JP2009145660A - Impact detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic percussion instrument, eliminating malfunction and reducing the processing of a sound source device. <P>SOLUTION: When a first flag is set to 1 (S3:YES), the magnitude of vibration of a pad which has transmitted a sound generation designating signal is obtained based on a signal (a note on velocity) showing the impact strength included in the received sound generation designating signal, and the magnitude of the vibration is compared with the level of vibration converted by an A/D converter 13 and detected (S4). According to the comparison, it is determined whether the pad 1 is impacted (S5). That is, when the detected vibration level is higher than the impact strength showing the received sound generation designating signal, it is determined that the pad is impacted, and when the detected vibration level is lower than the impact strength showing the received sound generation designating signal, it is determined that another pad is impacted to propagate the vibration. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a hit detection device used in an electronic percussion instrument, and more particularly to a hit detection device that can eliminate malfunction and reduce processing of a sound source device.

  A hitting detection device that conventionally has a hitting surface hit by a stick or the like and instructs a sound source device to generate a musical sound corresponding to the hitting surface when detecting that a sensor provided on the hitting surface is hit Are known. FIG. 4 is a front view showing an appearance of a drum system 100 in which a conventional hit detection device and a sound source device are combined. The drum system 100 includes a drum stand 110 in which hollow pipes formed of a plurality of aluminum or the like are assembled into an arbitrary shape, four hit detection devices (hereinafter referred to as “pads”) 101 to 104, and a sound source device 120. And are assembled. Here, a case where four pads 101 to 104 are assembled is shown, but in addition to these four pads 101 to 104, an electronic bass drum, a plurality of electronic cymbals, an electronic hi-hat, and the like are also used as a system. The sensor output is input to the sound source device 120.

  FIG. 5 is a block diagram showing an electrical configuration of the drum system 100. Each of the four pads 101 to 104 is provided with a piezo sensor 11 for detecting vibration of the hitting surface. Each piezo sensor 11 is formed by a piezo element or the like, and converts vibration generated on the hitting surface into an analog electric signal. Thus, the output of each piezo sensor 11 is input to analog input terminals 127a to 127d provided in the sound source device 120, respectively. The sound source device 120 is mainly provided with a CPU 121, a ROM 122, a RAM 123, a sound source circuit 124, an operation element 125, and a display 126, and an output of the sound source circuit 124 includes an amplifier 130 and a speaker 140. Connected.

  The CPU 121 incorporates an A / D converter 121a, and the analog electric signals input to the analog input terminals 127a to 127d are sequentially converted into digital signals. The envelope is detected from each of the digital signals, the strength of the hit applied to each pad is detected, and the tone generator circuit 124 is controlled so as to generate a musical sound according to the detected hit strength. .

  In this process, when any of the striking surfaces of the pads 101 to 104 is hit, vibration generated by the hit is propagated to the other pads 101 to 104 via the drum stand 110 or the like, and the other pads 101 to 104 are hit. In 104, a malfunction may be generated in which vibration is detected even though no hit is made. Therefore, a technique for controlling the sound source device 120 so as not to cause this malfunction has been proposed.

In Japanese Examined Patent Publication No. 7-43589 (Patent Document 1), when the outputs of sensors provided on a plurality of hitting surfaces are input and vibrations are simultaneously detected by a plurality of sensors, The ratio is calculated, and the hitting surface of the pad that is actually hit is detected based on the difference or the ratio. Then, a tone is generated corresponding to the pad that has been determined to have been hit, and even if the pad hitting surface is detected to be vibrated, it is determined that the vibration is due to propagation from the hitting surface of another pad. With regard to, a technique for controlling so as not to generate a corresponding musical tone is described.
Japanese Examined Patent Publication No. 7-43589

  However, in the technique described in Patent Document 1 described above, the output of a plurality of sensors is input, and the vibration detected by the sensors is generated when the hitting surface corresponding to the sensor is struck. However, the sound source device also controls the sound that is generated or the sound that is being generated, etc. There is a problem that many processes are concentrated and the processing of the sound source device becomes enormous, delaying the start of the generation of musical sounds and making the control of musical sounds unnatural.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an impact detection device that can eliminate malfunction and reduce processing of a sound source device.

