Method and apparatus for recording and reproducing a digital signal on a record medium using a rotary head

In a system for recording and reproducing digital signals on a magnetic tape using a rotary head, in which the signals are recorded as a series of slanted tracks without guard bands, pilot signals that control tracking alignment of a playback head are recorded at particular positions in a specific pilot signal record region, independent of the information signal record region. Position detecting signals having various recording lengths are also recorded in the pilot signal region in such a manner that the start position of each position detecting signal corresponds substantially to the center portion of the pilot signal on an adjacent track. When the recorded tracks are reproduced by a rotary playback head having a tracing width greater than the track width, the pilot signals from the two tracks adjacent to the reproduced track on either side thereof are sampled by sampling pulses generated in response to the reproduced position detecting signal and compared in level, and the comparison output is used to control the tracking alignment of the rotary playback head.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates generally to a method and apparatus for recording a 
digital information signal and, more particularly, relates to a method and 
apparatus for recording a digital information signal, a pilot signal and 
an erase signal using a rotary head and employing the pilot signal to 
control tracking alignment of the rotary head during playback. 
2. Description of the Prior Art 
When a video signal and an audio signal are recorded on a magnetic tape 
using a helical-scan rotary head to form one slanted track at every unit 
time and then they are reproduced, it is known that the video signal and 
audio signal are recorded and reproduced in pulse-code modulated (PCM) 
form. The reason is that if the signals are pulse-code modulated, the 
recording and reproducing thereof can be made with high quality. 
In this case, tracking control for controlling the rotary head to 
accurately trace the recorded tracks upon playback is typically carried 
out by using a control signal that has been recorded along one edge of the 
magnetic tape in its width direction by a fixed head. Then, this control 
signal is reproduced by the above fixed head during the reproduction mode 
and the reproduced control signal and the rotary phase of the rotary head 
are maintained in constant phase relation. 
This known tracking control method requires the use of a special fixed 
magnetic head and such fixed magnetic head has a disadvantage in compact 
equipment, because it requires its own mounting space in the recording and 
reproducing apparatus. 
One approach to overcoming the use of the fixed head is a proposed tracking 
control method that does not use such fixed magnetic head but uses only 
the reproduced output signal from the rotary magnetic head to carry out 
the tracking control for the rotary head. This tracking control method is 
disclosed in, for example, U.S. patent application Ser. No. 06/584313 
filed Feb. 28, 1984, now U.S. Pat. No. 4,651,239, and assigned to the 
assignee hereof. This tracking control method relies upon the fact that it 
is easy to time-compress and time-expand the PCM signal and hence that it 
is not necessary to record and reproduce the PCM signal continuously in 
time, unlike an analog signal. Hence, the PCM signal and another different 
signal can easily be recorded on separate regions of each of the plurality 
of slanted tracks formed during recording. 
When the PCM signal is time-compressed and magnetically recorded on a 
record medium by a plurality of rotary heads to form the slanted tracks 
with no guard bands between adjacent tracks, a plurality of tracking 
control pilot signals are recorded in the longitudinal direction in each 
track to form a record region independent of the record region for the PCM 
signal. Upon playback, the recorded track is traced by the rotary head 
having a tracing width greater than the track width, and the tracking of 
the rotary head is controlled by the pilot signals reproduced from the 
tracks adjacent the track being traced by the rotary head. 
As a reference signal for recording and reproducing the tracking control 
pilot signal, a pulse signal (PG) having a frequency of 30 Hz is used that 
is indicative of the rotary phase of the head and that is generated in 
synchronism with the rotation of the motor that drives the rotary head. 
Nevertheless, during playback when the pulse signal PG is used as a 
position detecting reference when the tracking pilot signal is reproduced, 
the reference position of the pulse signal PG can be altered or displaced 
due to mechanical and electrical variations in the parameters of the 
apparatus, caused by changes in temperature and the environment, and such 
variations appear as a kind of tracking error constant (offset) upon 
playback. 
As a result, upon playback, it becomes difficult to reproduce the tracking 
pilot signal with the same timing as that which was present during 
recording, and control of the rotary head becomes imprecise. This provokes 
a particular disadvantage because it becomes impossible to achieve 
compatibility among individual units of the same kind of apparatus. 
Furthermore, because the sampling pulse that is used to reproduce the 
tracking pilot signal over one rotational period of the rotary head is 
formed with the pulse signal PG as a reference, the amount of error 
present therein becomes integrated, so as to be increased by so-called 
jitter and the position of the sampling pulse is displaced in time. 
To remove such shortcoming, a method and apparatus are disclosed in U.S. 
patent application Ser. No. 06/693,270 filed on Jan. 22, 1985, now U.S. 
Pat. No. 4,656,539, in which an erase signal is recorded at the position 
corresponding to the center of adjacent tracking pilot signals, upon 
playback, a sampling pulse is generated in response to this erase signal, 
the tracking pilot signals reproduced from the adjacent track is sampled 
by the sampling pulses generated and the level thereof is compared and a 
tracking signal for a rotary head is generated on the basis of a compared 
output. 
OBJECTS AND SUMMARY OF THE INVENTION 
It is an object of the present invention to provide an improved method and 
apparatus for recording a digital information signal employing a tracking 
control system. 
It is another object of the present invention to provide an improved method 
and apparatus for recording a digital information signal employing a 
tracking control system using a pilot signal and an erase signal recorded 
at predetermined locations on the tracks. 
According to one aspect of the present invention, there is provided a 
method of recording digital signals on a record medium using a rotary head 
that periodically traces the record medium, the method comprising the 
steps of: 
recording a digital information signal at first predetermined areas in a 
plurality of slanted tracks formed on said record medium by said rotary 
head and forming said slanted tracks by said rotary head with no guard 
band between adjacent tracks; 
determining second predetermined areas proximate the end of said slanted 
tracks and differing from said first predetermined areas; 
recording a tracking pilot signal in said second predetermined areas on 
said slanted tracks, whereby said tracking pilot signal is available for 
controlling tracking alignment of a playback head during reproduction of 
said information signal; 
determining predetermined positions in said second predetermined areas 
corresponding substantially to a center portion of said pilot signal on an 
adjacent track; and 
recording a position detecting signal having various recording lengths at 
said predetermined position in said second predetermined areas. 
