CN105934931B - A kind of terminal installation - Google Patents

Abstract

An embodiment of the present invention provides a terminal device. When the control function corresponding to at least one of the at least two buttons of an earphone fails, the terminal device obtains at least two signals generated by the earphone circuit when the user operates the at least two buttons. The electrical signals are obtained, and a recognition threshold is obtained according to the obtained at least two electrical signals, so that the control functions corresponding to the at least two buttons are recognized based on the recognition threshold. In this way, even if the headset is used for a period of time, hardware aging occurs, because the identification threshold is set based on the electrical signal of the key after the hardware is aging, so that the terminal device can identify the key pressed by the user.

Description

a terminal device

technical field

The present invention relates to a terminal device, in particular to a terminal device for identifying control functions corresponding to keys of an earphone.

Background technique

Taking a mobile phone as an example, the terminal device often uses an earphone suitable for connecting to the terminal device, so that the loudspeaker that is placed outside may not affect others.

The above-mentioned earphone is an abbreviation of earphone receiver, which refers to a small receiver that can be worn on the ear. The above-mentioned earphone is inserted into the ear after the small speaker is fixed by a specific casing, and the connecting terminal connected with the small speaker is inserted into the jack of the terminal device, so that the sound wave output by the small speaker propagates to the user's ear.

The above-mentioned earphones are usually also provided with buttons on the connection line between the connection terminal and the small speaker, which are used to partially control the terminal device. Taking the headset as an example, the commonly used buttons may include three buttons, a volume up button, a volume down button, and a confirmation button. The volume up or down here is an example of a control function, which can be other control functions or Multiplexed keys have other control functions.

However, after the same earphone is used for a period of time, the hardware circuit will age, so that the terminal device cannot recognize or incorrectly recognize the keys operated by the user.

Although the above description is based on wired earphones, the earphones may also be wireless earphones, such as Bluetooth earphones. Although Bluetooth headsets do not need to be wired, Bluetooth headsets usually include buttons, and there are similar problems.

SUMMARY OF THE INVENTION

An embodiment of the present invention provides a terminal device for identifying a control function corresponding to a button of an earphone.

In a first aspect, an embodiment of the present invention provides a terminal device, where the terminal device includes:

input and output units;

The earphone interface is used for connecting with the earphone; the earphone includes at least two buttons, and the at least two buttons respectively correspond to a control function; operate to generate electrical signals;

The control unit is configured to acquire at least two electrical signals generated by the earphone circuit when the user operates the at least two buttons when the control function corresponding to at least one of the at least two buttons fails, and according to the The acquired at least two electrical signals obtain a recognition threshold, and based on the recognition threshold, the control functions corresponding to the at least two keys are recognized.

In a first possible implementation manner of the first aspect, the at least two buttons include a first button and a second button, and correspondingly, the acquisition of the user operating the at least two buttons is generated by the earphone circuit. the at least two electrical signals include a first electrical signal and a second electrical signal;

The control unit is configured to: obtain the identification threshold according to a preset rule based on the first electrical signal and the second electrical signal.

In combination with the first possible implementation manner of the first aspect, in a second possible implementation manner, the threshold is a single value; the first electrical signal is represented by a first value, and the second electrical signal is represented by a second value ;

Then the control unit is specifically configured to: set a certain value between the first value and the second value as the identification threshold.

With reference to the second possible implementation manner of the first aspect, in a third possible implementation manner, the control unit is further configured to:

receiving a third electrical signal generated by the earphone circuit when the user operates the first button or the second button;

comparing the magnitude relationship between the third electrical signal and the identification threshold;

According to the comparison result, the control function corresponding to the third electrical signal is identified according to a preset rule.

In combination with the third possible implementation manner of the first aspect, in the fourth possible implementation manner, the control unit is specifically used for:

When the third electrical signal is less than or equal to the identification threshold, it is identified as the control function corresponding to the first button;

When the third electrical signal is greater than the identification threshold, it is identified as the control function corresponding to the second key;

With reference to the first possible implementation manner of the first aspect, in a fifth possible implementation manner, the identification threshold is a numerical value range, including a lower limit value and an upper limit value; the first electrical signal is characterized as a first numerical value , the second electrical signal is characterized as a second value,

Then the control unit is specifically configured to: obtain the lower limit value and the upper limit value of the first identification threshold based on the first numerical value and the first threshold factor, and obtain the second identification threshold based on the second numerical value and the second threshold factor lower and upper limit values.

