JP3580738B2 - Echo canceller controller - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an echo canceller control device for controlling an echo canceller for canceling an echo from a communication line in a system for performing voice communication.
[0002]
[Prior art]
FIG. 3 is a diagram for explaining a place where an echo is generated in a communication line.
[0003]
In FIG. 3, reference numeral 1 denotes a main unit for controlling a telephone call, reference numeral 2 denotes a telephone, and reference numeral 3 denotes a reflector such as a wall or a pillar. Reference numeral 11 denotes an echo canceller (echo canceller) of the main unit 1, 12 denotes a 2W / 4W conversion transformer unit (two-wire / four-wire conversion hybrid circuit) of the main unit 1, 13 denotes a 2W / 4W conversion transformer unit of the telephone 2, Reference numeral 14 denotes a handset.
[0004]
The 2W / 4W conversion transformer units 12 and 13 are used as an interface for conversion from 2-wire (2W) to 4-wire (4W) or conversion from 4-wire to 2-wire. In the 2W portion, a bidirectional audio signal flows, which is separated into a transmission audio signal and a reception audio signal. Also, due to the structure, a part of the transmission signal from the 4W side returns to the reception side. This is a hybrid echo caused by impedance mismatch.
[0005]
At the handset 14 of the telephone 2, part of the transmitted voice returns to the received voice side via the internal cavity and the housing, and becomes an acoustic echo.
[0006]
On the reflector 3 such as a wall or a pillar, the sound emitted from the receiver is reflected and enters the transmitter, and becomes an acoustic echo. This phenomenon occurs remarkably when the volume of sound is increased from a speaker in a hands-free telephone device and the emitted sound is picked up by a highly sensitive microphone.
[0007]
In order to remove such echoes and improve speech quality, an echo canceller including an adaptive filter and a subtractor is often used. An echo canceller is a device that internally has an estimated value of an impulse response of a reverberation path, estimates an echo by a convolution operation with a received signal, generates a pseudo echo, and cancels the echo by subtracting the pseudo echo from the transmitted signal. . Since the impulse response of the echo path changes with time, an adaptive echo canceller that adaptively estimates the impulse response is usually used.
[0008]
The echo canceller 11 has various functions so that it can always operate in an optimum state in addition to simply canceling the echo. For example, in an echo canceller having a learning function, a function parameter is automatically changed, and an adaptive operation is performed so that a value most suitable for a current voice path is obtained. Immediately after power-on and immediately after reset, each parameter has a default value. This default value is set, for example, to an intermediate value in a variable range so that an optimum state can be reached in a short time for any line state.
[0009]
However, if a new call is made after the call is terminated, the previous learning effect remains. There is a disadvantage that a lot of time is spent for the state to stabilize without matching the state. For example, assuming that the variable range of the parameter is 1 to 10 and that the parameter starts from 5 which is an intermediate value after resetting, normally “4” or “5” regardless of whether the parameter goes to 1 or 10 Reach the change. However, if the previous state is “1” due to the previous learning effect, a change time of “9” is required if the current state should be “10”. In addition to the time required for the state to stabilize, the sound signal is basically a continuous change. Therefore, there is an extreme time change such as the change time from the previous state “1” to the current state “10”. In some cases, the change of “9” is excluded from the parameters as an improbable signal, which may hinder the parameter adaptive operation.
[0010]
To solve the above problem, resetting the echo canceller by monitoring the communication state as shown in FIG. 4 has been performed.
[0011]
FIG. 4 is a block diagram showing the configuration of a conventional echo canceller control device.
[0012]
In FIG. 4, reference numeral 20 denotes an echo canceller control device for controlling an echo canceller for canceling echo from a telephone line, reference numeral 21 denotes an echo canceller, reference numeral 22 denotes a communication state monitoring unit, and reference numeral 23 denotes an echo canceller reset control unit. .
[0013]
Further, the communication state monitoring unit 22 receives call control information (hereinafter referred to as call information) from a main unit that performs call control (PBX (Private Branch Exchange), a device such as a telephone or an adapter that performs call control). Will be entered.
