is to be switched. There is an effect that the operation can be performed with a simple configuration by a single magnetic field saturation unit.

In the rotary magnetic recording / reproducing apparatus of the present invention, since the active state of the opposed magnetic head is reproduction, recording, or erasing, the magnetic characteristics can be maintained without deteriorating the characteristics in any operation. There is an effect that a head switching operation can be performed.

Further, in the rotating magnetic recording / reproducing method of the present invention, at least a pair of magnetic heads are connected in series,
The at least one pair of magnetic heads is disposed on a rotating drum so as to face each other, and a tape is wound at a predetermined angle, and one of the pair of magnetic heads extends over a predetermined angle around a side of the rotating drum other than the side on which the tape is wound. Alternatively, the other side is given a magnetic field that saturates, and the active state of the opposed magnetic head is alternately switched.By switching the opposed magnetic head, the number of channel processes of the subsequent rotary transformer can be halved,
Since the number of channel processes is halved, recording, reproduction and erasing processes can be halved. Further, since switching is not performed in the rotating drum, there is no need to supply power for the switching process, and a circuit switch This eliminates the need for processing and eliminates unnecessary power consumption, thereby achieving low power consumption at low cost.

Further, in the rotary magnetic recording / reproducing method of the present invention, since the above-described saturation magnetic field is applied over the timing length at which the switching of the magnetic head is desired, the switching of a plurality of opposed magnetic heads can be performed. There is an effect that simple processing can be performed by only a single processing that saturates the magnetic field.

In the rotary magnetic recording / reproducing method of the present invention, the active state of the opposed magnetic head is reproduction, recording or erasing. There is an effect that a head switching operation can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing an operation of a permanent magnet according to an embodiment of the present invention.

2A and 2B are diagrams illustrating a head switching state according to the embodiment of the present invention, wherein FIG. 2A is a position a, and FIG. 2B is a position b (a position a);
180-degree rotation position).

FIG. 3 is a diagram showing a head switching operation at the time of reproduction according to the embodiment of the present invention.
In FIG. 3B, the head is in the reproducing state, and in FIG. 3B, the A head is in the reproducing state and the B head is in the saturated state.

FIG. 4 is a diagram for measuring characteristics of a head during reproduction according to the embodiment of the present invention.

FIG. 5 shows the S / N of the head during reproduction according to the embodiment of the present invention.
It is a figure which shows a characteristic and F characteristic.

FIG. 6 is a diagram illustrating a switching state of a plurality of opposed heads according to the embodiment of the present invention.

FIG. 7 is a diagram illustrating switching timing of a plurality of opposing heads according to the embodiment of the present invention.

FIG. 8 is a diagram showing a conventional photo MOS head switch during recording and erasing.

[Explanation of symbols]

1 ... permanent magnet, 2 ... head, 3 ... impedance analyzer, 10 ... drum, 11 ... A head, 1
2 ... B head, 13 ... Rotary transformer, 10 '
...... Drum, 11 '... A head, 12' ... B head, 13 '... Rotary transformer, 14 ... Permanent magnet, 15 ... Tape, 20 ... B head, 21 ... Inductance, 22 ... Reproduction amplifier, 23 ... terminal, 24
... tape, 25 ... A head, 26 ... inductance, 30 ... signal generator, 31 ... resistor, 32 ... A
Head 33, impedance Z, 34 reproduction amplifier, 35 spectrum analyzer, 40 frequency characteristic (F characteristic), 41 S / N characteristic, 50 drum 51 51 A head 52 ... B head, 53 ... C
Head 54, A 'head 55, B' head 5,
6 C head, 57 permanent magnet, 58 tape

Claims (6)

[Claims] At least one pair of magnetic heads connected in series and the at least one pair of magnetic heads are arranged to face each other,
A rotating drum around which the tape is wound at a predetermined angle; and a magnetic field saturation means disposed around the rotating drum other than the side on which the tape is wound over a predetermined angle to apply a magnetic field that saturates one or the other of the pair of magnetic heads. Wherein the active state of the opposed magnetic head is alternately switched. 2. The rotating magnetic recording / reproducing apparatus according to claim 1, wherein said magnetic field saturation means is provided over a timing length at which said magnetic head is to be switched. 3. The rotating magnetic recording / reproducing apparatus according to claim 1, wherein the active state of the opposed magnetic head is reproduction, recording, or erasing. 4. At least a pair of magnetic heads are connected in series, the at least one pair of magnetic heads are arranged oppositely on a rotating drum, a tape is wound at a predetermined angle, and the tape of the rotating drum is wound. A rotating magnetic recording / reproducing method, characterized in that a magnetic field at which one or the other of the pair of magnetic heads saturates is applied over a predetermined angle around the periphery other than the side, and the active state of the opposing magnetic heads is alternately switched. . 5. The rotating magnetic recording / reproducing method according to claim 4, wherein the saturation magnetic field is applied over a timing length for switching the magnetic head. 6. The rotating magnetic recording / reproducing method according to claim 4, wherein the active state of the opposed magnetic head is reproduction, recording or erasing.