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BACKGROUND OF THE INVENTION
This invention relates to head switching control apparatus and, more
particularly, to such apparatus which is used in video signal processing
apparatus for selectively connecting individual rotary transducer heads,
one at a time, to video signal receiving circuitry such that transient
noise or pulses which may be produced when the heads are switched, or
connected, are timed to occur at substantially the same time during
successive video fields.
In a typical video signal recorder, such as a magnetic video signal
recorder, two or more rotary magnetic heads scan a recording medium. In
one type of recorder, this medium is magnetic tape and the recording
system is the so-called video tape recorder (VTR). In a typical two-head
VTR, each head scans an oblique track across the magnetic tape. During a
recording operation, each track is provided with a video signal field
derived from the usual interlaced video fields of, for example, a
composite video signal which is about to or has been broadcasted. Thus,
each field recorded in a respective track is comprised of video signal
information, horizontal synchronizing pulses and the vertical blanking
interval. In accordance with a conventional television signal, the
vertical blanking interval is formed of a number of equalizing pulses
followed by a number of vertical synchronizing pulses followed by another
series of equalizing pulses and then a number of horizontal synchronizing
pulses preceding the video signal information. In order to record the
composite video signal properly in each track, the continuous signals
supplied to the VTR must be divided between first one and then the other
rotary head. That is, suitable switching apparatus is provided to supply
the continuous signal to one head while it scans the magnetic tape, and
then to the other head when such other head rotates into contact with the
tape. Similarly, during a reproducing, or playback, operation, a switching
operation between the two heads must be performed so as to recover a
continuous video signal therefrom. That is, when one head scans a track,
the previously recorded video signals which are reproduced thereby must be
coupled to suitable video signal receiving circuitry; and when the other
head rotates into contact with the tape, that head must be switched to the
signal receiving circuitry.
One type of head switching control apparatus which has been proposed by the
prior art exercises control over the head switching circuitry both during
recording and during playback. This proposal recognizes that it is
possible to generate a gap from the time one head is disconnected from the
signal receiving circuitry until the time that the other head is connected
thereto. That is, a gap in the desired continuous video signal may be
produced during this head switching, or change-over, period. The prior art
suggests that this gap can be avoided if one head reaches the end portion
of a track concurrently with the other head reaching the beginning portion
of its track, thereby exhibiting some "overlap" in the respective track
scans. If this overlap is present during recording, the same information
will be recorded by both heads in respective tracks during the overlapping
period. Similarly, during signal reproduction, the signals reproduced by
one head will be the same as the signals reproduced by the other head
during this overlapping period. According to this prior art proposal, if
both heads are connected simultaneously to the signal receiving circuitry
during this overlapping period, there will be no gap in the continuous
video signal which is reproduced. However, at the start of this
overlapping period and at the conclusion thereof, switching circuitry is
actuated to selectively connect and disconnect the respective transducer
heads. Hence, two transient pulses, or noise, will be generated as a
function of this head-connect and head-disconnect switching. Although the
particular times of occurrences of such transient pulses may be
predictable such that clamping or blanking signals can be produced so as
to mute or compensate for such noise, there is the possibility that,
because of tape shrinkage, small differences in mechanical tolerances
among different VTR devices, and the like, the precise times of occurrence
of the transient pulses may deviate from the expected times. Consequently,
transient noise may be provided during a horizontal line interval in the
reproduced continuous video signal, this transient noise appearing as
streaks of light in the ultimately reproduced video picture.
In another prior art proposal, head switching control apparatus is used
only during a reproducing operation and not during signal recording.
Rather, during recording, the composite video signal is applied
simultaneously to both rotary heads. Effective switching between these
heads is performed automatically by reason of the contact of one or the
other of the heads with the magnetic recording medium. That is, the signal
supplied to the head which is not in contact with the medium is, of
course, not recorded. However, since the same signal is applied to the
other head which is in contact with the medium, this signal is recorded in
a respective track on the medium. If the heads are spaced apart by
180.degree. and each head scans a track whose effective length is slightly
greater than 180.degree., then the end portion of one track will have
signals which are the same as those recorded in the beginning portion of
the next adjacent track. Typically, the portion of the composite video
signal which is recorded in this "overlapping" relation is the vertical
blanking interval. During signal playback, a position pulse generator is
provided to detect the position of each head relative to the recording
medium. For example, a pulse is produced when one head first comes into
contact with the medium to scan a track thereacross, and another pulse is
produced when the other head first comes into contact with the medium to
scan another, adjacent track. These pulses control the head switch-over.