[0014]
In the above configuration, based on the call state managed by the main unit, the communication state monitoring unit 22 receives the information when a new call is started, and notifies the echo canceller reset control unit 23 of the information. The echo canceller reset control unit 23 resets the echo canceller 21 based on the call information from the communication state monitoring unit 22. By resetting, the various coefficients return to the initial values, and the convergence time (following time until the various coefficients enter the adaptive state) is reduced.
[0015]
[Problems to be solved by the invention]
However, in such a conventional echo canceller control device, a phenomenon occurs in which the above-described problem cannot be solved depending on the connection form of the line.
[0016]
FIG. 5 is a diagram showing a connection path from an apparatus equipped with an echo canceller to a terminal performing a call, and FIGS. 5 (a) to (g) show connection patterns 1 to 7. Here, the present apparatus is an apparatus provided with an echo canceller, such as the control device 20 in FIG. 4 (or the main device 1 in FIG. 3). The public network is actually an exchange of public network equipment. Also, the telephone is the terminal. The connection indicated by the hatched arrow in FIG. 5 has a two-wire / four-wire conversion, which may cause an echo. The connection portion indicated by an unhatched arrow in FIG. 5 does not generate an echo because it is connected in four lines.
[0017]
As for the connection patterns 1, 2, and 4, the telephone response can be detected by the present apparatus, so that the communication state can be monitored by detecting the telephone response, and the communication path is determined from this. Therefore, the above-described problem can be solved by resetting the echo canceller 21 by the echo canceller reset control unit 23 when a new call is started.
[0018]
However, regarding connection patterns 3, 5, 6, and 7, signals are output from the PBX or public network in the middle of the device and the telephone, and a communication path is once formed from the device to the corresponding answering device. Then, the communication path is changed to the telephone. In this case, the present apparatus can detect only the first response, so the only way to reset the echo canceller at that time is to do so. For this reason, the above-described problem has occurred at the time of a subsequent call path change.
[0019]
The present invention provides an echo canceller control device that can detect a change in a communication path and generate a reset signal in accordance with the change in the communication path, and can realize a stable echo cancellation state without being affected by a network connection configuration. The purpose is to provide.
[0020]
[Means for Solving the Problems]
The control device of the echo canceller according to the present invention includes an echo canceller for canceling an echo and a communication state for monitoring that a new call has been started based on a call state managed by a device that performs call control. Monitoring means, reset signal generating means for generating a reset signal for resetting the echo canceller based on information from the communication state monitoring means, Frequency monitoring means for monitoring a signal frequency of a line and generating frequency information; control means for controlling an echo canceller based on a reset signal from the reset signal generating means or information from the frequency monitoring means; Level monitoring means for monitoring the level and generating level information, wherein the control means controls the echo canceller when the frequency fluctuates more than a predetermined fluctuation width and the signal level thereafter remains substantially constant for a predetermined period. Perform a reset It is characterized by the following.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0026]
FIG. 1 is a block diagram showing a configuration of a control device of an echo canceller according to an embodiment of the present invention. In the description of the present embodiment, the same components as those in FIG. 4 are denoted by the same reference numerals.
[0027]
In FIG. 1, reference numeral 30 denotes a control device of an echo canceller for controlling an echo canceller for canceling echo of a communication line. The control device 30 of the echo canceller includes an echo canceller 21, a communication state monitoring unit 22 (communication state monitoring unit). ), An echo canceller reset control unit 23 (reset signal generation unit), a reset information integration control unit 31 (control unit), a level monitoring unit 32 (level monitoring unit), and a frequency monitoring unit 33 (frequency monitoring unit). . Reference numeral 34 denotes a communication line.
[0028]
The echo canceller 21 is a device that internally has an estimated value of the impulse response of the echo path, estimates the echo by convolution with the received signal, and cancels the echo by subtracting it from the transmission signal. This is realized by using a DSP (digital signal processor). The DSP has an arithmetic unit mainly having a multiplication function, and performs signal processing by controlling the arithmetic function and data transfer by firmware.
[0029]
The communication state monitoring unit 22 receives call information from a main unit (not shown) such as a PBX, a telephone, an adapter, or the like that performs call control, and performs a new call based on the call state managed by the main unit. Is started and the information is notified to the echo canceller reset control unit 23.
[0030]
The echo canceller reset control unit 23 creates a reset signal suitable for the echo canceller 21 based on information from the communication state monitoring unit 22.