These and other objects, features and advantages of the present invention 
will become apparent from the following detailed description of the 
preferred embodiment taken in conjunction with the accompanying drawings, 
throughout which like reference numerals designate like elements and parts 
.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Now, an embodiment of a method and apparatus for recording a digital 
information signal according to the present invention will hereinafter be 
described in detail with reference to FIGS. 1 to 8. 
FIG. 1 schematically shows a circuit arrangement of an embodiment of the 
present invention in which only the circuit constructions, that are 
directly concerned with the present invention and that record and 
reproduce a tracking pilot signal, a position detecting signal and an 
erase signal, are shown. In this embodiment of the present invention, the 
tracking pilot signal and the erase signal are recorded and reproduced in 
the normal playback mode, as well as in a variable tape speed playback 
mode, such as when the tape speed is two or three times the normal tape 
speed. Thus, the circuit arrangement for recording and reproducing the 
information signal, such as a PCM signal, for example, is omitted, because 
they form no part of the present invention. 
Referring to FIG. 1, rotary heads 1A and 1B are arranged in contact with a 
magnetic tape 2, which is used as the recording medium, and the rotary 
heads 1A and 1B are mounted on the periphery of a tape guide drum 3 and 
separated by an equal angular distance, namely, 180.degree., as shown in 
FIG. 2. In this embodiment, the magnetic tape 2 is wrapped around the 
outside of tape guide drum 3 at its peripheral portion with an angular 
spacing less than 180.degree., for example, an angular spacing of 
90.degree.. Rotary heads 1A and 1B are rotated at 30 revolutions per 
second in the direction shown by an arrow 4H, and the tape 2 is driven in 
the direction shown by an arrow 4T at a predetermined speed, so that 
slanted magnetic tracks 5A and 5B are respectively formed on the magnetic 
tape 2 one by one by the rotary heads 1A and 1B in a so-called overlapped 
writing state, as shown in FIG. 3. That is, the width (tracing width) W of 
the head gap is selected to be greater than the track width. In this case, 
the width directions of the gaps of the rotary heads 1A and 1B are made 
different from each other relative to the direction perpendicular to their 
tracing direction. In other words, the so-called azimuth angles of the 
rotary heads 1A and 1B are selected to be different from each other to 
take advantage of the azimuth effect to cancel cross-talk. 
It then follows that there occurs a period in which neither of the two 
rotary heads 1A and 1B is in contact with the magnetic tape 2, and this 
period corresponds to the angular range of 90.degree. in this embodiment. 
If this non-contact period is used to perform the addition of redundant 
data during recording and to perform error correction and the like during 
playback, it is possible to simplify the system. 
Referring back to FIG. 1, a pilot signal oscillator or generator 6 produces 
a tracking pilot signal P, which has a frequency f.sub.0 selected to be, 
for example, about 200 KHz and is recorded at a relatively high level. If 
the linearity between tracking phase displacement and a reproduced pilot 
signal output is ensured, the frequency f.sub.0 of the tracking pilot 
signal P is desired to be a frequency presenting a relatively small amount 
of azimuth loss. 
Position detecting signal generators 7 and 8 produce position detecting 
signals S and T that will detect the position of the pilot signal P. These 
position detecting signals S and T are also used as an erase signal for 
the pilot signal P. The reason is that when a new information is recorded 
on a magnetic tape on which the information was previously recorded while 
erasing the previously recorded information, it is not ascertained that 
the new record track is identical in location with the previous 
corresponding record track so that previously recorded pilot signal must 
be erased. The frequencies f.sub.1 and f.sub.2 of the position detecting 
signals S and T are selected to be substantially different from the 
frequency f.sub.0 of the pilot signal P, for example, around 700 kHz and 
500 kHz, respectively. Also the recording levels thereof are selected to 
be such as to substantially erase the pilot signal P. 
Reference numeral 9 designates an oscillator or generator that generates an 
erase signal E.sub.0. In this case, it is preferable that the erase signal 
E.sub.0 is high in erase ratio to erase the signals P, S and T when the 
pilot signal P and the position detecting signals S and T are written in 
an overlapped writing state. The frequency f.sub.3 of the erase signal 
E.sub.0 is selected to be around 2 MHz. 
Recording waveform generators 10, 11, 12 and 13 respond to an edge portion, 
for example, a trailing edge of a delay signal, associated with a pulse 
PG, which will be described in detai1 in the following, and produce 
signals as follows. The recording waveform generator 10, on the basis of 
the pilot signal P from the pilot signal generator 6, produces the pilot 
signals which are arranged with a predetermined time interval tp (tp 
represents the recording time interval of the pilot signal and so on) in 
accordance with the number of the pilot signals P to be recorded per track 
and the arranging manner thereof in the track with a predetermined 
interval. The recording waveform generators 11, 12 and 13, on the basis of 
the position detecting signals S and T and the erase signal E.sub.0 from 
the generators 7, 8 and 9, produce the position detecting signals and the 
erase signal each of which is arranged with a predetermined time interval 
in accordance with the number of the position detecting signals and the 
erase signal recorded per track and the arranging manner thereof in the 
track with a predetermined interval. An OR gate circuit 14 is provided to 
process logically the outputs from the generators 10 to 13. 
A switching circuit 15 is provided to change over the rotary heads 1A and 
1B and changed in position by a switching signal S.sub.1 (FIG. 4A) derived 
from a timing signal generator 16. The timing signal generator 16 is 
supplied with a pulse PG with a frequency of 30 Hz, which is indicative of 
the rotary phase of the rotary heads 1A and 1B, from a pulse generator 17 
in synchronism with the rotation of a motor 18 that drives the rotary 
heads 1A and 1B. The pulse signal with a frequency of 30 Hz from the 
timing signal generator 16 derived from the pulse signal PG, is supplied 
to a phase servo circuit 19 that produces a serv output by which the 
rotary phase of the motor 18 is controlled. 
The pilot signal and the like from the switching circuit 15 which is 
changed in position by the switching signal S.sub.1 from the timing signal 
generator 16 are amplified by an amplifier 19A or 19B and then supplied 
through a contact R of a switching circuit 20A or 20B to the rotary head 
1A or 1B thereby recorded on the magnetic tape 2. The switching circuits 
20A and 20B are connected to the contact R upon recording, whereas they 
are connected to the contact P upon playback. 