With reference to the fifth possible implementation manner of the first aspect, in the sixth possible implementation manner, the control unit is further configured to:

receiving a fourth electrical signal generated by the earphone circuit when the user operates the first button or the second button;

comparing the magnitude relationship between the fourth electrical signal and the first identification threshold and the second identification threshold;

According to the comparison result, the control function corresponding to the fourth electrical signal is identified according to a preset rule.

With reference to the fifth possible implementation manner of the first aspect, in the seventh possible implementation manner, the control unit is specifically used for:

When the fourth electrical signal is greater than or equal to the lower limit of the first identification threshold and less than or equal to the upper limit of the first identification threshold, it is identified as a control function corresponding to the first key;

When the fourth electrical signal is greater than or equal to the lower limit of the second identification threshold and less than or equal to the upper limit of the second identification threshold, it is identified as a control function corresponding to the second key;

In a second aspect, an embodiment of the present invention provides a terminal device, where the terminal device includes:

input and output units;

The earphone interface is used for connecting with the earphone; the earphone includes at least two buttons, and the at least two buttons respectively correspond to a control function; operate to generate electrical signals;

The control unit is configured to acquire at least one electrical signal generated by the earphone circuit when the user operates the at least one key that fails when the control function corresponding to at least one of the at least two keys fails, and according to The obtained at least one electrical signal obtains a recognition threshold, and according to the recognition threshold, the control functions corresponding to the at least two buttons are recognized;

Wherein, the identification threshold is a numerical range, including a lower limit value and an upper limit value.

In a first possible implementation manner of the second aspect, the at least two keys include a first key and a second key, and the at least one key that fails is the first key, and accordingly the acquiring the user operation The at least one electrical signal generated by the earphone circuit due to the disabled at least one button includes: obtaining a first electrical signal generated by the earphone when the user operates the disabled first button, and the first electrical signal is characterized as the first electrical signal. a value;

The control unit is configured to: obtain a lower limit value and an upper limit value of the identification threshold based on a first value represented by the first electrical signal and a first threshold factor.

In combination with the first possible implementation manner of the second aspect, in the second possible implementation manner, the control unit is further configured to:

receiving a fifth electrical signal generated by the earphone circuit when the user operates the first button or the second button;

comparing the magnitude relationship between the fifth electrical signal and the identification threshold;

According to the comparison result, the control function corresponding to the fifth electrical signal is identified according to a preset rule.

In combination with the second possible implementation manner of the second aspect, in the third possible implementation manner, the control unit is specifically used for:

When the fifth electrical signal is greater than or equal to the lower limit of the identification threshold and less than or equal to the upper limit of the identification threshold, it is identified as a control function corresponding to the first key.

In this embodiment of the present invention, when the control function corresponding to at least one of the at least two buttons of the earphone fails, the terminal device acquires at least two electrical signals generated by the earphone circuit when the user operates the at least two buttons, And a recognition threshold is obtained according to the obtained at least two electrical signals, so that control functions corresponding to the at least two keys are recognized based on the recognition threshold. In this way, even if the headset is used for a period of time, hardware aging occurs, because the recognition threshold is set based on the electrical signal of the key after the hardware is aging, so that the terminal device can recognize the key pressed by the user.

Description of drawings

In order to illustrate the technical solutions in the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings used in the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained from these drawings without creative effort.

FIG. 1 is a schematic diagram of a partial structure of a terminal device according to an embodiment of the present invention;

2 is a schematic diagram of an earphone circuit of an earphone according to an embodiment of the present invention;

3a and 3b are schematic diagrams of an identification method according to an embodiment of the present invention;

4a and 4b are schematic diagrams of another identification manner according to an embodiment of the present invention;

5 is a schematic diagram of a corrected identification method according to an embodiment of the present invention;

FIG. 6 is a schematic diagram of another identification manner after correction according to an embodiment of the present invention.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments These are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The terminal device in the embodiment of the present invention may include a mobile phone, a tablet computer, an mp3 player, a PDA (personal digital assistant, personal digital assistant), and the like.

