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JP2008103966

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JP2008103966
To reduce the steady heat generation and power consumption of a conductor line of a
diaphragm. A driving pulse signal is output from a switching amplifier to a conductor line 2
formed on a pair of opposed diaphragms 1, and output timing of at least one of rising and / or
falling edge of the driving pulse signal is An electromagnetic force that is correlated with the
level of the audio signal is applied to the diaphragm 1 in accordance with the level of the audio
signal to vibrate the diaphragm 1 and perform acoustic output. [Selected figure] Figure 1
Flat speaker driving method and flat speaker system
[0001]
The present invention relates to a flat speaker driving method and a flat speaker system.
[0002]
Many flat panel loudspeakers are driven in the same manner as ordinary electrodynamic
loudspeakers, except that the diaphragm that strikes the sound emitting surface is a flat plate.
That is, by supplying a current corresponding to an audio signal to the voice coil inserted in the
magnetic gap, a driving force having a correlation with the audio signal is generated, and the
voice coil is connected via a bobbin or a voice coil The electroacoustic conversion is performed
by moving the diaphragm directly connected to the.
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1
[0003]
However, in the above, the diaphragm is required to have a sufficient strength to support the
voice coil and the bobbin, and the diaphragm itself can not be extremely thin. Therefore, in order
to vibrate the diaphragm, a corresponding force is required, and there is a problem that even
delicate sounds can not be faithfully reproduced.
[0004]
In order to solve this problem, the following device has already been proposed that utilizes the
force acting between two currents (see, for example, Patent Document 1). In this device, the
diaphragm and the fixed plate are disposed in an opposing manner, and a coil serving as a
conductor line is disposed on both the plates, and the two coils are opposed to each other, and an
audio signal supplied to the coil of the diaphragm When the value is a positive value, current in
the same direction flows through the coil of the fixed plate, the diaphragm is displaced forward,
and when the audio signal has a negative value, the current in the reverse direction is
transmitted to the coil of the fixed plate Flows, and the diaphragm is displaced rearward.
[0005]
By the way, in said thing, although use of a linear amplifier is assumed regarding power
amplification of an audio signal, the efficiency of a linear amplifier was low and there existed a
problem that reduction of power consumption was difficult.
[0006]
Patent 3349647
[0007]
An object of the present invention is to provide a flat speaker driving method and a flat speaker
system capable of reducing power consumption.
[0008]
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2
In order to achieve the above object, the feature of the driving method of the flat speaker of the
present invention is that a driving pulse signal is output from a switching amplifier to a
conductor line formed on a pair of opposed diaphragms, and a driving pulse is generated. The
output timing of at least one rising and / or falling edge of the signal is changed according to the
level of the audio signal, and the duration of the attraction acting on both conductor lines and the
conductor lines of both conductor lines are changed on the conductor lines of both diaphragms.
The ratio of the duration of the repulsive force acting on the surface is an electromagnetic force
that is correlated with the level of the audio signal to cause the diaphragm to vibrate to perform
an acoustic output.
Also, the features of the flat loudspeaker system of the present invention are:
A pair of opposing diaphragms on which conductor lines are formed, B.