An output signal S.sub.2 (FIG. 4D) from the timing signal generator 16 is 
supplied to a delay circuit 21 in which it is delayed with a delay time 
corresponding to the interval between the rotary heads 1A, 1B and the 
mounting position of the pulse generator 17, and the like. A delayed 
output signal S.sub.3 (FIG. 4E) from the delay circuit 21 is fed to each 
of recording timing generators 22 to 25. The switching signal S.sub.1 from 
the timing signal generator 16 is frequency-divided to 1/2 by a frequency 
divider 21' to become a signal S.sub.4 (FIG. 4C) which then is fed to the 
timing generators 23 to 25. The recording timing generators 22 to 25 
generate timing signals which are used as recording references for pilot 
signal and the like. In this case, the trailing edge of the signal S.sub.3 
(FIG. 4E) delayed by the delay circuit 21 is made coincident with the time 
at which the first rotary head comes in contact with the tape during one 
rotation period. 
The recording timing generator 22 produces a signal S.sub.5 (FIG. 4F) which 
is synchronized with the trailing edge of the signal S.sub.3 during the 
half rotation period of one head, for example, the half rotation period of 
the head 1B and which is delayed by time T+3/2tp (T represents the time 
corresponding to the half rotation period of the head) from the trailing 
edge of the signal S.sub.3 during the half rotation period of the other 
head with a predetermined interval T.sub.1 and whose duration time is tp. 
The recording timing generator 23 generates a signal S.sub.6 (FIG. 4G) 
delayed by time 3/2tp from the trailing edge of the signal S.sub.6 during 
only the half rotation period of one head, for example, during only the 
half rotation period of the head 1B with a predetermined interval T.sub.1 
: where during, for example, the odd rotation period of the head, the 
duration time of the signal S.sub.6 is 1/2tp, while during the even 
rotation period of the head, the duration time thereof is 1/4tp. The 
recording timing generator 24 generates a signal S.sub.7 (FIG. 4H) delayed 
from the trailing edge of the signal S.sub.3 by time T during only the 
half rotation period of the other head, for example, only the half 
rotation period of the head 1A with a predetermined interval T.sub.1 where 
the duration time is 1/2tp during the odd rotation period of the head, 
while the druation time is 1/4tp during the even rotation period of the 
head. The recording timing generator 25 generates the following signal 
S.sub.8. That is, in the odd rotation period of the head and during the 
half rotation period of one head, there are generated a pair of pulses 
which are delayed by time tp from the trailing edge of the signal S.sub.3 
with an interval of time 1/2tp therebetween and at a predetermineed 
interval T.sub.1 and each of which pulses has the duration time of 1/2tp, 
while during the other half rotation period of the head, there is 
generated a signal having a duration time tp and delayed by time T+1/2tp 
from the trailing edge of the signal S.sub.3 at a predetermined interval 
T.sub.1. On the other hand, in the even rotation period of the head and 
during the half rotation period of one head, there are generated a pair of 
pulses delayed by a time 1/2tp from the trailing edge of the signal 
S.sub.3 whose duration times are respectively 1/2tp and 3/4tp with an 
interval of 1/4tp at a predetermined interval T.sub.1, while during the 
half rotation period of the other head, there is generated a signal 
delayed by a time T+1/4tp from the trailing edge of the signal S.sub.3 and 
whose duration time is 5/4tp at a predetermined interval T.sub.1 (refer to 
FIG. 4I). 
The signal S.sub.5 (FIG. 4F), the signal S.sub.6 (FIG. 4G), the signal 
S.sub.7 (FIG. 4H) and the signal S.sub.8 (FIG. 4I) from the recording 
timing generators 22, 23, 24 and 25 are respectively supplied to the 
recording waveform generators 10, 11, 12 and 13 substantially as their 
gate signals so that the pilot signal P, the position detecting signals S 
and T and the erase signal E.sub.0 from the generators 6, 7, 8 and 9 are 
respectively supplied through the recording waveform generators 10, 11, 12 
and 13 to the OR gate circuit 14 as shown in FIG. 1. Thus, they are 
developed at the output side thereof as a composite signal S.sub.9 (FIG. 
4J). 
In FIG. 1, amplifiers 26A and 26B are respectively supplied with the 
playback outputs from the corresponding rotary heads 1A and 1B when the 
switching circuits 20A and 20B are changed in position to their contacts P 
upon playback. The respective outputs of these amplifiers 26A and 26B are 
supplied to a switching circuit 27. The switching circuit 27 is 
alternately changed in position by a switching signal S.sub.1 ' (FIG. 5A) 
of 30 Hz from the timing signal generator 16 during the half rotation 
period including the tape contact period of the head 1A and during the 
half rotation period including the tape contact period of the head 1B 
similarly to the recording mode, respectively. 
A band pass filter 28 of a narrow band having a center pass frequency 
f.sub.0 is provided to derive only the pilot signal P from the reproduced 
output of the switching circuit 27. An envelope detector 29 is provided to 
envelope-detect the output from the band pass filter 28 and the output 
from the envelope detector 29 is sampled and then held by a 
sample-and-hold circuit 30. A comparator or differential amplifier 31 is 
provided to compare the outputs from the envelope detector 29 and the 
sample-and-hold circuit 30. A sample-and-hold circuit 32 is provided to 
sample and hold the compared error signal from the differential amplifier 
31. These sample-and-hold circuits 30 and 32 function to sample and hold a 
crosstalk component of the pilot signals recorded on both end portions of 
the tracks adjacent to the track being traced upon normal playback mode as 
will be described later. Then, the output from the sample-and-hold circuit 
32 is delivered to an output terminal 33 as a tracking control signal. 
In order to form the sampling pulse and the like for the sample-and-hold 
circuits 30 and 32, band pass filters 34 and 35 of narrow band having 
center pass frequencies f.sub.1 and f.sub.2 are provided at the output 
side of the switching circuit 27 which derive only the position detecting 
signals S and T from the reproduced output. Outputs S.sub.10 (FIG. 5E) and 
S.sub.11 (FIG. 5F) thereof are supplied through a switching circuit 36 to 
a comparator 37 which is served as a waveform shaping circuit. Similarly 
to the switching circuit 27, the switching circuit 36 is changed in 
position by the switching signal S.sub.1 ' of 30 Hz from the timing signal 
generator 16. 