That is, when the first head-position pulse is produced, switching
circuitry is actuated to couple the corresponding head to the signal
receiving circuitry; and when the next head-position pulse is produced,
the switching circuitry is actuated to disconnect the first head and to
connect the other head to the receiving circuitry.
In the foregoing prior art proposal, a transient pulse, or noise, is
produced when the switching circuitry is actuated. Ideally, this transient
pulse will be produced at the same time during each vertical blanking
interval (i.e., when the playback heads are switched over). However, in
practice, because of tape shrinkage, different mechanical tolerances in
different VTR systems, slightly different head speeds, and the like, the
time of head switch-over, and thus the time that the transient pulse is
produced, may vary. That is, the transient pulse may occur at the time of
occurrence of an equalizing pulse, or between successive equalizing
pulses, or at any other time during the vertical blanking interval. The
resultant continuous video signal which is reproduced by the VTR system
thus will have a transient pulse which occurs asynchronously at arbitrary
locations. Although this may not be noticeable or detrimental in a home
entertainment system, this arbitrarily occurring transient pulse is not
acceptable for television broadcasting of the reproduced video signal.
OBJECTS OF THE INVENTION
Therefore, it is an object of the present invention to provide improved
head switching control apparatus for use in a video signal processing
system which overcomes the aforenoted problems attending prior art
proposals.
Another object of the present invention is to provide an improved head
switching control apparatus wherein individual ones of plural rotary
transducer heads are connected, one at a time, and without overlap, to
signal receiving circuitry in video signal processing apparatus.
A further object of this invention is to provide improved head switching
control apparatus for use in a video signal processing system wherein a
transient pulse, or noise, which is produced as a result of switching over
from one to another of plural heads is synchronized to occur at the same
relative time during predetermined intervals.
An additional object of this invention is to provide head switching control
apparatus for use in a video signal reproducing system of the type having
a pair of rotary magnetic playback heads wherein the output of one head is
supplied to a demodulator and then the output of the other head is
supplied to the demodulator, switching between these heads being timed to
occur at the same relative time during each vertical blanking interval.
Various other objects, advantages and features of the present invention
will become readily apparent from the ensuing detailed description, and
the novel features will be particularly pointed out in the appended
claims.
SUMMARY OF THE INVENTION
In accordance with the present invention, head switching control apparatus
is provided for use in a video signal processing system of the type having
plural rotary transducer heads for scanning successive tracks across a
recording medium, each track having recorded therein a composite video
signal comprised of video information, horizontal synchronizing signals
and a vertical blanking interval. The head switching control apparatus
functions to selectively connect individual transducer heads, one at a
time, to video signal receiving circuitry. This head switching control
apparatus is comprised of a position pulse generator for generating
position pulses representing the relative positions of the transducer
heads with respect to the recording medium; a bi-state circuit responsive
to successive position pulses for switching between its first and second
states as the transducer heads rotate into predetermined positions with
respect to the recording medium; switching circuitry coupled to the
transducer heads for electrically connecting individual heads to the video
signal receiving circuitry; a synchronizing signal separator coupled to
the video signal receiving circuitry for separating the synchronizing
signals included in the vertical blanking interval from the composite
video signal; and a switch pulse generator coupled to the synchronizing
signal separator and to the bi-state circuit for generating switch pulses
which are synchronized with the separated synchronizing pulses in response
to the change of states of the bi-state circuit, these switch pulses being
applied to actuate the switching circuitry so as to connect the transducer
heads, one at a time, to the video signal receiving circuitry.
BRIEF DESCRIPTION OF THE DRAWINGS
The following detailed description, given by way of example, will best be
understood in conjunction with the accompanying drawings in which:
FIG. 1 is a block diagram of a preferred embodiment of the present
invention; and
FIGS. 2A-2J are waveform diagrams which are useful in understanding the
operation of the block diagram shown in FIG. 1.