An audio signal is input, and a drive pulse signal is output to the conductor line of each
diaphragm, and the output timing of at least one of the rising and / or falling edge of the drive
pulse signal changes according to the level of the audio signal. A switching amplifier which
causes the conductor lines of both diaphragms to have an electromagnetic force whose ratio of
the duration of attractive force acting on both conductor lines to the duration of repulsion acting
on both conductor lines is correlated with the level of the audio signal The point is to have When
the input audio signal is 0, the output timings of the rising and falling edges of each drive pulse
signal may be shifted by 1⁄4. Also, the switching amplifier is a. Means for generating a reference
pulse signal which is sawtooth wave; b. Means for comparing the levels of the reference pulse
signal and the audio signal, and outputting a pulse width modulation signal whose pulse width is
modulated according to the level of the audio signal; Means for converting the reference pulse
signal into a rectangular wave and outputting a control pulse signal as one of the drive pulse
signals, and setting the frequency of the control pulse signal to 1/2 of the reference pulse signal;
There is also a means for outputting the other drive pulse signal and setting the other drive pulse
signal to a predetermined level when the levels of both the pulse width modulation signal and the
control pulse signal are different. Furthermore, the switching amplifier is a. A unit for generating
a reference pulse signal which is a rectangular wave and is one driving pulse signal; A means for
converting the reference pulse signal and outputting a control pulse signal in the form of a
triangular wave; Means for comparing the levels of the control pulse signal and the audio signal,
and outputting a pulse width modulated signal whose pulse width is modulated according to the
level of the audio signal; It may also have means for taking the output of the rising edge of the
pulse width modulation signal as a trigger and outputting the other drive pulse signal whose
frequency is equal to the control pulse signal. Also, the switching amplifier is a. Means for
generating a reference pulse signal which is a rectangular wave and is one of the drive pulse
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signals; A means for converting the reference pulse signal and outputting a control pulse signal
in the form of a triangular wave; Means for comparing the levels of the control pulse signal and
the audio signal, and outputting a first pulse width modulation signal whose pulse width is
modulated according to the level of the audio signal; A means for inverting the audio signal to
output an inverted audio signal; Means for comparing the levels of the control pulse signal and
the inverted audio signal and outputting a second pulse width modulated signal whose pulse
width is modulated according to the level of the inverted audio signal;
The other drive pulse signal is output, the output timing of the rising edge of this drive pulse
signal is made the same as the falling edge of the first pulse width modulation signal, and the
output timing of the falling edge of the drive pulse signal is the second pulse width modulation It
may have means to be identical to the falling edge of the signal. Furthermore, an amplification
circuit that amplifies the drive pulse signal and outputs it to the conductor line may be provided.
[0009]
According to the present invention, although the drive pulse signal having correlation with the
audio signal, that is, the alternating current is output from the switching amplifier to both
conductor lines, the frequency of the drive pulse signal of the switching amplifier is set to a
relatively high frequency. Therefore, the impedance of the conductor line with respect to the
alternating current is high. Therefore, when there is no input of the audio signal, the conductor
line hardly generates heat, and steady heat generation of the conductor line can be reduced. In
addition, since a high efficiency switching amplifier is used, power consumption can be reduced.
Furthermore, since a magnetic circuit using magnets or metal parts is not used, the weight of the
speaker can be reduced.
[0010]
Hereinafter, the first example of the embodiment of the present invention will be described based
on the drawings of FIGS. 1 to 4. The flat speaker system includes the flat speaker shown in FIGS.
1 and 2 and the switching amplifier (speaker drive shown in FIG. Device).
[0011]
The flat speaker includes, for example, a pair of flat diaphragms 1 formed of ceramic or the like,
and these diaphragms 1 are disposed in parallel on the same projection plane and opposed to
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each other.
Normally, one diaphragm 1 is a fixed plate fixed to a frame or the like, and the other diaphragm
1 is held by the one diaphragm 1 via a spacer. In this example, both are used for convenience.
The plate is described as a functionally equivalent diaphragm 1. Conductor lines (conductors,
conductors, wires) 2 are formed in the same pattern on each diaphragm 1, and both conductor
lines 2 face each other. As shown in FIG. 1, when a drive current in the opposite direction flows
through both conductor lines 2, a repulsive force due to Lorentz force (electromagnetic force)
acts between the conductor lines 2 between the diaphragms 1, and As shown in 2, when drive
current in the same direction flows through both conductor lines 2, an attractive force due to
Lorentz force acts between the conductor lines 2 of both diaphragms 1, and this repulsive force
and attractive force in the speaker, It is made to substantially correspond to the target acoustic
radiation direction. The conductor line 2 has a straight horizontal portion 2A disposed in the
width direction of the diaphragm 1 and a curved connection portion 2B connecting one end of
the adjacent horizontal portion 2A. The conductor line 2 may be formed by affixing a conductor
to the diaphragm 1, or may be formed on the diaphragm 1 by etching in the form of a
transparent electrode. The material of the diaphragm 1 and the conductor line 2 is preferably
lightweight.