Sampling pulse generators 38 and 39 are provided at the output side of the 
comparator 37. The sampling pulse generator 38 generates a first sampling 
pulse SP.sub.1 (FIG. 5G) in synchronism with the leading edge of the 
output from the comparator 37, whereas the sampling pulse generator 39 
generates a second sampling pulse SP.sub.2 (FIG. 5H) with the delay of a 
predetermined time tp after the first sampling pulse SP.sub.1 was 
produced. These sampling pulses S.sub.P1 and SP.sub.2 are supplied to the 
sample-and-hold circuits 30 and 32, respectively. 
Next, the circuit operation of FIG. 1 will be described with reference to 
the signal waveforms shown in FIGS. 4 to 5. 
Upon recording, in response to the pulse PG indicative of the rotary phases 
of the rotary heads 1A and 1B derived from the pulse generator 17, the 
timing signal generator 16 produces the signal S.sub.2 shown in FIG. 4D. 
This signal S.sub.2 is supplied to and delayed by a predetermined time by 
a delay circuit 21 and so the delay circuit 21 produces at its output side 
the signal S.sub.3 shown in FIG. 4E. This signal S.sub.3 is supplied to 
the recording timing generators 22 to 25 as mentioned above so that the 
recording timing generator 22 produces at its output side the signal 
S.sub.5 shown in FIG. 4F. The switching signal S.sub.1 from the timing 
signal generator 16 is supplied to the frequency divider 21' so that the 
frequency divider 21' produces at its output side the signal S.sub.4 shown 
in FIG. 4C. This signal S.sub.4 is supplied to the recording timing 
generators 23 to 25 whereby in response to the signals S.sub.3 and 
S.sub.4, the recording timing generators 23 to 25 produce at their output 
sides the signals S.sub.6 to S.sub.8 shown in FIGS. 4G to 4I, 
respectively. 
The signals S.sub.5, S.sub.6, S.sub.7 and S.sub.8 are respectively supplied 
to the recording waveform generators 10, 11, 12 and 13. Thus, the 
recording waveform generator 10 passes therethrough in synchronism with 
the signal S.sub.5 supplied thereto the pilot signal P from the oscillator 
or generator 6 at a predetermined interval and for a predetermined time tp 
as shown in FIG. 4F, the recording waveform generator 11 passes 
therethrough in synchronism with the signal S.sub.6 supplied thereto the 
position detecting signal S from the oscillator 7 at a predetermined 
interval and for a predetermined time as shown in FIG. 4G, the recording 
waveform generator 12 passes therethrough in synchronism with the signal 
S.sub.7 supplied thereto the position detecting signal T from the 
oscillator 8 at a predetermined interval and for a predetermined time as 
shown in FIG. 4H, and the recording waveform generator 13 passes 
therethrough in synchronism with the signal S.sub.8 supplied thereto the 
erase signal E.sub.0 from the oscillator 9 at a predetermined interval and 
for a predetermined time as shown in FIG. 4I. 
The output signals from the recording waveform generators 10 to 13 are 
added together by the OR circuit 14 which then produces at its output side 
the signal S.sub.9 shown in FIG. 4J. 
By the way, at this time, let it be considered that for example, the head 
1B records the track 5B.sub.1 in FIG. 3 (in the first half period tB of 
FIG. 4). Then, the first and second pulses of the signal S.sub.5 in FIG. 
4F correspond to the pilot signals P.sub.A1 and P.sub.A2, respectively, 
the first and second pulses of the signal S.sub.6 in FIG. 4G correspond to 
the position detecting signals S.sub.A1 and S.sub.A2, respectively, and 
the first and second pulses formed of a pair of pulses of the signal 
S.sub.8 in FIG. 4I correspond to the erase signals E.sub.0 which are 
adjacent to the both sides of the position detecting signals S.sub.A1 and 
S.sub.A2, respectively. Accordingly, signals composed of the signals 
corresponding to the alignments of these signals, namely, P.sub.A1, 
E.sub.0, S.sub.A1, E.sub.0 and P.sub.A2, E.sub.0, S.sub.A2 and E.sub.0 are 
produced at each group at the output side of the OR circuit 14. 
Let it be considered that for example, the head 1A records the track 
5A.sub.2 in FIG. 3 (in the first half period tA of FIG. 4). Then, the 
first and second pulses of the signal S.sub.5 in FIG. 4F respectively 
correspond to the pilot signals P.sub.B3 and P.sub.B4, the first and 
second pulses of the signal S.sub.7 in FIG. 4H respectively correspond to 
the position detecting signals T.sub.B3 and T.sub.B4, and the first and 
second pulses of the signal S.sub.8 in FIG. 4I respectively correspond to 
the erase signals E.sub.0 which are adjacent to the one sides of the 
position detecting signals T.sub.B3 and T.sub.B4. Then, the signals 
composed of tne signals corresponding to the alignments of these signals, 
namely, T.sub.B3, E.sub.0, P.sub.B3 and P.sub.B4, E.sub.0 and P.sub.B4 are 
produced at each group at the output side of the OR circuit 14. 
Further, let it be considered that for example, the head 1B records the 
track 5B.sub.2 in FIG. 3 (the second half period tB of FIG. 4). The first 
and second pulses of the signal S.sub.5 in FIG. 4F respectively correspond 
to the pilot signals P.sub.A3 and P.sub.A4, the first and second pulses of 
the signal S.sub.6 in FIG. 4G respectively correspond to the position 
detecting signals S.sub.A3 and S.sub.4A, and the first and second pulse 
formed of a pair of pulses of the signal S.sub.8 in FIG. 4I respectively 
correspond to the erase signals E.sub.0 which are adjacent to the both 
sides of the position detecting signals S.sub.A3 and S.sub.A4. The signals 
composed of the signals corresponding to the alignment of these signals, 
namely, P.sub.A3, E.sub.0, S.sub.A3 and E.sub.0 and P.sub.A4, E.sub.0, 
S.sub.A4 and E.sub.0 are produced at each group at the output side of the 
OR circuit 14. 