DETAILED DESCRIPTION OF A PREFERED EMBODIMENT
Referring now to the drawings, and in particular to FIG. 1, there is
illustrated a block diagram of a preferred embodiment of head switch
control apparatus which can be used in a video recording system. Although
this control apparatus can be used in the performance either of a
recording operation or a reproducing operation, it will be described in
the environment of a signal playback system. Furthermore, while the video
recorder may comprise a VTR, a magnetic sheet recorder, a magnetic card
recorder, or the like, in the interest of simplification, the illustrated
embodiment will be described for use with a VTR. As will become apparent,
the head switch control apparatus can be used with other types of
recording systems, such as an optical recorder/playback device, or the
like. In the further interest of simplification, the video recorder will
be assumed to include two transducer heads; but it should be understood
that, if desired, multiple heads can be used.
In the illustrated embodiment, a pair of transducer heads 12a, 12b, which
may comprise magnetic recording/playback heads, are adapted to be rotated
so as to scan parallel, successive tracks obliquely across the surface of
a recording medium 10, such as magnetic recording tape. In an alternative
embodiment, heads l2a and 12b may be capable of signal playback only. In
either embodiment, these heads are mounted on a suitable support 14 which
is coupled to a rotary shaft 16 driven by a motor 18. This motor is a
servo-controlled motor such that the rotation of shaft 16, and thus heads
12a and 12b, is accurately controlled and is determined partly by the
longitudinal movement of tape 10, as is known to those of ordinary skill
in the video signal recording art. In order to sense the relative position
of heads 12a and 12b with respect to recording medium 10, a magnet 20,
such as a magnet formed of permanent magnetic material, is mounted or
otherwise secured to shaft 16 so as to be rotated with the heads. Magnet
20 is particularly aligned such that it rotates past a predetermined point
when head 12a first comes into contact with the recording medium so as to
commence its scan of an oblique track. The position of magnet 20, and thus
the position of head 12a, is sensed by a pickup coil 22a which is fixedly
disposed at the aforenoted point. Similarly, another pickup coil 22b is
disposed at a second location so as to sense the movement of magnet 20
therepast. This movement of the magnet is sensed when head 12b first comes
into contact with recording medium 10 so as to commence its scan of an
oblique track.
Pickup coils 22a and 22b function as a position pulse generator and are
coupled to pulse amplifiers 24a and 24b, respectively. These amplifiers
function to shape the signals produced by the respective pickup coils so
as to form rectangular pulses of predetermined duration. Pulse amplifiers
24a and 24b are coupled to adjustable delay circuits 26a and 26b,
respectively, these delay circuits functioning to impart a delay to the
respective pulses applied thereto. The purpose of these delay circuits is
explained hereinbelow.
The output of delay circuit 26a is coupled to the set input of a bi-state
device 28, such as a bistable multivibrator, or flip-flop circuit. The
output of delay circuit 26b is coupled to the reset input of this
flip-flop circuit. As is understood by those of ordinary skill in the art,
flip-flop circuit 28 is a bi-state device which is adapted to be set to a
first state in response to a pulse applied to its set input, and to be
reset to a second state in response to a pulse applied to its reset input.
The particular state assumed by flip-flop circuit 28 is represented by a
signal provided at its output. For the purpose of the present discussion,
it will be assumed that a signal of relatively low level, hereinafter
designated a binary 0, is produced at the output of flip-flop circuit 28
to represent that this flip-flop circuit is reset to its second state, and
that this output signal switches to a relatively higher level, hereinafter
designated as a binary 1, when the flip-flop circuit is set to its first
state.
The output of flip-flop circuit 28 is coupled to a synchronizing, or
re-timing circuit 30. This synchronizing circuit is of a type including a
signal information input and a timing signal input. An output signal is
produced thereby which corresponds to the received information signal in
coincidence with a timing pulse applied to the timing input. In one
embodiment thereof, synchronizing circuit 30 is a timing-pulse controlled
flip-flop circuit, such as a D-type flip-flop, wherein the information
signal input is represented as the "D" input and the timing pulse input is
represented as the "T" input. The state of this D-type flip-flop circuit
is determined by the logical sense of the signal applied to its D input,
but in coincidence with the timing pulse which is applied to its T input.
Thus, if a binary 1 is applied to the D input of flip-flop circuit 30, the
output signal produced thereby as a representation of its state will be
switched to a binary 1 when a timing pulse is applied to its T input. This
state will be maintained until the information signal applied to its D
input changes to a binary 0 and another timing pulse is applied to its T
input.