1 , the terminal device 100 may include a control unit 110 , a memory 120 , an input unit 130 , an output unit 140 , an earphone interface 150 and other components. In addition, the earphone 151 is an accessory of the terminal device 100 connected to the earphone interface. Those skilled in the art can understand that the structure of the terminal device shown in FIG. 1 does not constitute a limitation on the terminal device, and may include more or less components than those shown in the figure, or combine some components, or arrange different components.

Each component of the terminal device 100 will be specifically introduced below with reference to FIG. 1 :

The control unit 110 is the control center of the terminal device 100 , and may be a processor chip or any unit or module having a control function. It uses various interfaces and lines to connect various parts of the entire terminal device. By running or executing software programs and/or modules stored in the memory 120 and calling data stored in the memory 120, various functions of the terminal device 100 are performed, thereby overall monitoring the terminal device.

Memory 120 may be used to store software programs and related data. The control unit 110 executes various functional applications and data processing of the terminal device 100 by executing software programs and data stored in the memory 120 .

The input unit 130 may be used to receive input numerical or character information, and generate key signal input related to user settings and function control of the terminal device 100 . Specifically, the input unit 130 may include, but is not limited to, one or more of a touch screen, a physical keyboard, function keys (such as volume control keys, switch keys, etc.), trackball, mouse, joystick, and the like.

The output unit 140 may include a display device or an audio playback device or the like. The display device may be used to display information input by the user or information provided to the user and various menus of the terminal device 100 . The display device may include a display screen. The audio playback device includes at least a speaker, an audio circuit, and the like. The audio circuit can transmit the received audio data converted signal to the speaker, and the speaker converts it into a sound signal and outputs it.

The earphone interface 150 is suitable for connecting with the earphone 151 . Since earphones can be at least divided into wired earphones and wireless earphones, the connection can be wired connection or wireless connection accordingly. The earphone interface itself may include all or part of a circuit, a jack, a wireless module, etc., which belongs to the prior art and will not be repeated here. The earphone 151 may be provided with buttons for partially controlling the terminal device 100 . Taking a mobile phone headset as an example, the commonly used buttons may include three buttons, a volume up button, a volume down button, and a confirmation button. The volume up or down here is only an example of the control function, and can be other control functions. , you can also reuse the above keys to have other control functions. The earphone 151 also includes an earphone circuit (described in detail below) for generating an electrical signal in response to a user's operation of a key. The electrical signal may be voltage, current, etc., preferably voltage.

Those skilled in the art can understand that the structure of the terminal device shown in FIG. 1 does not constitute a limitation on the terminal device. Those of ordinary skill in the art can make appropriate changes to the structure in FIG. 1 as required. For example, some components are deleted, some components are added, or some components in Figure 1 are replaced by other components. .

FIG. 2 shows a schematic diagram of the earphone circuit in the earphone, because the earphone circuit belongs to the prior art in the field, so it will not be described in detail here, and the following description is only for the convenience of understanding. In addition, FIG. 2 shows the structure of the earphone circuit of the existing wired earphone, but it is only used to understand the working principle and does not constitute any limitation.

As shown in Figure 2, SPK_L and SPK_R respectively represent left and right small speakers, one of the terminals L+ of the left speaker is electrically connected to the L terminal, one of the terminals R+ of the right speaker is electrically connected to the R terminal, the left speaker and the right speaker are electrically connected to the R terminal. The other terminals of the speakers are both connected to the G terminal (ground terminal).

There are three buttons, including the confirmation button SW1 (also known as the button Key_OK), the volume down button SW2 (also known as the button Key_V-), and the volume increase button SW3 (also known as the button Key_V+), which are respectively used for confirmation, Controls volume down and volume up. It can be understood that the number of buttons and control functions are not limited, for example, at least two buttons are sufficient.

There are three resistors R1, R2, R3 in the series/parallel connection of the three buttons, and each resistor is preset to a certain resistance value. Of course, the headphone circuit also includes other components, such as a capacitor C1, a microphone MIC, etc., which are not described in this embodiment of the present invention.