Furthermore, let it be considered that for example, the head 1A records the 
track 5A.sub.3 in FIG. 3 (the second half period tA of FIG. 4). Then, the 
first and second pulses of the signal S.sub.5 in FIG. 4F correspond to the 
pilot signals P.sub.B5 and P.sub.B6, respectively, the first and second 
pulses of the signal S.sub.7 in FIG. 4H respectively correspond to the 
position detecting signals T.sub.B5 and T.sub.B6, and the first and second 
pulses of the signal S.sub.8 in FIG. 4I respectively correspond to the 
erase signals E.sub.0 which are adjacent to the one sides of the position 
detecting signals T.sub.B5 and T.sub.B6. The signals composed of the 
signals corresponding to the alignments of these signals, namely, 
T.sub.B5, E.sub.0 and P.sub.B5 and T.sub.B6, E.sub.0 and P.sub.B6 are 
produced at each group at the output side of the OR circuit 14. 
On the other hand, from the timing signal generator 16, there is produced 
the switching signal S.sub.1 as shown in FIG. 4A in response to the pulse 
PG from the pulse generator 17. This signal S.sub.1 is in synchronism with 
the rotation of the rotary heads 1A and 1B so that as shown in FIGS. 4A 
and 4B, during the half rotation period tA of the head in which the signal 
S.sub.1 is at high level, the head 1A comes in contact with the tape 2, 
while during the half rotation period tB in which the signal S.sub.1 is at 
low level, the head 1B comes in contact with the tape 2. Then, the 
switching circuit 15 is changed in position by the switching signal 
S.sub.1 to the state shown in FIG. 1 during the period tA, while it is 
changed in position to the state opposite to that shown in the figure 
during the period tB, thus the head being changed over. 
Accordingly, when the switching circuit 15 is in the position opposite to 
that shown in FIG. 1, the signal S.sub.9 obtained at the output side of 
the OR circuit 14 is supplied through the amplifier 19B and the contact R 
of the switching circuit 20B to the head 1B, whereby at the beginning and 
the end of the contact period of the head 1B with the tape 2 within the 
period tB and in record regions A.sub.T1 and A.sub.T2 for the tracking 
signal provided at both end portions of the track 5B in its longitudinal 
direction distant from the center position of the track 5B in its 
longitudinal direction by an equal length l, the signal S.sub.9 is 
recorded in the odd rotation period of the head (the first half period tB 
of FIG. 4) for a time, tp+1/2tp+1/2tp+1/2tp and a time 
tp+1/2tp+1/2tp+1/2tp, while it is recorded thereon in the even rotation 
period of head (the second half period tB of FIG. 4), for a time 
tp+1/2tp+1/4tp+3/4tp and a time tp+1/2tp+1/4tp+3/4tp, respectively. 
On the other hand, when the switching circuit 15 is in the state as shown 
in FIG. 1, the signal S.sub.9 is supplied through the amplifier 19A and 
the contact R of the switching circuit 20A to the head 1A, whereby at the 
beginning end and the end of the contact period of the head 1A with the 
tape 2 within the period tA and in the similar regions A.sub.T1 and 
A.sub.T2 provided in the both end portions of the track 5A in its 
longitudinal direction distant from the central position of the track 5A 
in its longitudinal direction by the equal distance l, the signal S.sub.9 
is recorded in the odd rotation period (the first half period tA of FIG. 
4) of the head for a time 1/2tp+tp+tp and a time 1/2tp+tp+tp, while it is 
recorded in the even rotation period (the second half period tA of FIG. 4) 
of the head, for a time 1/4tp+5/4tp+tp and a time 1/4tp+5/4tp+tp, 
respectively. 
In other times than those within which these pilot signals, the position 
detecting signals and the erase signals are recorded, though not shown, an 
audio PCM signal of one segment portion to be recorded as one track is 
supplied through the amplifier 19A to the head 1A during the period tA, 
while it is supplied through the amplifier 19B to the head 1B during the 
period tB so that they are recorded on the record region Ap.sub.1 other 
than the record regions of the above-described pilot signals of the 
respective tracks 5A and 5B. 
The reproduction of the signals recorded as mentioned above will be 
described hereinafter. 
Also in this playback mode, the motor 18 is applied with the phase servo 
from the phase servo circuit 19 similarly to the recording mode. 
The signals reproduced from the tape 2 by the rotary heads 1A and 1B are 
respectively supplied through the contact P of the switching circuit 20A 
and the amplifier 26A and the contact P of the switching circuit 20B and 
the amplifier 26B to the switching circuit 27. This switching circuit 27 
is alternately changed over by the switching signal S.sub.1 ' of 30 Hz as 
shown in FIG. 5A from the timing signal generating circuit 16 at the half 
rotation period tA including the tape contact period of the head 1A and at 
the half rotation period tB including the tape contact period of the head 
1B similarly to the recording mode. Accordingly, from this switching 
circuit 27 there is derived an intermittent PCM signal S.sub.R of one 
segment each as shown in FIG. 5C. Then, though not shown this PCM signal 
S.sub.R is supplied to a playback processor to thereby be demodulated to 
the original PCM signal and then further fed to a decoder in which a data 
of each block is detected by the block synchronizing signal, corrected for 
error and de-interleaved and 
then recoverted to the analog audio signal by the D/A converter and then 
fed to the output side. 
The tracking control will be carried out as follows. 
If, now, the head 1B traces the range of a tracing width W including the 
track 5B.sub.1 as shown by one-dot chain lines in FIG. 3, the head 1B 
traces also the tracks 5A.sub.2 and 5A.sub.1 which are adjacent to this 
track 5B.sub.1 so that as shown in FIG. 3, in the region A.sub.T1, the 
pilot signal P.sub.A1 of the track 5B.sub.1, the pilot signal P.sub.B3 of 
the adjacent track 5A.sub.2 and the pilot signal P.sub.B1 of the adjacent 
track 5A.sub.1 are reproduced by the head 1B, while in the region 
A.sub.T2, the pilot signal P.sub.A2 of the track 5B.sub.1, the pilot 
signal P.sub.B4 of the track 5A.sub.2 and the pilot signal P.sub.B2 of the 
adjacent track 5A.sub.1 are reproduced by the head 1B, respectively. At 
this time, the reproduced output of the head 1B derived from the switching 
circuit 27 is supplied to the band-pass filter 28 of the narrow pass band 
having the pass center frequency f.sub.0 which then passes therethrough 
only the pilot signals as its output S.sub.F as shown in FIG. 5D and this 
output signal S.sub.F is fed to the envelope detector 29. 