  In order to achieve the above object, a hit detection device according to claim 1 of the present invention includes a hitting surface, a sensor for detecting vibration of the hitting surface, and generation of a musical sound according to the vibration detected by the sensor. Output means for outputting a sound generation instruction signal to be directed to the sound source device, input means for inputting a sound generation instruction signal output by another impact detection device, vibration detected by the sensor, and the input A hit determination unit that compares the sound generation instruction signal input to the means and determines whether the hitting surface has been hit, and the output means determines that the hitting surface has been hit by the hitting determination unit In this case, a sound generation instruction signal is output.

  The hit detection device according to claim 2 is the hit detection device according to claim 1, wherein the 222222222 sound generation instruction signal includes intensity information indicating a level of vibration, and the hit determination means includes the vibration detected by the sensor. Is compared with the vibration level indicated by the intensity information included in the sound generation instruction signal input to the input means.

  The hit detection device according to claim 3 is the hit detection device according to claim 1 or 2, further comprising a timing unit that starts timing when a sound generation instruction signal is input to the input unit, and the hit determination unit includes the timing measurement unit. When the time counted by the means is within a predetermined time, it is determined whether or not the hitting surface has been hit.

  According to a fourth aspect of the present invention, in the hit detection device according to any one of the first to third aspects of the present invention, the hit detection device includes a wireless communication unit that wirelessly transmits and receives a sound generation instruction signal. A sound generation instruction signal is input from another impact detection device, and the output means outputs a sound generation instruction signal by the wireless communication means.

  The impact detection device according to claim 5 is the impact detection device according to any one of claims 1 to 4, wherein the impact detection device is detected by a conversion table storage means for storing a conversion table for converting a vibration level into intensity information, and the sensor. Intensity information acquisition means for acquiring intensity information corresponding to the level of vibration made by referring to a conversion table stored in the conversion table storage means, and the output means is acquired by the intensity information acquisition means A sound generation instruction signal including the intensity information is output.

  According to the hit detection device of the first aspect, the input means inputs the sound generation instruction signal output by the other hit detection device, and the hit determination means is input to the vibration detected by the sensor and the input means. The sound generation instruction signal is compared to determine whether the hitting surface has been hit. When a hit is made in another hit detection device, the vibration generated in the other hit detection device due to the hit is propagated, the sensor vibrates, and the sensor outputs an output signal, but the other hit detection device By inputting the output sound generation instruction signal, the output signal output from the sensor by the hit determination means is generated by hitting another hit detection device, or is generated by hitting the hitting surface of itself. Can be determined. The output means outputs a sound generation instruction signal to the sound source device when it is determined by the hit determination means that the hitting surface has been hit. Therefore, the sound source device only needs to generate a musical sound corresponding to the sound generation instruction signal when the sound generation instruction signal is input, and the hitting surface is hit among the outputs of the sensors input from a plurality of hit detection devices at the same time. Therefore, it is not necessary to determine whether the output is generated or not. Therefore, it is possible to prevent malfunctions and reduce the processing in the sound source device. By reducing the processing of the sound source device, the sound source device can quickly generate a musical sound by inputting a sound generation instruction signal, and can prevent the musical sound being generated from being unnaturally controlled.

  Further, the sound generation instruction signal is transmitted by the output means, and if it is transmitted even though its own hitting surface is not hit, an unnecessary signal is transmitted to the communication path. Transmission of useless signals on the communication path can be suppressed, and the communication path can be prevented from being congested.

  According to the hit detection device of claim 2, in addition to the effect produced by the hit detection device of claim 1, the sound generation instruction signal includes intensity information indicating the level of vibration. Since the determination is made by comparing the detected vibration level with the vibration level indicated by the intensity information included in the sound generation instruction signal input to the input means, the vibration detected by the sensor is the hitting surface of itself. There is an effect that it is possible to determine whether it is generated by hitting or another hit detection device.

  According to the hit detection device according to claim 3, in addition to the effect produced by the hit detection device according to claim 1 or 2, the hit detection means comprises a timing means for starting timing when a sound generation instruction signal is input to the input means. Determines whether the hitting surface has been hit when the time measured by the time measuring means is within a predetermined time. Immediately after inputting the sound generation instruction signal, vibration is propagated from the other hit detection device, so that only the vibration detected within the predetermined time is the target of determination by the hit determination means, and is detected outside this predetermined time. The vibration can be prevented from being determined by the hit determining means. Therefore, there is an effect that it is possible to appropriately determine whether or not the hit has been performed.