Referring to FIG. 2 , it can be seen that when the user operates different buttons, the earphone circuit is connected to different flow paths, and different electrical signals are generated at the M+ terminal due to different resistance values. For convenience, the description is made by taking the electrical signal as a voltage as an example.

The terminal device can collect the voltage V of the M+ terminal in the earphone circuit, and identify which key is the key according to the preset identification threshold and rules.

Currently, there are at least two identification methods based on different mechanisms.

The first way, as shown in Figure 3a, identifies the way in which the threshold is a single value.

For example, the terminal device presets two thresholds, each of which is a single value: threshold TH1, threshold TH2;

When V≤TH1, it is recognized that the key SW1 (Key_OK) is operated, and the corresponding confirmation function is triggered;

When V≥TH2, it is recognized that the key SW2 (Key_V-) is operated, and the corresponding volume reduction function is triggered;

When TH1<V<TH2, it is recognized that the key SW3 (Key_V+) is operated, and the corresponding volume increase function is triggered.

It is easy to understand that the above identification rules can be set as required.

However, if the hardware is aging, for example, the resistance value of the resistor in series with the button SW3 (Key_V+) changes, then it is possible that the user operates the button SW3 (Key_V+) as shown in Figure 3b, and the voltage value V+ at the M+ terminal exceeds TH2 (such as the dotted line). shown), according to the above rules, even if the user operates the key SW3 (Key_V+), the terminal device will recognize that the key SW2 (Key_V-) is operated. This is obviously inaccurate.

The second way, as shown in Figure 4a, identifies the way that the threshold is a range of values.

For example, the terminal device presets three thresholds, each of which is a value range, including upper and lower limits: threshold TH1 (lower limit A1, upper limit A2), threshold TH2 (lower limit B1, upper limit B2), threshold TH3 (lower limit C1, upper limit C2),

When A1≤V≤A2, it is recognized that the key SW1 (Key_OK) is operated, and the corresponding confirmation function is triggered;

When B1≤V≤B2, it is recognized that the key SW3 (Key_V+) is operated, and the corresponding volume increase function is triggered.

When C1≤V≤C2, it is recognized that the key SW2 (Key_V-) is operated, and the corresponding volume reduction function is triggered.

It is easy to understand that the above-mentioned identification rules can be set as required.

Similarly, if the hardware is aging, for example, the resistance value of the resistor in series with the button SW1 (Key_OK) has changed, then it is possible that the user operates the button SW1 (Key_OK), as shown in Figure 4b, the voltage value V at the M+ terminal _. If _k exceeds the upper limit value A1 of the threshold value TH1 (as shown by the dotted line), even if the user operates the key SW1 (Key_OK), the terminal device cannot recognize it.

The embodiments of the present invention are intended to solve the above problems. That is, when the control function corresponding to at least one button of the earphone fails, how to identify the control function of the button. The failure at least includes that when a user operates a certain key, the terminal device cannot identify its corresponding control function. The corresponding control function may be preset by the manufacturer, or may be set by the user.

The terminal device may provide a correction function, which can be activated by the user when at least one key fails. The embodiment of the present invention does not limit how to provide the correction function, and the user may be guided for the next operation in a voice manner, or in a graphical interface manner, or both, and so on. For the convenience of description, the following is introduced in the form of a graphical interface.

For the convenience of understanding, the embodiments of the present invention are respectively introduced according to two identification methods.

(1) Corresponding to the first method above:

When at least one key, such as key SW3 (Key_V+), fails, the user can activate the calibration function and open a graphical interface for calibration. Of course, the terminal device may also prompt the user for correction, for example, periodically and actively prompt the user.

The terminal device can guide the user through the graphical interface to operate the three buttons in sequence according to the control function, for example, corresponding to the confirmation function, prompting the user to operate the button SW1 (Key_OK), corresponding to the volume increase function, prompting the user to operate the button SW3 (Key_V+), corresponding to the volume decrease. Small function, prompting the user to operate SW2 (Key_V-). It will be understood that the order of operations is not intended to be limiting.