[0031]
The reset information integrated control unit 31 is constituted by a microcomputer or the like, and comprehensively determines based on information from the level monitoring unit 32 and the frequency monitoring unit 33 and a reset signal from the echo canceller reset control unit 23, and determines an optimal timing. To generate a reset signal and send it to the echo canceller 21.
[0032]
The level monitoring unit 32 monitors the signal level from the line, generates level (LV) information, and outputs it to the reset information integrated control unit 31.
[0033]
The frequency monitoring unit 33 monitors the signal frequency from the line, generates frequency (FQ) information, and outputs it to the reset information integrated control unit 31.
[0034]
Hereinafter, the operation of the echo canceller control device 30 configured as described above will be described.
[0035]
First, the characteristics of each signal (call control tone, PB (push button) signal tone during a call, voice signal) will be briefly described in relation to the level and frequency.
[0036]
The call control tone is a signal tone emitted for controlling / displaying a call state, and includes a dial tone (DT) indicating a dial input enabled state, a ring back tone (RBT: ringing tone) indicating a calling state of the other party, and a called party. There is a busy tone (BT) indicating a busy state. An interrupt sound indicating an interrupt (call waiting, transfer phone, etc.) during a call is output at a predetermined frequency at a predetermined frequency.
[0037]
The PB signal tone during a call is a signal transmitted to input number information (FAX service, voice mail service, etc.) from the state during a call. The PB signal is represented by dial numbers in a combination of high and low two frequencies from four kinds of high frequency groups (1209, 1336, 1447, 1633 Hz) and four kinds of low frequency groups (697, 770, 852, 941 Hz). I have. The frequency is changed by the combination, but the level is constant.
[0038]
The voice signal is obtained by converting the voice of the caller into a signal. The frequency changes continuously, and the level also changes continuously. When the call path is changed, the level may fluctuate due to a difference in signal loss between the paths.
[0039]
Since a normal audio signal is a continuous change, its level and frequency do not change significantly. If the level or the frequency changes significantly, it may be determined that the connection path has changed. This will be described by taking the case of the connection pattern 3 of the communication path in FIG. 5C as an example.
[0040]
In FIG. 5C, when a telephone is called from the apparatus, the PBX first responds to the apparatus, and a communication path is formed between the apparatus and the PBX. At this time, an RBT (ringing tone) calling the extension terminal is sent from the PBX to the apparatus. In the conventional example, the reset is performed assuming that the communication channel is determined at this time. Next, when the telephone answers, the PBX changes "the communication path between the PBX internal tone device and this device" to "the communication channel between the telephone and this device". A normal RBT signal is an intermittent tone having a frequency of “400 Hz + 20 Hz modulation” and a level of “−5 dBm to −10 dBm”. −−25 dBm ”(there is a difference between speakers). Therefore, if a change in frequency or level is detected, it is possible to determine a change in the communication channel.
[0041]
A specific operation of the echo canceller control device 30 will be described in accordance with the above basic concept. The operation will be described with reference to the connection pattern 7 shown in FIG.
[0042]
In FIG. 5G, reference numeral 41 denotes the apparatus, reference numeral 42 denotes a PBX, reference numeral 43 denotes a public network, reference numeral 44 denotes a PBX, and reference numeral 45 denotes a telephone. The present device 41 is a device that includes the echo canceller control device 30 (FIG. 1) according to the present embodiment and performs call control such as a PBX, a telephone, and an adapter.
(1) First, a call is made from the device 41 to the telephone 45.
(2) In response, the PBX 42 responds, and a communication path between the device 41 and the PBX 42 is formed. The communication state monitoring unit 22 receives call start information (call information) based on the call state managed by the main unit, and sends the call information to the echo canceller reset control unit 23. The echo canceller reset control unit 23 creates a reset signal suitable for the echo canceller 21 based on the received call information. The generated reset signal is sent to the echo canceller 21 via the reset information integration control unit 31, and the echo canceller is reset (initialized). The operation up to this point is the same as that of the conventional example.