The signal produced by synchronizing circuit 30, that is, the state of this
flip-flop circuit, is used to control switching circuitry that is
connected to respective transducer heads 12a and 12b so as to selectively
couple these heads to further signal receiving circuitry. As will be
explained below, when head 12a contacts recording medium 10 so as to
reproduce the signals which have been recorded in a track, a switching
circuit 44a is actuated to couple the reproduced signals from head 12a to
the signal receiving circuitry. Similarly, when head 12b contacts
recording medium 10 so as to reproduce the signals which have been
recorded in a track, a switching circuit 44b is actuated to couple these
reproduced signals to the signal receiving circuitry. Moreover, switching
circuits 44a and 44b are controlled such that one is opened so as to
disconnect its associated head from the signal receiving circuitry
simultaneously with the closing of the other. To this effect, switching
circuits 44a and 44b may comprise conventional solid-state switching
devices having switch pulse control inputs coupled to the output of
synchronizing circuit 30. In order to simplify the present discussion,
these respective switching circuits are illustrated as mechanical
switching devices.
Transducer 12a is coupled through an amplifier 42a, such as a playback
amplifier, to switch 44a; and transducer 12b similarly is coupled through
a playback amplifier 42b to switch 44b. A balancing circuit 46,
illustrated as a potentiometer, is supplied with the signals produced by
switches 44a and 44b and, after amplitude-balancing these signals,
supplies them to signal receiving circuitry 48. It is appreciated that the
illustrated signal reproducing system is adapted to reproduce video
signals which have been recorded in successive tracks on medium 10.
Typically, these video signals are modulated prior to recording, and the
modulated video signals are recorded. Accordingly, in order to recover the
original video signals, signal receiving circuitry 48 preferably includes
a demodulator which is adapted to demodulate the reproduced, modulated
video signals. In one example, the video signals are recorded as
frequency-modulated signals. Accordingly, demodulator 48 would comprise a
frequency demodulator. The output of demodulator 48 is coupled to a video
signal output 52 and, additionally, to a synchronizing signal separator
circuit 50. This latter circuit is known to those of ordinary skill in the
art and is adapted to separate the various video synchronizing signals
included in the composite video signal derived from demodulator 48. These
synchronizing signals, which include the horizontal synchronizing pulses
and the various synchronizing signals included in the vertical blanking
interval, are applied to the timing pulse input of synchronizing circuit
30.
The operation of the head switch control apparatus illustrated in FIG. 1
now will be described with reference to FIGS. 2A-2J. The video signals
which are recorded on recording medium 10 are composite video signals
containing video information, horizontal synchronizing signals and various
other synchronizing signals included in the vertical blanking interval.
The video information may be color television signal information, such as
an NTSC color video signal. Typically, the vertical blanking interval
separates successive fields of signal information and is provided with a
plurality of equalizing pulses followed by a plurality of vertical
synchronizing pulses followed by another set of equalizing pulses and then
a plurality of horizontal line intervals from which video signal
information is omitted. As mentioned above, a field of video signals is
recorded in each track on medium 10. If desired, such tracks may be
recorded either by heads 12a and 12b, which will be constructed as
record/playback heads, or by other video signal recording apparatus.
Furthermore, in the intended application for use in television signal
broadcasting, the composite video signals are recorded as modulated
signals, such as frequency-modulated video signals, in the respective
tracks. Furthermore, the signal recording format preferably is such that
the vertical blanking interval is recorded in the beginning portion of a
track, followed by the field of video information, and the next vertical
blanking interval is recorded in the end portion of that track. Also, the
recording heads generally are disposed such that one head reaches the end
portion of a track just as the other head first contacts the recording
medium, thereby resulting in an overlap of signals recorded on adjacent
tracks. That is, the vertical blanking interval recorded in the end
portion of one track is the same as the vertical blanking interval
recorded in the beginning portion of the next adjacent track.
In a signal reproducing operation, let it be assumed that head 12a is
rotated into position to reproduce the video signals recorded in a track
just as head 12b departs from a track. Hence, the video signals reproduced
by head 12a appear as shown in FIG. 2B. Slope 62 shown in FIG. 2B
represents the movement of head 12a into contact with recording medium 10.