  According to the impact detection device of claim 4, in addition to the effect of the impact detection device according to any of claims 1 to 3, the impact detection device includes wireless communication means that wirelessly transmits and receives a sound generation instruction signal, and the input means includes: The sound generation instruction signal is input from the other impact detection device by the wireless communication means, and the output means outputs the sound generation instruction signal by the wireless communication means, so that a plurality of impact detection devices and sound source devices can communicate with each other. There is no need for wiring. Moreover, since it is not connected with a cable etc., an installation place can be changed easily and there exists an effect that installation is easy.

  Further, although the sound generation instruction signal is transmitted by the wireless communication unit, wasteful power consumption by the wireless communication unit occurs if transmission is performed even though the hitting surface is not hit. According to this, wasteful power consumption by the wireless communication means can be suppressed. When the impact detection device is driven by a battery, it can be used for a long time by suppressing the consumption of power of the battery.

  According to the hit detection device of the fifth aspect, in addition to the effect exerted by the hit detection device according to any one of the first to fourth aspects, the conversion table storage means converts the vibration level into a strength information. The intensity information acquisition means stores the intensity information corresponding to the vibration level detected by the sensor by referring to the conversion table stored in the conversion table storage means. Therefore, there is no need to acquire intensity information of the generated musical sound in the sound source device, and there is an effect that processing in the sound source device can be reduced.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing an electrical configuration of the pad 1, the pad 2, and the sound source device 30 in the embodiment of the present invention. The pad 1 and the pad 2 have the same configuration. For example, the pad 1 is set to function as a snare drum, and the pad 2 is set to function as a tom-tom. Here, the pad 1 will be described below.

  The pad 1 is an impact detection device that can eliminate malfunctions and reduce the processing of the sound source device. The A / D converter 13 is mainly provided.

  The CPU 2, the ROM 3, the RAM 4, the operation element 5, the wireless transmission / reception circuit 6, and the A / D converter 13 are connected to each other by a bus line.

  The piezo sensor 11 is a sensor that is affixed to the back surface of a striking surface to be struck by the pad 1 and outputs an alternating voltage in response to vibrations applied to the striking surface by a player striking the striking surface. . One end of the piezo sensor 11 is grounded, and the output of the other end is connected to the input of the compression circuit 12. The compression circuit 12 is a circuit that rectifies the AC voltage output from the piezo sensor 11 and adjusts the envelope level of the signal to a voltage level that can be input to the A / D converter 13.

  The wireless transmission / reception circuit 6 includes an antenna 7 and can wirelessly communicate with other pads 2 and the sound source device 30. As a communication method, a method such as FDMA (Frequency Division Multiple Access), TDMA (Time Division Multiple Access), or CDMA (Code Division Multiple Access) is used. be able to.

  The CPU 2 controls each part of the pad 1 according to fixed values and programs stored in the ROM 3 and the RAM 4 or various control signals transmitted / received via the wireless transmission / reception circuit 6. The operation element 5 is a knob or switch that allows the player to arbitrarily set various parameter values of the pad 1. For example, a volume knob that sets the sensitivity of the pad or a plurality of pads are used. In addition, there is a switch for setting a device number (channel number) for identifying each pad.

  When the CPU 2 detects that the striking surface has been hit, the CPU 2 controls the wireless transmission / reception circuit 6 to transmit a sound generation instruction signal (hit signal). This sound generation instruction signal is a digital signal conforming to a note-on message defined by the MIDI standard. The note-on message includes a status for instructing the start of sound generation, a MIDI channel for identifying the device, a note number for specifying the pitch of the pressed key (in the case of a percussion instrument, the type of percussion instrument), and a key press Note-on velocity indicating the intensity of the. The MIDI channel and the note number are set in advance by the above-described operator 5.