(3) Next, a DT (dial tone) or guidance prompting the destination dial input from the PBX 42 is transmitted to the apparatus 41. In the present device 41, the tone or the guidance signal is received from the initial silence state. Therefore, the reset information integration control unit 31 uses the FQ fluctuation information from the frequency monitoring unit 33 and the LV fluctuation information from the level monitoring unit 32 to perform the reset. It is determined whether or not the communication path has been changed, and when it is determined that the communication path has been changed, a reset signal is created and transmitted to the echo canceller 21. The echo canceller 21 is reset by the reset signal. The details of the integrated control by the reset information integrated control unit 31 will be described later.
(4) After sending the destination information from the device 41, the PBX 42 calls the PBX 44 via the public network 43. At this time, the PBX 42 changes “the communication path between the present apparatus 41 and the PBX 42” to “the communication path between the present apparatus 41 and the public network 43”. Then, an RBT (ringing tone) is sent from the exchange of the public network 43 to the apparatus 41.
[0043]
In the apparatus 41, the received signal changes as "DT → silence → RBT", and the level monitor 32 and the frequency monitor 33 detect this change, respectively, and the same process as the process (3) is performed. Done.
(5) In the case where the PBX 44 and the telephone 45 are registered in a DIL (direct inline: a service that can call an extension of the PBX directly from the public network), the telephone 45 responds to the call state between the present apparatus 41 and the telephone 45. become. At this time, the communication path is changed from “the communication path between the present apparatus 41 and the public network 43” to “the communication path between the present apparatus 41 and the telephone 45”. In the device 41, the received signal changes from “RBT to audio signal”, and the change is detected by the level monitor 32 and the frequency monitor 33, respectively, and the same process as the process (3) is performed. Be done.
(6) In the case where the PBX 44 and the telephone 45 are registered as a DID (direct indial: a service that can call an extension of the PBX directly from the public network), when the PBX 44 responds, a temporary call state is established and the communication path is changed. The "communication path between the present apparatus 41 and the public network 43" is changed to the "communication path between the present apparatus 41 and the PBX 44".
[0044]
From the PBX 44, a DT (dial tone) or guidance for prompting the user to dial the extension number of the destination is sent to the apparatus 41. The DID registration is the same as the DIL registration in (5) above in that the extension of the PBX can be called directly from the public network, except that the PBX 44 responds with DT or guidance and enters a temporary call state.
[0045]
In the apparatus 41, the received signal changes from "RBT to DT / guidance", and this change is detected by the level monitor 32 and the frequency monitor 33, respectively, and the same process as the process (3) is performed. Done.
(7) Thereafter, the telephone 45 responds to the communication between the device 41 and the telephone 45. At this time, the communication path is changed from “the communication path between the present apparatus 41 and the PBX 44” to “the communication path between the present apparatus 41 and the telephone 45”.
[0046]
In the device 41, the received signal changes from “RBT to audio signal”, and the change is detected by the level monitor 32 and the frequency monitor 33, respectively, and the same process as the process (3) is performed. Be done.
[0047]
FIG. 2 is a flowchart showing the integrated control of the reset information integrated control unit 31. In the present embodiment, the reset information integration control unit 31 is configured by a programmed computer that executes the operation illustrated in FIG. 2 at predetermined time intervals, but may be configured by a logic circuit instead.
[0048]
First, in step ST1, it is determined whether or not a predetermined time has elapsed since the initial reset or the reset according to the present flow. If the predetermined time has elapsed, it is determined in step ST2 whether or not the predetermined time has elapsed since the start of the call. As described above, immediately after resetting or immediately after a call starts, the following operations are not started until the above-mentioned predetermined time has elapsed since the state is unstable.
[0049]
Here, the start of the call is determined based on the call start information (call information) from the communication state monitoring unit 22. After the start of the call, the communication state is established, and thereafter, even if there is call end information (end of call), the state of the call is maintained until reset. When a call is in progress, the level monitor 32 detects a change in the signal level of the line, and the frequency monitor 33 detects the signal frequency of the line.
[0050]
In step ST3, it is determined whether or not the signal level fluctuates by a predetermined fluctuation width or more based on the LV fluctuation information from the level monitoring unit 32 and the state continues for a predetermined time or more. If the signal level continues for a predetermined time or more, it is determined that there is a significant change in the communication state, such as a change in the communication path, and it is necessary to immediately reset the communication state. Send out. The echo canceller 21 is reset by the reset signal.