At the same time, the signals reproduced by head 12b appear as shown in
FIG. 2A. Slope 64, which is shown in FIG. 2A, represents the departure of
head 12b from recording medium 10. As is appreciated, head 12b does not
reproduce any useful signal information once it departs from the recording
medium. A comparison of FIGS. 2A and 2B indicates the overlapping portion
of the vertical blanking intervals recorded on adjacent tracks. These
overlapping portions are reproduced simultaneously by heads 12a and 12b.
However, the head switch control apparatus shown in FIG. 1 prevents both
reproduced signals from being applied simultaneously to demodulator 48.
As motor 18 drives shaft 16 to rotate heads 12a and 12b, magnet 20,
included in the position pulse generator, likewise is rotated. When head
12a arrives at the beginning portion of a track, pickup coil 22a senses
the corresponding position of magnet 20 so as to produce the pulse shown
in FIG. 2C. Since head 12a rotates into contact with recording medium 10
at the vertical blanking interval of the recorded field of video signals,
the pulse (FIG. 2C) produced by coil 22a is generated at approximately the
start of this vertical blanking interval. Pulse amplifier 24a shapes the
pickup-coil generated pulse as shown in FIG. 2D, and this shaped pulse is
delayed by delay circuit 26a so as to insure that the delayed pulse (FIG.
2H) will occur well within the vertical blanking interval and, preferably,
during the first set of equalizing pulses. The delayed pulse of FIG. 2H is
applied to the reset input of flip-flop circuit 28 so as to reset this
flip-flop circuit to its second state, as represented by the output signal
shown in FIG. 2I.
As motor 18 continues to drive shaft 16, head 12a reproduces the remaining
field recorded in the track which is scanned thereby, as represented by
FIG. 2B. As this head scans the end portion of the track, head 12b rotates
into position to commence scanning the next adjacent track, as shown in
FIG. 2A. Accordingly, head 12b commences to reproduce the signals recorded
in the adjacent track, as indicated by the slope 66 in FIG. 2A. As was
discussed previously, the vertical blanking interval reproduced by head
12b in the track scanned thereby is the same as the vertical blanking
interval reproduced by the head 12a recorded in the preceding track. This
period of overlap ends when head 12a departs from recording medium 10, as
represented by slope 68 in FIG. 2B.
Coincident with the scanning of the track by head 12b, magnet 20 rotates
past pickup coil 22b which detects this magnet to produce the position
pulse shown in FIG. 2E. This pulse is shaped and amplified in amplifier
24b (FIG. 2F) and is delayed by delay circuit 26b so as to produce the
delayed position pulse shown in FIG. 2G. The purpose of delay circuit 26b
is similar to that of delay circuit 26a, that is, to insure that the
position pulse derived from pickup coil 22b occurs during the vertical
blanking interval reproduced by head 12b and, preferably, during the first
set of equalizing pulses. The position pulse shown in FIG. 2G is applied
to the set input of flip-flop circuit 28 so as to set this flip-flop
circuit to its first state, resulting in the output signal shown in FIG.
2I.
It may be thought that this signal (FIG. 2I) produced by flip-flop circuit
28 can be used to control switching circuits 44a and 44b. That is, the
negative transition in this signal could be used to close switching
circuit 44a and concurrently open switching circuit 44b. Similarly, the
positive transition in this signal could be used to open switching circuit
44a and concurrently close switching circuit 44b. However, this is not
desirable for the reasons now explained. A transient pulse, or noise, is
produced when the respective switching circuits are actuated or deactuated
(i.e., closed or opened). These transients are superimposed onto the video
signals which then are reproduced by heads 12a and 12b and supplied to
demodulator 48. Because of tape shrinkage, or change in the rotary speed
of the transducer heads or other parameters, or in the event that the
signals recorded on medium 10 are recorded by a different recording system
than the system which is used to reproduce these signals, the times of
occurrence of the negative and positive transitions shown in FIG. 2I are
not necessarily fixed with respect to the reproduced vertical blanking
interval. That is, the foregoing factors may result in the actuation and
deactuation of switching circuits 44a and 44b at some arbitrary time
during the vertical blanking intervals. This has the effect of
superimposing transient noise into correspondingly arbitrary locations in
the vertical blanking intervals. While such transient noise may be
tolerated in, for example, home video playback systems, it is not
acceptable in a reproduced video signal that is to be processed for, for
example, a television broadcast. In addition, in a practical system, the
demodulated video signal produced by demodulator 48 may be applied to a
time-base correcting circuit which functions to correct time-base errors
which may be caused by tape shrinkage, tape stretching, changes in tape
speed, or any of the other above-mentioned factors. Such time-base error
correction depends upon sensing the horizontal synchronizing pulses as
well as the equalizing pulses and vertical synchronizing pulses included
in the vertical blanking interval of the demodulated video signal. If
transient noise occurs at an arbitrary location between, for example,
successive horizontal synchronizing pulses or between successive
equalizing pulses, the time-base correcting circuit may erroneously
interpret such transient noise as a synchronizing pulse. This
interpretation by the time-base correcting circuit would inhibit proper
time-base correction.