The output S.sub.R of the switching circuit 27 is also supplied to the 
band-pass filters 34 and 35 of the narrow pass bands having pass center 
frequencies f.sub.1 and f.sub.2 which then pass therethrough at their 
output sides the position detecting signals S.sub.10 and S.sub.11 as shown 
in FIGS. 5E and 5F, respectively. These signals S.sub.10 and S.sub.11 are 
respectively supplied to the switching circuit 36 from which the signal 
S.sub.10 is derived when the switching signal S.sub.1 ' is at low level 
and the signal S.sub.11 when it is at high level which then are fed to the 
comparator 37. 
The comparator 37 compares the signals S.sub.10 and S.sub.11 supplied 
thereto with a reference value, waveform-shapes them and supplies the same 
to the sampling pulse generators 38 and 39. The sampling pulse generator 
38 produces the first sampling pulse S.sub.P1 in synchronism with the 
rising-up edge of the wave-form-shaped signal S.sub.10 as shown in FIG. 5G 
and this first sampling pulse S.sub.P1 is supplied to the sample-and-hold 
circuit 30. At this time, as will be clear from FIG. 5, the sampling pulse 
S.sub.P1 makes the sample-and-hold circuit 30 sample the crosstalk 
components of the pilot signals P.sub.B4 and P.sub.B4 of the adjacent 
track 5A.sub.2 at the side opposite to the transportation direction of the 
tape 2 shown by an arrow 4T (FIG. 3) and the signal thus sampled is 
supplied to one input terminal of the differential amplifier 31 as the 
tracking signal of advanced phase. 
After the time tp since the sampling pulse S.sub.P1 was produced, the 
crosstalk component of the pilot signals P.sub.B1 and P.sub.B2 of the 
adjacent track 5A.sub.1 at the side of the tape transport direction is 
supplied to the other input terminals of the differential amplifier 31 
from the envelope detector 29 as the tracking signals of delayed phase, 
respectively. Accordingly, the differential amplifier 31 compares the 
tracking signals corresponding to the crosstalk components of the pilot 
signals P.sub.B3, P.sub.B1, and P.sub.B4, P.sub.B2, in turn. 
Then, the compared error signal from the differential amplifier 31 is 
supplied to the sample-and-hold circuit 32 in which it is sampled by the 
sampling pulse S.sub.P2 produced from the sampling pulse generator 39 
after the time tp since the sampling pulse S.sub.P1 was produced. 
Consequently, from the sample-and-hold circuit 32, the difference between 
the two inputs to the differential amplifier 31 is produced as the 
tracking control signal. This tracking control signal is supplied from the 
output terminal 33 to a capstan motor (not shown) which then controls the 
transported amount of the tape. Thus, the head 1B is controlled so that 
the level difference between the two inputs to the differential amplifier 
31 becomes zero or when the head 1B traces the track 5B.sub.1, the head 1B 
traces the two tracks 5A.sub.2 and 5A.sub.1 at both sides of the track 
5B.sub.1 with the same amount. In other words, the head 1B is controlled 
to trace the track 5B.sub.1 in such a way that the central position of the 
width direction of the gap of the head 1B is made coincident with the 
central position of the track 5B.sub.1. 
As to the other tracks, the heads will be controlled similarly. For 
example, when the head 1A traces the track 5A.sub.2, there are obtained 
the crosstalk components of the pilot signals P.sub.A3, P.sub.A4, and 
P.sub.A1, P.sub.A2 of the adjacent tracks 5B.sub.2 and 5B.sub.1. Thus, the 
crosstalk components of the pilot signals P.sub.A3 and P.sub.A4 are 
sampled by the sampling pulse S.sub.P1 supplied from the sampling pulse 
generator 38 to the sample-and-hold circuit 30 to thereby produce the 
tracking signal. This tracking signal is supplied to the differential 
amplifier 31 at the next stage and the output corresponding to the 
crosstalk components of the pilot signals P.sub.A1 and P.sub.A2 and 
derived from the envelope detector 29 is supplied to the differential 
amplifier 31 in which the tracking signals respectively corresponding to 
the crosstalk components between the pilot signals P.sub.A1 and P.sub.A2 
and P.sub.A4 and P.sub.A2 are compared with one another. The compared 
error signal is sampled by the sampling pulse SP.sub.2 which is supplied 
to the sample-and-hold circuit 32 so as to produce the tracking control 
signal for the head 1A. 
Similarly, when the head 1B traces the track 5B.sub.2, as shown in FIG. 3, 
the crosstalk components of the pilot signals P.sub.B5, P.sub.B6 and 
P.sub.B3, P.sub.B4 of the adjacent tracks 5A.sub.3 and 5A.sub.2 are 
produced. Thus, the crosstalk components of the pilot signals P.sub.B5 and 
P.sub.B6 are sampled by the sampling pulse SP.sub.1, the tracking signals 
corresponding to the crosstalk components of the pilot signals P.sub.B5, 
P.sub.B3 and P.sub.B6, P.sub.B4 are compared with one another by the 
differential amplifier 31. Finally, the compared error signal is sampled 
by the sampling pulse SP.sub.2 to thereby produce the tracking control 
signal for the head 1B. 
Similarly, when the head 1A traces the track 5A.sub.3, as shown in FIG. 3, 
the crosstalk components of the pilot signals P.sub.A5, P.sub.A6 and 
P.sub.A3, P.sub.A4 of both the adjacent tracks 5B.sub.3 and 5B.sub.2 are 
produced. Thus the crosstalk components of the pilot signals P.sub.A5 and 
P.sub.A6 are sampled by the sampling pulse SP.sub.1 and the tracking 
signals corresponding to the crosstalk components of the pilot signals 
P.sub.A5, P.sub.A3 and P.sub.A6, P.sub.A4 are controlled by the 
differential amplifier 31. Finally, the compared error signal is sampled 
by the sampling pulse SP.sub.2 to thereby produce the tracking control 
signal corresponding to the head 1A. 