[0051]
If the signal level does not continue for a predetermined time in step ST3, the frequency fluctuates by a predetermined fluctuation width based on the FQ fluctuation information from the frequency monitoring unit 33 in step ST5, and the state changes for a predetermined time. It is determined whether or not the above has been continued. If the frequency fluctuation does not continue for a predetermined time or longer, it is determined that resetting is not necessary, and this flow is ended to continue the busy state.
[0052]
On the other hand, if the frequency fluctuation has continued for a predetermined time or more in step ST5, the process proceeds to step ST6, and in step ST6, it is determined whether or not there is a level fluctuation for a certain period based on the LV fluctuation information from the level monitoring unit 32. I do. If there is no level fluctuation for a certain period, it is determined that the condition is such that the echo canceller 21 can be reset, and the reset is performed in step ST4. If there is a change in the level, it is determined that there is no condition for resetting, and this flow is terminated.
[0053]
That is, when the fluctuation width of the frequency is equal to or more than the predetermined value, it is confirmed that there is no level fluctuation for a certain period in step ST6, and then reset when there is no level fluctuation for a certain period. This is because when the frequency fluctuates and the level is fixed for a certain period of time, for example, when a call control tone is included in the voice signal, the continuity of the learning effect cannot be expected in this case, so that promptly Perform a reset to start a new learning. On the other hand, even if there is the above-mentioned fluctuation in the frequency, the reset is not performed by itself, but is performed only when there is no level fluctuation for a certain period. This is based on the fact that it is the human voice that fluctuates in frequency and level, so that if both such frequency and level fluctuate (for example, if the tone of the speaker changes), Saves the learning result without resetting and continues learning.
[0054]
As described above, the control device 30 for the echo canceller according to the embodiment starts a new call based on the echo canceller 21 for canceling the echo and the call state managed by the device that controls the call. A communication state monitoring unit 22 for monitoring the occurrence of the call, an echo canceller reset control unit 23 for resetting the echo canceller based on the call information, a level monitoring unit 32 for monitoring the signal level of the communication line and generating the level information. A frequency monitoring unit 33 that monitors the signal frequency of the communication line and generates frequency information; and a total based on information from the level monitoring unit 32 and the frequency monitoring unit 33 and a reset signal from the echo canceller reset control unit 23. A reset information integrated control unit 31 for determining and generating a reset signal at an optimal timing to control the echo canceller 21 Since it is configured Te, only call information from the main device can detect the change in the speech path which did not know, it is possible to prevent the delay of the echo cancellation state stabilization after the change in the speech path.
[0055]
Specifically, the following effects (1) to (6) can be obtained.
(1) It is possible to detect a change in the communication path that could not be determined by the call control circuit of the main unit.
(2) It is possible to generate an echo canceller reset signal corresponding to a change in a communication path.
(3) A stable echo cancellation state can be provided without being affected by the connection configuration of the network.
(4) When an unexpected state change occurs, such as when the handset falls to the floor and an excessively loud signal enters, the change can be detected and the echo canceller can be reset. That is, the echo canceller can be reset immediately upon detecting a sudden state change, so that the effect can be minimized.
(5) Even in the case where the present apparatus cannot originally understand the state of the communication path configuration, such as the transfer operation of the other party in the call state, the level / frequency change during transmission is detected to detect the communication path. The situation can be detected.
(6) Since there is no restriction on the network configuration such as the communication path configuration and connection pattern or the place of use, the system design can be performed more easily.
[0056]
Here, in the present embodiment, a reset signal is generated at an optimum timing based on information from the level monitoring unit 32 and the frequency monitoring unit 33 to control the echo canceller 21. A configuration in which only one of the level monitoring unit 32 and the frequency monitoring unit 33 is provided may be employed. As described above, if only one of them is provided, the cost can be reduced.
[0057]
There is a difference between the method of monitoring the fluctuation of the signal level of the line and the method of monitoring the fluctuation of the signal frequency of the line in the content of the detected call state. When speaking normally, there is no difference between the two because the level and frequency also change continuously.
[0058]
However, when the communication route is changed, for example, when the route is switched from the operator to the transfer destination, the frequency of the sound does not change but the signal level may greatly change. The level monitoring unit 32 that monitors the signal level of the line can appropriately detect such a change in the audio signal.