  Further, the CPU 2 is provided with a timer 2a, and when the sound generation instruction signal is received from another pad, the time is started and a flag stored in the RAM 4 is set, and the time measured by the timer 2a is set to a predetermined time (for example, 1 msec), the flag is reset. If the pad 1 detects vibration while the flag is set, it is determined whether the vibration is caused by striking its own pad or by striking another pad. When it is determined that the vibration is caused by the impact of the pad, the sound generation instruction signal is transmitted. When it is determined that the vibration is caused by the other pad being struck, the sound generation instruction signal is transmitted. do not do.

  In this way, when the vibration is detected in the pad 1, it is possible to reduce the processing in the sound source device 30 and to transmit the sound from the pad 1 to the sound source device 30. It is possible to omit sending an unnecessary signal on the route to be performed. In particular, when the transmission path is performed wirelessly and the pad 1 is driven by a battery, the power consumed by performing transmission can be reduced, and the battery can be used for a long time.

  The ROM 3 is a non-rewritable memory that stores various control programs executed by the CPU 2 and fixed value data referred to when the programs are executed. As the fixed value data, a velocity curve 3a that is referred to when obtaining a note-on velocity value corresponding to the vibration level detected by the piezo sensor 11 is stored. A plurality of types of velocity curves 3a are stored corresponding to the types of percussion instruments, and the velocity curve 3a corresponding to the set percussion instrument is referred to.

  The RAM 4 is a rewritable memory for temporarily storing various data when the CPU 2 executes a control program stored in the ROM 17 or the like, and the above-mentioned flag is stored in the flag memory 4a.

  The sound source device 30 is a device used by being connected to the pad 1 by wireless communication, and is controlled based on the sound source control signal transmitted from the pad 1 and emits a musical sound from the speaker 39. The sound source device 30 mainly includes a wireless transmission / reception circuit 32, a CPU 33, a ROM 34, a RAM 35, an operator 36, and a sound source circuit 37.

  The wireless transmission / reception circuit 32 includes an antenna 31 and performs wireless communication with the electronic musical instrument 1. The wireless transmission / reception circuit 32 and the antenna 31 have the same configuration as the wireless transmission / reception circuit 6 and the antenna 7 provided in the pad 1.

  The CPU 33 is connected to each other by a ROM 34, a RAM 35, an operator 36, a sound source circuit 37, a wireless transmission / reception circuit 32, and a bus line. The output of the sound source circuit 37 is connected to an amplifier 38, and the output of the amplifier 38 is connected to a speaker 39.

  The CPU 33 controls each unit of the sound source device 30 according to fixed values and programs stored in the ROM 34 and RAM 35, or a sound source control signal and various control signals transmitted / received via the wireless transmission / reception circuit 32. The ROM 34 is a non-rewritable memory that stores various control programs executed by the CPU 33 and fixed value data referred to when the programs are executed. The RAM 35 is a rewritable memory for temporarily storing various data when the CPU 33 executes a control program stored in the ROM 34 or the like.

  The tone generator circuit 37 is a dedicated circuit for generating musical sounds formed by LSI. When a signal instructing the start of generation of musical sounds is input from the CPU 33, generation of a digital signal of musical sounds corresponding to the instruction is started. When a signal instructing the stop of the generation of a musical sound is input, the generated musical sound is stopped. When a percussion instrument sound is generated, a tone color tone corresponding to the note number is generated. The analog sound signal output from the tone generator circuit 37 is amplified by the amplifier 38 and emitted from the speaker 39.

  Next, processing executed by the CPU 2 of the pad 1 will be described with reference to FIG. FIG. 2 is a flowchart showing the main process of the pad 1. This main process is started when the power of the pad 1 is turned on, and is repeatedly performed until the power is turned off.

  When the power of the pad 1 is turned on, or when the power of another pad is turned on, the setting information such as which MIDI channel is set to which other pad is assigned to which percussion instrument is mutually shared. Exchanged. Also, when these settings are changed by the operator in each pad, the changed information is notified to the other pads.

  In this main process, first, a digital amplitude value indicating the magnitude of vibration detected by the piezo sensor 11 and converted by the A / D converter 13 is read (S1). It is determined whether or not the read digital value exceeds a predetermined threshold (S2). If the read digital value exceeds the predetermined threshold (S2: Yes), a flag stored in the flag memory 4a is stored. It is determined whether it is set to 1 (S3). This flag is set to 0 when the power of the pad 1 is turned on.