The control unit of the terminal device acquires the electrical signals, such as voltages, of the M+ terminal in the earphone circuit when the user operates the above-mentioned three buttons, which are assumed to be V1, V3, and V2 respectively.

Based on the above-mentioned voltages V1, V3, V2, the control unit obtains the identification thresholds TH1', TH2'. The control unit may set a rule to obtain the identification threshold. For example, a certain voltage value between V1 and V3 can be used as the first identification threshold TH1' to distinguish the keys SW1 (Key_OK) and SW3 (Key_V+), and a certain voltage value between V3 and V2 can be used as the difference between the keys SW3 (Key_V+) and SW3 (Key_V+). The second identification threshold TH2' of SW2 (Key_V-). Preferably, the average value of V1 and V3 can be taken as the first identification threshold TH1', and the average value of V3 and V2 can be taken as the second identification threshold TH2'.

Based on the identification threshold, the terminal device identifies the control functions of the three keys. After the calibration, if the user operates any button, the headphone circuit will generate a voltage value V', and the control unit will compare the relationship between the voltage value V' and the above identification threshold, and identify the control function corresponding to the case according to the preset rules . For example, if V'≤TH1', it is recognized that the key SW1 (Key_OK) is operated, if V'≥TH2', it is recognized that the key SW2 (Key_V-) is operated, if TH1'<V'<TH2', Then it is recognized that the key SW3 (Key_V+) is operated.

It is easy to understand that the number of buttons may be at least two, and the control functions corresponding to the buttons are not limited, but the principles are similar.

In this way, even if the headset is used for a period of time, hardware aging occurs, because the recognition threshold is set based on the electrical signal of the key after the hardware is aging, so that the terminal device can recognize the key pressed by the user.

In addition, the resistance values and/or working voltages of the earphone circuits of earphones of different manufacturers may be different, so when different earphones are used with the same mobile terminal, if the same recognition threshold is used, it will also cause the user to operate the buttons. , the terminal equipment cannot be identified or misidentified. The embodiment of the present invention can also solve this problem, because the terminal device can reset the recognition threshold according to each earphone, so as to recognize the buttons of different earphones.

(2) Corresponding to the above-mentioned second method, the places similar to those of the first method are not repeated here.

When at least one key, such as the key SW1 (Key_OK), fails, the user can activate the calibration function and open a graphical interface for calibration. Of course, the terminal device may also prompt the user for correction, for example, periodically and actively prompt the user.

The terminal device can guide the user to operate the three buttons in sequence according to the control function, for example, corresponding to the confirmation function, prompting the user to operate the button SW1 (Key_OK), corresponding to the volume increase function, prompting the user to operate the button SW3 (Key_V+), corresponding to the volume decrease function, Prompt the user to operate SW2 (Key_V-). It will be understood that the order of operations is not intended to be limiting.

The control unit of the terminal device acquires the electrical signals, such as voltages, of the M+ terminal in the earphone circuit when the user operates the above-mentioned three buttons, which are assumed to be V1, V3, and V2 respectively.

Based on the above-mentioned voltages V1, V3, V2, the control unit obtains the identification threshold. The control unit may preset a rule to obtain the identification threshold. For example, the identification threshold can be obtained according to the threshold factor, and the threshold factor is used as the upper limit and the lower limit for determining the identification threshold. For example, the first threshold factor is a1, a2, then V1-a1 is set as A1', and V1+a2 is set as A2', so as to obtain the lower and upper limits A1' and A2' of the first identification threshold; the second threshold factor is b1, b2, V3-b1 is set as B1', and V1+b2 is set as B2', so as to obtain the lower and upper limits B1' and B2' of the second identification threshold; the third threshold factor is c1, c2, then the V2-c1 is set as C1', and V2+c2 is set as C2', so as to obtain the lower and upper limits C1' and C2' of the third identification threshold. Preferably, the magnitudes of the threshold factors may be the same or partially the same. For example, the values of a1, a2, b1, b2, c1, and c2 are the same, and all take Δe; alternatively, a1, a2 are all Δe1, b1, b2 are all Δe2, and c1, c2 are all Δe3.