[0059]
On the other hand, when a sound of the same level and a different frequency interrupts during a call, for example, when an extension ringing tone is interrupted, the frequency does not change but the frequency changes to another frequency. The frequency monitoring unit 33 that monitors the signal frequency of the line can detect such a change in the frequency.
[0060]
In the present embodiment, since both the level monitoring unit 32 and the frequency monitoring unit 33 are installed, it is possible to appropriately detect a change in the call state and reset in any case.
[0061]
Further, in the present embodiment, the level fluctuation and the frequency fluctuation processing are not performed simply by detecting the level fluctuation and the frequency fluctuation, but by performing the integrated control of the reset information integrated control unit 31 as described in FIG. The optimal reset can be performed by combining. For example, in the example of FIG. 2, when the fluctuation range of the level is equal to or more than a predetermined value, the reset is immediately performed on the assumption that there is a significant change in the communication state, but the level does not fluctuate for a certain period even if the frequency fluctuates. Make sure to reset for the first time. This makes it possible to perform reset at an appropriate timing while utilizing the learning function as much as possible. Note that the integrated control in FIG. 2 is an example, and any control method may be used.
[0062]
Further, the control device of the echo canceller according to the present embodiment can be applied to, for example, a hands-free telephone device, but is not limited to this, and is applicable to all devices as long as the control device is an echo canceller. is there.
[0063]
Further, in the present embodiment, when the level / frequency from the line exceeds a predetermined fluctuation range and the state continues for a predetermined time or more, the level / frequency information is generated. , The set value of the fluctuation range may be changed, or the duration may be made variable.
[0064]
Further, the types, numbers, connection methods, and the like of the respective circuit units and the like constituting the control device are not limited to the above-described embodiments.
[0065]
【The invention's effect】
In the echo canceller control device according to the present invention, An echo canceller for canceling the echo, a communication state monitoring means for monitoring the start of a new call based on a call state managed by a device for controlling the call, and information from the communication state monitoring means. Reset signal generating means for generating a reset signal for resetting the echo canceller based on: a frequency monitoring means for monitoring a signal frequency of a line to generate frequency information; and a reset signal or frequency from the reset signal generating means. The control unit controls the echo canceller based on the information from the monitoring unit, and the level monitoring unit monitors the signal level of the line and generates the level information. Changes in call status by detecting changes in call status Can be generated, and a stable echo canceling state can be realized without being affected by the network connection configuration.
[0066]
In the echo canceller control device according to the present invention, a frequency monitoring unit that monitors a signal frequency of a line and generates frequency information, and an echo canceller based on a reset signal from a reset signal generating unit or information from the frequency monitoring unit. Control means for controlling, when there is an interruption during a call, a change in the call state can be detected and a reset signal adapted to the change in the call state can be generated. A stable echo cancellation state can be realized without being affected.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a control device of an echo canceller according to an embodiment to which the present invention is applied.
FIG. 2 is a flowchart showing integrated control of a reset information integrated control unit of the echo canceller control device.
FIG. 3 is a diagram for explaining a place where an echo is generated in a conventional communication line.
FIG. 4 is a block diagram showing the configuration of a conventional echo canceller control device.
FIG. 5 is a diagram showing a conventional communication path connection pattern.
[Explanation of symbols]
21 echo canceller, 22 communication status monitor (communication status monitor), 23 echo canceller reset controller (reset signal generator), 30 echo canceller controller, 31 reset information integrated controller (controller), 32 level monitor Section (level monitoring means), 33 frequency monitoring section (frequency monitoring means), 34 telephone line

Claims (1)

An echo canceller for canceling the echo,
Communication state monitoring means for monitoring that a new call has started, based on a call state managed by a device that performs call control;
Reset signal generating means for generating a reset signal for resetting the echo canceller based on information from the communication state monitoring means,
Frequency monitoring means for monitoring the signal frequency of the line and generating frequency information;
Control means for controlling an echo canceller based on a reset signal from the reset signal generation means or information from the frequency monitoring means,
Level monitoring means for monitoring the signal level of the line and generating level information;
With
The echo control unit resets the echo canceller when the frequency fluctuates by a predetermined fluctuation width or more and thereafter, the signal level keeps a substantially constant value for a predetermined period. Canceller control device.

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