[0012]
The switching amplifier converts the input analog audio signal into a digital audio signal, that is,
a drive pulse signal and amplifies it, and outputs it as a drive signal of the diaphragm 1 to both
conductor lines 2, but in this case The output timing of at least one rising and / or falling edge of
the pulse signal is also referred to as the potential (voltage) of the audio signal. The same applies
below. The diaphragm 1 is made to vibrate by changing according to the level). The driving
power for a certain period is proportional to the on / off time ratio of the output stage of the
switching amplifier. The switching amplifier performs the following operation. That is, when the
input audio signal has a positive value, the potential of the pulse output of the switching
amplifier connected to one conductor line 2 and the potential of the pulse output of the
switching amplifier connected to the other conductor line 2 are The time of the same potential is
made longer than the time of the opposite potential, and when the input audio signal has a
negative value, the time where the above two potentials are opposite is made longer than the
time of the same potential. Do the action. The switching amplifier performing such an operation
includes a sawtooth wave generation circuit 4, a comparator 5, a D flip flop 6, an exclusive OR
gate 7, and amplification circuits 8, 9 and the like.
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[0013]
The sawtooth wave generation circuit 4 is exemplified as a reference pulse signal generation
circuit and, as shown in FIG. 4, is a sawtooth wave having a frequency sufficiently higher than the
frequency of the audio signal A input to the switching amplifier. A reference pulse signal B is
generated. In the present example, the rising of the waveform of the reference pulse signal B is
relaxed and the falling is made steep.
[0014]
The comparator 5 is exemplified as a pulse width modulation signal output circuit, and an audio
signal is inputted to one (plus side) input terminal thereof, and a sawtooth wave is generated to
the other (minus side) input terminal Circuit 4 is connected. As shown in FIG. 4, the comparator 5
compares the potential levels of the audio signal A and the reference pulse signal B, and a pulse
width modulation signal D whose pulse width is modulated (PWM) according to the potential
level of the audio signal A. Output When the level of the audio signal A is higher than that of the
reference pulse signal B, the pulse width modulation signal D becomes high level.
[0015]
D flip-flop 6 is exemplified as rectangular wave generating circuit 4, sawtooth wave generating
circuit 4 is connected to inverted clock input terminal bar CK, and positive voltage + Vcc is
applied to data input terminal D, as shown in FIG. As shown in 4, the control pulse signal C in
which the frequency is a half wave of the reference pulse signal B is output from the output
terminal Q using the output of the falling edge of the reference pulse signal B as a trigger, This is
used as one drive pulse signal.
[0016]
The exclusive OR gate (EX-OR gate) 7 is exemplified as a drive pulse signal output circuit, and the
output terminal of the comparator 5 and the output terminal Q of the D flip flop 6 are connected
to the input terminals thereof. As shown in FIG. 4, the target OR gate 7 outputs the other drive
pulse signal E which is an exclusive OR (EX-OR) of the pulse width modulation signal D and the
control pulse signal C.
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That is, in the drive pulse signal, the output timing of the rising and / or falling edge is controlled
according to the potential level of the audio signal, and the potential levels of both the pulse
width modulation signal D and the control pulse signal C are different. In this case, the drive
pulse signal E is at a predetermined level, that is, a high level.
[0017]
The output terminal of the exclusive OR gate 7 or the output terminal Q of the D flip flop 6 is
connected to the input terminal of each of the amplifier circuits (amplifiers) 8 and 9, and is used
as the input drive pulse signal E and drive pulse signal. Control pulse signal C is amplified and
output. The output terminal of each amplifier circuit 8 is connected to the conductor line 2 of
each diaphragm 1.