FIG. 6 shows an example of a practical circuit arrangement of the sampling 
pulse generator 39. In the figure, reference numeral 40 designates a 
counter for counting the pulses of the position detecting signal supplied 
thereto from the comparator 37. Reference numeral 41 designates a data 
selector which is responsive to the signals S.sub.4 and S.sub.1 ' and then 
selects the data (set values) of four kinds which are classified by the 
contents of the position detecting signals, namely, classified by the 
frequencies and the recording lengths of the position detecting signals S 
and T in this embodiment. Reference numeral 42 designates a coincidence 
detecting circuit for detecting whether the count value of the counter 40 
coincides with the data of the data selector 41. As this coincidence 
detecting circuit 42, there is used, for example, a digital comparator. 
Reference numerals 43 to 46 respectively designate delay circuits each of 
which derives a predetermined delay signal from the sampling pulse 
SP.sub.1. The counter 40 is enabled by the output from the delay circuit 
44 and is then cleared by the output from the delay circuit 45. Reference 
numeral 47 designates a D-type flip-flop circuit and to an input terminal 
D of this flip-flop circuit 47, there is supplied the output from the 
coincidence detecting circuit 42. To a clock terminal CK of the flip-flop 
circuit 47, there is substantially applied the sampling pulse SP.sub.1 
through the delay circuit 46 and to a reset terminal R thereof, there is 
supplied the output of the delay circuit 45. 
Reference numeral 48 designates a gate circuit, for example, an AND 
circuit. To one input terminal of this AND circuit 48, there is supplied 
the output of the delay circuit 43, while to the other input terminal 
thereof, there is supplied the output developed at an output terminal Q of 
the flip-flop circuit 47. Then, the sampling pulse SP.sub.2 is produced at 
the output terminal thereof. 
The operation of the sampling pulse generator 39 shown in FIG. 6 will be 
described with reference to the signal waveform diagram of FIG. 7. 
When a signal S.sub.13 as the position detecting signal, shown in FIG. 7D 
is supplied from the comparator 37 to the sampling pulse generator 38, 
this sampling pulse generator 38 produces the sampling pulse SP.sub.2 in 
synchronism with the leading edge of the first pulse of the signal 
S.sub.13 shown in FIG. 7H. This sampling pulse SP.sub.1 is supplied to the 
above-described sample-and-hold circuit 30 (FIG. 1) and also to the delay 
circuits 43 to 46. 
The delay circuit 44 produces at its output side a signal S.sub.12 having a 
duration time corresponding to substantially 1/2tp in synchronism with the 
sampling pulse SP.sub.1 as shown in FIG. 7C. This signal S.sub.12 is 
supplied to the counter 40 as the enable signal thereof. 
The counter 40 counts the pulse length of the signal S.sub.13 from the 
comparator 37 during the period in which the signal S.sub.12 is at high 
level. On the other hand, the data selector 41 responds to the signals 
S.sub.1 ' and S.sub.4 which are respectively shown in FIGS. 7A and 7B and 
selects.th data relating to the position detecting signal. If the selected 
data and the content of the counter 40 coincide with each other, the 
coincidence detecting circuit 42 produces at its output side a signal 
S.sub.14 which continues from the trailing edge of the final pulse of the 
signal S.sub.13 by a predetermined time as shown in FIG. 7E. This signal 
S.sub.14 is supplied to the flip-flop circuit 47 as the data thereof. 
The delay circuit 46 produces a signal S.sub.15 in synchronism with the 
sampling pulse SP.sub.1 with a delay of a predetermined time .DELTA.t1 
therefrom as shown in FIG. 7F. This signal S.sub.15 is supplied to the 
clock terminal CK of the flip-flop circuit 47, in which the signal 
S.sub.14 supplied to the input terminal D thereof is latched. In this 
case, the delay time .DELTA.t1 of the delay circuit 46 is selected to 
satisfy the condition of tp&gt;.DELTA.t1&gt;tp/2. 
The delay circuit 45 produces a signal S.sub.16 in synchronism with the 
sampling pulse SP.sub.12, and delayed with respect thereto by a 
predetermined time .DELTA.t2 as shown in FIG. 7G. This signal S.sub.16 is 
supplied to the counter 40 to thereby clear the content thereof and also 
supplied to the flip-flop circuit 47 to thereby reset the same. As a 
result, at the output side of the flip-flop circuit 47, there is produced 
a signal S.sub.17 as shown in FIG. 7I. In this case, the delay time 
.DELTA.t2 of the delay circuit 45 is selected so as to satisfy the 
condition of .DELTA.t2&gt;tp. 
Further, the delay circuit 43 produces a signal S.sub.18 in synchronism 
with the sampling pulse SP.sub.1 after therefrom by a predetermined time 
tp shown in FIG. 7J. This signal SP.sub.18 is supplied to one input 
terminal of the AND circuit 48. Since the AND circuit 48 is supplied at 
the other input terminal thereof with the signal S.sub.17 which is formed 
as described above, this signal S.sub.17 is supplied to the AND circuit 48 
as its substantially gate signal so as to open the gate thereof so that in 
response to the signal S.sub.18, the sampling pulse SP.sub.2 as shown in 
FIG. 7K is produced. This sampling pulse SP.sub.2 is supplied to the 
sample-and-hold circuit 32. 
In this way, the sampling pulse SP.sub.2 can be produced. 
In this case, the sampling pulse SP.sub.2 can be produced by the data 
processing of a microcomputer (not shown). 
This will be described with reference to the flow chart of FIG. 8. 
Reference to FIG. 8, when the recording apparatus is set in a playback mode 
at step 100, the program goes to step 110 in which the position detecting 
signals S and T are detected. If they are not detected, the detecting 
operation is repeated at step 110 until the position detecting signals S 
and T are detected. If the position detecting signals S and T are detected 
at step 110, the first sampling pulse SP.sub.1 is produced on the basis of 
the position detecting signals S and T at step 120 and the pulse Ni of the 
first sampling pulse SP.sub.1 is counted during only the detection periods 
of the position detecting signals S and T at step 130. 