  When the flag is set to 1 (S3: Yes), the magnitude of the vibration of the pad that has transmitted the sound generation instruction signal based on the signal (note on velocity) indicating the striking strength included in the received sound generation instruction signal Then, the magnitude of the vibration is compared with the level of vibration detected by conversion by the A / D converter 13 (S4). As described above, the ROM 3 of the pad 1 stores a plurality of velocity curves 3a corresponding to the types of percussion instruments. The type of percussion instrument set to the pad that has transmitted the sound generation instruction signal is determined from the note number included in the sound generation instruction signal, and is generated at that pad by referring to the velocity curve 3a corresponding to the type of the percussion instrument. The magnitude of the vibration that has occurred can be obtained.

  By this comparison, it is determined whether or not the pad 1 has been hit (S5). That is, if the detected vibration level is larger than the striking strength indicated by the received sound generation instruction signal, it is determined that the pad has been hit, but the detected vibration level is determined by the received sound generation instruction signal. If it is smaller than the striking strength indicated by, it is determined that vibration has been propagated by striking another pad.

  If it is determined that the pad has been struck (S5: Yes), or if it is determined that the flag is not 1 in the determination process of S3 (S3: No), it is determined that this pad has been struck. The note-on velocity value corresponding to the detected vibration level is obtained by referring to the velocity curve 3a corresponding to the set percussion instrument type among the plurality of velocity curves 3a stored in the ROM 3. Next, a sound generation instruction signal is generated to instruct the tone color assigned to the pad 1 to be generated with the above note-on velocity value (S6), and then the sound generation instruction signal generated in the process of S6. Is transmitted by the wireless transmission / reception circuit 6 (S7).

  When it is determined in the determination process of S2 that the vibration level is not greater than the threshold value (S2: No), or when it is determined that the pad is not hit in the determination process of S5 (S5: No), or S7 When the process is completed, it is determined whether or not a sound generation instruction signal for instructing the start of sound generation is received from another pad (S8). When a sound generation instruction signal is received from another pad (S8: Yes), the flag is set to 1 (S9), and time measurement by the timer 2a is started (S10).

  Next, it is determined whether or not the time measured by the timer 2a exceeds a predetermined time (S11). If the predetermined time is exceeded (S11: Yes), the flag is reset (S12). The predetermined time is determined by the percussion intensity set in the sound generation instruction signal and the type of percussion instrument set in the pad that has transmitted the sound generation instruction signal.

  When the time measured by the timer 2a does not exceed the predetermined time (S11: No), or when the process of S12 is completed, other processes are performed (S13), and the process returns to S1. As other processing in S13, there is a setting processing for detecting the operation state of the operation element 5 and setting a parameter value in accordance with the operation when the operation is performed.

  As described above based on the first embodiment, the pad 1 and the pad 2 transmit and receive a signal including information indicating the strength of the hit when the hit is detected wirelessly. Therefore, it is possible to determine whether the sensor has detected a vibration or whether its own hitting surface has been struck by the propagation of the vibration generated by being struck by another pad 1.

  In the first embodiment, the plurality of pads 1 and the sound source device 30 communicate with each other by wireless communication. However, the pads 1 and the sound source device 30 may communicate with each other not by wireless but by wire. In the second embodiment, as an example of performing wired communication, each pad 21 includes an RS-485 driver instead of the wireless transmission / reception circuit 5, and the RS-485 drivers are connected to each other by a bus to communicate with each other. Do.

  FIG. 3 is a block diagram showing an electrical configuration of the pads 21 and 22 and the sound source device 41 in the second embodiment. In addition, about the structure same as 1st Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  As shown in FIG. 3, the sound source device 41 is connected to the CPU 33 and the RS-485 driver 42 via a bus. The pads 21 and 22 are connected to the CPU 2 and the RS-485 driver 16 via a bus. The RS-485 driver 42 of the tone generator 41 and the RS-485 driver 16 of each pad are connected to each other by an RS-485 bus 50. Even in the case of wired communication, the communication method is the same as in wireless communication, such as FDMA, TDMA, or CDMA, and a control signal such as a sound generation instruction signal is sent to the sound source device 41 and the pad 21. Or it is transmitted and received between a plurality of pads. In RS-485 communication, since a bus connection is used, an arbitrary number of pads can be connected without adding connectors.