[0018]
According to the above configuration example, the drive pulse signal E is input as the drive
current to one of the conductor lines 2 of both diaphragms 1 and the control pulse signal C,
which is the drive pulse signal as the drive current, is input to the other. Be done. In this case, as
shown in FIG. 1, when a drive current in the opposite direction flows through both conductor
lines 2, a repulsive force by Lorentz force acts between the conductor lines 2 of both diaphragms
1, and FIG. As shown, when drive current in the same direction flows through both conductor
lines 2, an attractive force due to Lorentz force acts between the conductor lines 2 of both
diaphragms 1. The Lorentz force acting between the conductor lines 2 of both diaphragms 1 has
a correlation with an exclusive OR of the drive pulse signal E and the control pulse signal C which
is used as the drive pulse signal as shown in FIG. (In fact, it has a correlation with the low-pass
component included in this exclusive OR. The same applies below. ). When the exclusive OR is at
high level, a repulsive force acts between the conductor lines 2 of both diaphragms 1, and when
the exclusive OR is at low level, an attractive force is generated between the conductor lines 2 of
both diaphragms 1. Works. The diaphragm 1 vibrates due to the repulsive force and the
attractive force, and an acoustic output is performed.
[0019]
FIGS. 5 and 6 show a second example of the embodiment of the present invention, and as shown
in FIG. 5, the switching amplifier includes a rectangular wave generation circuit 10, a triangular
wave generation circuit 11, and a comparator 12. A monostable multivibrator 13 and
amplification circuits 8 and 9 are provided.
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[0020]
The rectangular wave generation circuit 10 is exemplified as a reference pulse signal generation
circuit, and generates a reference pulse signal E which is a rectangular wave as shown in FIG.
The reference pulse signal E is one of the drive pulse signals, and the output terminal of the
rectangular wave generation circuit 10 is connected to the input terminal of the triangular wave
generation circuit 11.
[0021]
The triangular wave generation circuit 11 is exemplified as a control pulse signal output circuit,
and as shown in FIG. 6, the control pulse signal B converted from the reference pulse signal E
into a triangular wave whose waveform is an isosceles triangle is Output. When the reference
pulse signal E rises and outputs, the control pulse signal B becomes high level, and when the
reference pulse signal E falls and outputs, the control pulse signal B becomes low level.
[0022]
The comparator 12 is exemplified as a pulse width modulation signal output circuit, the audio
signal A is inputted to the plus side input terminal thereof, and the triangle wave generation
circuit 11 is connected to the minus side input terminal. The comparator 12 compares the
potential levels of the audio signal A and the control pulse signal B, and as shown in FIG. 6, a
pulse width modulation signal whose pulse width is modulated (PWM) according to the potential
level of the audio signal A. Output C When the level of the audio signal A is higher than that of
the control pulse signal B, the pulse width modulation signal C becomes high level.
[0023]
The monostable multivibrator 13 is exemplified as a drive pulse signal output circuit, and outputs
the other drive pulse signal D using the output of the rising edge of the pulse width modulation
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signal C as a trigger, as shown in FIG. The cycle of the drive pulse signal D is equal to the cycle of
the control pulse signal B and is fixed.
[0024]
The output terminal of the monostable multivibrator 13 or the output terminal of the rectangular
wave generation circuit 10 is connected to the input terminals of the amplification circuits 8 and
9.
[0025]
According to the above configuration example, the Lorentz force acting between the conductor
lines 2 of both diaphragms 1 is an exclusive OR of the drive pulse signal D and the reference
pulse signal E to be the drive pulse signal as shown in FIG. And have a correlation.
[0026]
FIGS. 7 and 8 show a third example of the embodiment of the present invention, and as shown in
FIG. 7, the switching amplifier includes the rectangular wave generation circuit 15, the triangular
wave generation circuit 16, and the first and second ones. It has comparators 17 and 18, a knot
gate 19, an OR gate 20, a D flip flop 21, and amplification circuits 8, 9 and the like.
[0027]
The rectangular wave generation circuit 15 is exemplified as a reference pulse signal generation
circuit, and as shown in FIG. 8, outputs a reference pulse signal F made into a rectangular wave.
The reference pulse signal F is used as one drive pulse signal, and the output terminal of the
rectangular wave generation circuit 16 is connected to the input terminal of the triangular wave
generation circuit 16.