Then, the program goes to the next step 140 in which it is judged whether 
the detected position detecting signals S and T are those which are 
produced first in the playback mode or not. If they are the first ones, 
the program goes to step 150 in which it is judged whether the interval is 
the interval 1/2tp or not and 1/4tp or not. If the interval satisfies 
either of them, the program goes to step 160 in which the second sampling 
pulse SP.sub.2 is produced. If neither of the 1/2tp interval nor 1/4tp 
interval are satisfied at step 150, they are not the position detecting 
signals S and T so that the program returns to the step 110. 
If at step 140 it is judged that the position detecting signals S and T are 
ones which are produced in the second time after the apparatus was set in 
the playback mode, the program goes to step 170 in which it is judged 
whether the polairy of the signal S.sub.4 is changed or not. If the 
polarity of the signal S.sub.4 is changed, the program goes to step 180 in 
which it is judged whether the preceding detection interval is 1/2tp or 
1/4tp. If it is 1/2tp, the program goes further to step 190 in which it is 
judged whether the interval of the present position detecting signal is 
1/4tp or not. If it is 1/4tp, the position detecting signal is the true 
position detecting signal so that at step 160, the second sampling pulse 
SP.sub.2 is produced. If on the other hand it is not 1/4tp, the program 
returns to step 110. 
If it is judged that the preceding detecting interval is 1/4tp at step 180, 
the program goes to step 200 in which it is judged whether the interval of 
the present position detecting signal is 1/2tp or not. If it is 1/2tp, it 
is the true position detecting signal so that the program returns to step 
160 in which the second sampling pulse SP.sub.2 is produced. If on the 
other hand it is not 1/2tp, the program returns to step 110. 
The operations of the steps 170 to 200 will be described in detail with 
reference to FIGS. 5B, 5E and 5F. At step 170, if it is judged that the 
polarity of the signal S.sub.4 is changed at the central portion of, for 
example, FIG. 5B, the program goes to step 180 in which it is judged 
whether T.sub.B4 of the signal S.sub.11 shown in FIG. 5F is 1/2tp or not 
and 1/4tp or not. Since it is 1/2p, the program goes to step 190. At step 
190, it is judged whether S.sub.A3 of the signal S.sub.10 shown in FIG. 5E 
is 1/4tp or not. Since it is 1/4tp, the program goes to step 160 in which 
the second sampling pulse SP.sub.2 is produced. At step 190, if the signal 
S.sub.A3 is not 1/4tp, the program returns to step 110. 
At step 180, if T.sub.B4 is 1/4tp, it is judged that it is not the T.sub.B4 
of the signal S.sub.11 but the signal T.sub.B6 (accordingly, the time 
point at which the polarity of the signal S.sub.4 is changed is not the 
central portion of FIG. 5B but the right hand end portion thereof), the 
program goes to step 200. At step 200, it is judged whether S.sub.A5 (not 
shown) of the signal S.sub.10 shown in FIG. 5E is 1/2tp or not. Since it 
should be 1/2tp, the second sampling pulse SP.sub.2 is produced at step 
160. If at step 200 it is judged that the signal S.sub.A5 is not 1/2tp, 
the program returns to step 110. 
If at step 170 the polarity of the signal S.sub.4 is not changed, the 
program goes to step 210 at which it is judged whether the detecting 
interval is the same as the preceding position detecting signal or not. If 
it is the same, the program returns to step 160 at which the second 
sampling pulse SP.sub.2 is produced. This will be described with reference 
to FIG. 5E. Since, for example, the first and second pulses S.sub.A1 and 
S.sub.A2 of the position detecting signal S.sub.10 are same as 1/2tp, the 
second sampling pulse SP.sub.2 is produced at step 160. Then, if, at step 
210, it is judged that the detecting intervals thereof are not equal to 
each other, such detection is regarded as the mis-detection and hence the 
first sampling state is maintained and the program returns to step 110. 
As described above, by the signal processing of the microcomputer, it 
becomes possible to produce the second sampling pulse SP.sub.2. 
While in the above embodiment the rotary head assembly is such a special 
one that a tape is wound over an angular range narrower than an angular 
spacing of the heads to thereby carry out the recording and the 
reproducing, it is needless to say that this invention can be applied to a 
rotary head assembly in which the tape is wrapped over an angular range 
same as the angular spacing of the heads in the ordinary way. 
As set forth above, according to this invention, when the recorded track is 
traced by a rotary head, a plurality of position detecting signals which 
are different in frequency between the adjacent tracks and different in 
recording length between the tracks relative to the same frequency are 
recorded on every predetermined track, the beginning end of these position 
detecting signals are taken as a reference so as to form a pulse signal 
which detects the pilot signal, and the tracking control of the rotary 
head is carried out by the tracking control signal based on the detected 
output. Accordingly, even if the apparatus has a mechanical secular 
variation, a temperature change or a jitter, without being affected by 
these parameters, it is possible to carry out the tracking control with 
good precision even when the apparatus for playback mode is different from 
that of the recording mode and also it is possible to present the 
compatibility between the apparatus. 
Further, since the position detecting signals are different in frequency 
between the adjacent tracks, it is free of the influence of the crosstalk 
component and it is possible to widen a range in which the threshold level 
for detecting the position detecting signal is set. 
Furthermore, since the position detecting signals are different in 
recording length between the adjacent tracks, the adjacent tracks can be 
discriminated from each other and it becomes possible to detect the 
position detecting signals in spite of a track displacement of a wide 
range. 
In addition, since the position detecting signal for detecting the position 
of the tracking control pilot signal is recorded so as to have a beginning 
end near the center of the adjacent pilot signals, it becomes unnecessary 
to provide a circuit and the like for delaying the position detecting 
signal so as to place such beginning end near the center of the pilot 
signal, thus the circuit arrangement being simplified by that much. 
The above description is given on a single preferred embodiment of the 
invention but it will be apparent that many modifications and variations 
could be effected by one skilled in the art without departing from the 
spirits or scope of the novel concepts of the invention so that the scope 
of the invention should be determined by the appended claims only.