This problem is overcome by the head switching control apparatus shown in
FIG. 1. The signal produced by flip-flop circuit 28 is applied to
synchronizing circuit 30 which is synchronized with the synchronizing
pulses separated from the demodulated composite video signal by
synchronizing signal separator circuit 50. More particularly, and with the
assumption that synchronizing circuit 30 is, in one embodiment, a
timing-pulse controlled flip-flop circuit, such as a D-type flip-flop
circuit, flip-flop circuit 30 changes its state to correspond to the state
of flip-flop circuit 28, as represented by the signal (FIG. 2I) applied
thereto by flip-flop circuit 28, only when a separated synchronizing pulse
is applied to its T input. Thus, if flip-flop circuit 28 changes its state
at some arbitrary time between, for example, the second and third
equalizing pulses included in the first set of equalizing pulses provided
in the vertical blanking interval reproduced by head 12a, flip-flop
circuit 30 does not change its state until the third equalizing pulse
(FIG. 2B) is applied to its T input by synchronizing signal separator
circuit 50. At that time, flip-flop circuit 30 changes its state, as shown
in FIG. 2J. Similarly, when flip-flop circuit 28 is set to its first state
by the delayed position pulse shown in FIG. 2G, flip-flop circuit 30 does
not follow this change of state until the third equalizing pulse included
in the vertical blanking interval reproduced by head 12b is applied to its
T input, as shown in FIG. 2J.
Therefore, it is seen from FIG. 2J that switching pulses produced by
flip-flop circuit 30 are synchronized with the equalizing pulses which are
separated from the reproduced composite video signal. Hence, switches 44a
and 44b are actuated and deactuated at the same relative time, that is,
substantially in coincidence with an equalizing pulse, regardless of when
flip-flop circuit changes its state. That is, although flip-flop circuit
28 may change its state at any arbitrary time between successive
equalizing pulses, flip-flop circuit 30 is synchronized so as to change
its state only in synchronism with an equalizing pulse. Consequently,
transient noise which is produced by the actuation and deactuation of the
switching circuits 44a and 44b is superimposed onto the reproduced
composite video signal in coincidence with an equalizing pulse included in
the vertical blanking interval. This avoids the problem of misinterpreting
such transient noise by a time-base correcting circuit. Hence, time-base
errors can be readily corrected. Also, since a time-base error correcting
operation essentially reshapes the various synchronizing pulses, these
reshaped pulses will be free of the transient noise which is superimposed
onto the equalizing pulse. The resultant composite video signal is
satisfactory for television broadcasting.
While the present invention has been particularly shown and described with
reference to a preferred embodiment thereof, it will be readily apparent
to one of ordinary skill in the art that various changes and modifications
in form and details can be made. For example, synchronizing circuit 30 may
be comprised of a gated flip-flop circuit which functions to synchronize
the output of flip-flop circuit 28 (FIG. 2I) with a separated
synchronizing pulse. As another example, although the adjustability of
delay circuits, 26a and 26b is desirable so as to account for a wide range
of tape shrinkage or tape stretching or tape speed changes or other
parameters which may affect the relative time of occurrence of a position
pulse, the delay imparted by these delay circuits may be fixed, but may be
of a duration greater than that illustrated by FIGS. 2G and 2H. As yet
another example, the position pulse generator comprised of magnet 20 and
pickup coils 22a and 22b may be replaced by other equivalent position
sensing transducers, such as an optical position sensor, or the like.
It is intended that the appended claims be interpreted as including the
foregoing as well as all other changes and modifications which do not
depart from the spirit and scope of the present invention.
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