[0028]
The triangular wave generation circuit 16 is exemplified as a first control pulse signal output
circuit, and as shown in FIG. 6, the first control in which the reference pulse signal F is converted
into a triangular wave whose waveform is an isosceles triangle The pulse signal C is output.
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[0029]
The first comparator 17 is exemplified as a first pulse width modulation signal output circuit. The
audio signal A is input to the positive side input terminal thereof, and the triangular wave
generation circuit 16 is connected to the negative side input terminal.
The first comparator 17 compares the potential levels of the audio signal A and the first control
pulse signal C, and as shown in FIG. 8, the pulse width is modulated (PWM) according to the
potential level of the audio signal A. A first pulse width modulation signal D is output.
When the level of the audio signal A is higher than that of the first control pulse signal C, the first
pulse width modulation signal D becomes high level.
[0030]
The knot gate (NOT gate, output inverting circuit, inverter) 19 is exemplified as an inverted audio
signal output circuit, and as shown in FIG. 6, the input audio signal A is inverted to generate an
inverted audio signal B. Output.
[0031]
The second comparator 18 is exemplified as a second pulse width modulation signal output
circuit, the output terminal of the NOT gate 19 is connected to the positive side input terminal
thereof, and the output of the triangular wave generation circuit 16 is connected to the negative
side input terminal. Terminal is connected.
The second comparator 18 compares the potential levels of the inverted audio signal B and the
control pulse signal, and as shown in FIG. 8, the pulse width is modulated (PWM) according to
the potential level of the inverted audio signal B. A 2-pulse width modulation signal E is output.
When the level of the inverted audio signal A is higher than that of the first control pulse signal
C, the second pulse width modulation signal E becomes high level.
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[0032]
The OR gate (OR gate) 20 is exemplified as a second control pulse signal output circuit, and the
output terminal of the second comparator 18 and the output terminal of the rectangular wave
generation circuit 15 are connected to the input terminal thereof. , And outputs a second control
pulse signal. When the potential levels of both the second pulse width modulation signal E and
the reference pulse signal F are different, the second control pulse signal is set to a
predetermined level, that is, a high level.
[0033]
The D flip flop 21 is exemplified as a drive pulse signal output circuit, the output terminal of the
first comparator 17 is connected to the inverted clock input terminal bar CK, and the rectangular
wave generating circuit is connected to the data input terminal D. An output terminal 15 is
connected, an output terminal of the OR gate 20 is connected to the reset terminal R, and the
other drive pulse signal G is output from the output terminal Q. The output timing of the rising
edge of the drive pulse signal G is the same as the falling edge of the first pulse width modulation
signal D, and the output timing of the falling edge of the drive pulse signal G is the second pulse
width modulation signal E. It is identical to the falling edge.
[0034]
The output terminal Q of the D flip flop 21 or the output terminal of the rectangular wave
generation circuit 15 is connected to the input terminal of each amplifier circuit.
[0035]
According to the above configuration example, the Lorentz force acting between the conductor
lines 2 of both the diaphragms 1 is the exclusive OR of the drive pulse signal G and the reference
pulse signal F to be the drive pulse signal as shown in FIG. And have a correlation.
[0036]
10 to 14 illustrate the operation of each of the above examples of the present invention more
specifically.
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That is, assuming that the sign of one of the diaphragms is A and the sign of the other diaphragm
is B, as shown in FIG. 10, drive currents (signals in the same direction to the conductor lines 2 of
both diaphragms A and B) When I1 and I2 flow, magnetic lines of force in the same direction are
generated around each of the conductor lines 2 as indicated by the alternate long and short
dashed lines and dotted lines in FIG.
Thereby, magnetic line of force E1, E2 of the opposite direction by the drive current I1, I2 which
flows to the other conductor line 2 acts on each conductor line 2 as shown by a dashed dotted
line or dotted line in FIG. As indicated by thick lines in FIG. 10, an attractive force by Lorentz
force acts between the conductor lines 2 of both the diaphragms A and B due to electromagnetic
induction by the drive currents I1 and I2 and the magnetic force lines E1 and E2.