  The present invention has been described above based on the embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications and changes can be easily made without departing from the spirit of the present invention. Can be inferred.

  For example, in the above-described embodiment, when a sound generation instruction signal transmitted by another pad is received, it corresponds to the type of percussion instrument assigned to the other pad based on the note-on velocity value included in the sound generation instruction signal. Although the impact strength applied to the other pads is acquired with reference to the velocity curve, information indicating the impact strength may be directly transmitted.

  Further, by comparing the vibration level detected by the piezo sensor 11 with a signal indicating the striking strength included in the sound generation instruction signal received from another pad, it is determined whether or not the hitting surface is hit. However, if the vibration level detected by the piezo sensor 11 is larger than a predetermined value (a value larger than the threshold value), it is not necessary to compare it with the impact strength included in the received sound generation instruction signal. May be determined to have been hit.

  In the above-described embodiment, the vibration level detected by the piezo sensor 11 is converted into a striking intensity and transmitted as a sound generation instruction signal. However, the vibration intensity detected by the piezo sensor 11 is separated from the sound generation instruction signal. The other pad 1 may receive the signal indicating the vibration intensity and determine whether or not its own hitting surface has been hit.

  In the above embodiment, the power supplied to the pad 1 is not described. However, a battery may be used, and the sound source device 30 and each pad 1 are connected by wire (wired) and supplied by the wiring. You may make it do.

  In the second embodiment, the plurality of pads 1 and the sound source device 30 are connected and communicated with each other by RS-485, which is one of wired communication methods. Instead of the 485 standard, a CAN (Controller Area Network) or the like may be used.

It is a block diagram which shows the electrical structure of the pad and sound source device of 1st Embodiment in this invention. It is a flowchart which shows the main process performed in a pad. It is a block diagram which shows the electrical structure of the pad and sound source device of 2nd Embodiment. It is an external appearance front view of the drum system for demonstrating the prior art. It is a block diagram which shows the electric constitution of the drum system which shows a prior art.

Explanation of symbols

1 Pad (Blow detection device)
2 CPU
3 ROM
3a Velocity curve (conversion table)
6 Wireless transceiver circuit (an example of input means and an example of wireless communication means)
11 Piezo sensor (example of sensor)
30 Sound source device S5 Impact determination means (part of vibration determination means)
S6 Strength information acquisition means S7 Output means

Claims (5)

In a hit detection device comprising a hitting surface, a sensor for detecting the vibration of the hitting surface, and an output means for outputting a sound generation instruction signal instructing the generation of a musical tone to the sound source device according to the vibration detected by the sensor ,
Input means for inputting a sound generation instruction signal output by another hit detection device;
Comparing the vibration detected by the sensor with the sound generation instruction signal input to the input means, and comprising a hit determination means for determining whether the hit surface has been hit,
The hit detection device, wherein the output means outputs a sound generation instruction signal when it is determined by the hit determination means that the hitting surface has been hit. The sound generation instruction signal includes intensity information indicating a vibration level,
The hit determination means performs the determination by comparing a vibration level detected by the sensor with a vibration level indicated by intensity information included in a sound generation instruction signal input to the input means. The hit detection device according to claim 1. When the sound generation instruction signal is input to the input means, the time measuring means for starting time measurement is provided,
3. The hit detection according to claim 1, wherein the hit determining means determines whether the hit face has been hit when the time counted by the timing means is within a predetermined time. apparatus. Wireless communication means for transmitting and receiving sound generation instruction signals wirelessly,
The input means inputs a sound generation instruction signal from another hit detection device by the wireless communication means, and the output means outputs a sound generation instruction signal by the wireless communication means. The hit detection device according to any one of the above. Conversion table storage means for storing a conversion table for converting the vibration level into intensity information;
Intensity information acquisition means for acquiring intensity information corresponding to the level of vibration detected by the sensor by referring to a conversion table stored in the conversion table storage means,
The impact detection device according to claim 1, wherein the output unit outputs a sound generation instruction signal including the intensity information acquired by the intensity information acquisition unit.

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