[0037]
Further, as shown in FIG. 11, when drive currents I1 and I2 in the opposite direction flow
through the conductor lines 2 of both diaphragms A and B, the dashed lines in FIG. As shown by
the dotted lines, magnetic lines of force in the opposite direction are generated. As a result,
magnetic line of force E1, E2 in the same direction by the drive current I1, I2 flowing through the
other conductor line 2 acts on each conductor line 2 as indicated by the one-dot chain line or
dotted line in FIG. As shown by thick lines in FIG. 11, a repulsive force by Lorentz force acts
between the conductor lines 2 of both the diaphragms A and B by electromagnetic induction by
the drive currents I1 and I2 and the magnetic force lines E1 and E2.
[0038]
Further, as shown in FIGS. 12 to 14, the input audio signal is V-sig, and the period of the drive
current flowing through the conductor line 2 of the diaphragm A is τ, and flows through the
conductor line 2 of the diaphragms A and B. The rise (or fall) timing shift of the drive current is
τ ', the duration of the repulsive force acting between the conductor lines 2 of both diaphragms
A and B is T1, and the conductor line 2 of both diaphragms A and B is Assuming that the
duration of attractive force acting is T2, as shown in FIG. 12, when the input audio signal V-sig is
larger than 0, T1> T2 (τ '> τ / 4). . Further, as shown in FIG. 13, when the input audio signal Vsig is 0, T1 = T2 (τ '= τ / 4). Further, as shown in FIG. 14, when the input audio signal V-sig is
smaller than 0, T1 <T2 (τ '<τ / 4).
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[0039]
Thus, it is one of the features of the present invention that the period of each drive pulse is
shifted by 1⁄4 when the input audio signal is 0. As a result, when the input audio signal is zero,
T1 = T2, and the average of the force (exclusive logic) generated between the conductor lines 2
can be zero.
[0040]
In the above embodiment, although the cycle of one drive pulse signal is constant, as shown in
FIG. 9, one of the drive pulse signals B and C rises according to the positive or negative of the
input audio signal A. And / or the falling output timing may be changed. In FIG. 9, when the audio
signal A is negative, the output timing of the rising and / or falling of one drive pulse signal C is
changed, and when the audio signal A is positive, the other drive pulse signal B is changed.
Changing the output timing of the rising and / or falling of the Then, the exclusive OR of both
drive pulse signals B and C as shown in FIG. 9 and the Lorentz force acting between the
conductor lines 2 of both diaphragms 1 have a correlation.
[0041]
It is an explanatory view showing the 1st example of an embodiment of the invention. It is
explanatory drawing which shows the operating state different from FIG. It is a block diagram
which shows the 1st example of embodiment of this invention. It is a wave form diagram which
shows the signal level etc. of each part of FIG. It is a block diagram which shows the 2nd example
of embodiment of this invention. It is a wave form diagram which shows the signal level etc. of
each part of FIG. It is a block diagram which shows the 3rd example of embodiment of this
invention. It is a wave form diagram which shows the signal level etc. of each part of FIG. It is a
wave form diagram showing the signal level etc. of other examples of an embodiment of the
invention. It is an explanatory view explaining concrete operation of each above-mentioned
example of the present invention. It is an explanatory view explaining concrete operation of each
above-mentioned example of the present invention. It is an explanatory view explaining concrete
operation of each above-mentioned example of the present invention. It is an explanatory view
explaining concrete operation of each above-mentioned example of the present invention. It is an
explanatory view explaining concrete operation of each above-mentioned example of the present
invention.
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Explanation of sign
[0042]
1, A, B diaphragm 2 conductor line 4 sawtooth wave generation circuit 5, 12 comparator 6, 21 D
flip flop 7 exclusive OR gate 8, 9 amplification circuit 10, 15 square wave generation circuit 11,
16 triangular wave generation circuit 13 single Stable multivibrator 17, 18 1st and 2nd
comparators 19 knot gate 20 or gate
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