Based on the identification threshold, the terminal device identifies the control functions of the three keys. After the calibration is completed, if the user operates any button, the earphone circuit will generate a voltage value V', and the control unit will compare the relationship between the voltage value V and the above-mentioned identification threshold, and identify the control function corresponding to the case according to the preset rules. For example, when A1'≤V'≤A2', it is recognized that the key SW1 (Key_OK) is operated, and the corresponding confirmation function is triggered; when B1'≤V'≤B2', it is recognized that the key SW3 (Key_V+) is operated operation, the corresponding volume increase function will be triggered. When C1'≤V'≤C2', it is recognized that the key SW2 (Key_V-) is operated, and the corresponding volume reduction function is triggered.

It is easy to understand that the number of buttons may be at least two, and the control functions corresponding to the buttons are not limited, but the principles are similar.

In this way, even if the headset is used for a period of time, hardware aging occurs, because the recognition threshold is set based on the electrical signal of the key after the hardware is aging, so that the terminal device can recognize the key pressed by the user.

In addition, the resistance values and/or working voltages of the earphone circuits of earphones of different manufacturers may be different, so when different earphones are used with the same mobile terminal, if the same recognition threshold is used, it will also cause the user to operate the buttons. , the terminal equipment cannot be identified or misidentified. The embodiment of the present invention can also solve this problem, because the terminal device can reset the recognition threshold according to each earphone, so as to recognize the buttons of different earphones.

Further, for the above-mentioned second manner, the above-described solution is: if at least one button fails, the voltage value generated by the user operating each button is collected, so as to determine the corrected recognition threshold. However, it is preferable to correct only the failed keys. For example, when the key SW1 (Key_OK) fails, the terminal device may only guide the user to operate the key SW1 (Key_OK) to obtain the voltage V1, and the other keys may not be corrected because they have not failed. Next, the control unit obtains the identification threshold of the failed key SW1 (Key_OK) according to the above-mentioned voltage V1 (for a specific setting method, see the above description, which will not be repeated here). This can also solve similar problems above.

Those of ordinary skill in the art can understand that all or part of the steps of implementing the above method embodiments can be completed by program instructions related to hardware, the aforementioned program can be stored in a computer-readable storage medium, and when the program is executed, execute It includes the steps of the above method embodiments; and the aforementioned storage medium includes: ROM, RAM, magnetic disk or optical disk and other media that can store program codes.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that it can still be The technical solutions described in the foregoing embodiments are modified, or some technical features thereof are equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (4)

1. A terminal device, wherein the terminal device comprises: input unit and output unit; The earphone interface is used for connecting with the earphone; the earphone includes at least two buttons, and the at least two buttons respectively correspond to a control function; operate to generate electrical signals; The control unit is used to prompt the user to perform headset correction when the control function corresponding to one of the at least two keys fails, and guide the user to operate the failed key through an image interface or voice; An electrical signal generated by the earphone circuit due to the failed key, and a recognition threshold is obtained according to the obtained electrical signal; The control unit is further configured to, after the user calibrates the headset, identify a control function corresponding to the failed key according to the identification threshold; wherein the identification threshold is a numerical range, including a lower limit value and an upper limit value. 2 . The terminal device according to claim 1 , wherein the at least two buttons comprise a first button and a second button, and the invalid one button is the first button, and correspondingly the acquiring the user operation An electrical signal generated by the earphone circuit due to an invalid button includes: acquiring a first electrical signal generated by the earphone when the user operates the disabled first button, and the first electrical signal is represented as a first value ; The control unit is configured to: obtain a lower limit value and an upper limit value of the identification threshold based on a first value represented by the first electrical signal and a first threshold factor. 3. The terminal device according to claim 2, wherein the control unit is further configured to: receiving a fifth electrical signal generated by the earphone circuit when the user operates the first button or the second button; comparing the magnitude relationship between the fifth electrical signal and the identification threshold; According to the comparison result, the control function corresponding to the fifth electrical signal is identified according to a preset rule. 4. The terminal device according to claim 3, wherein the control unit is specifically configured to: When the fifth electrical signal is greater than or equal to the lower limit of the identification threshold and less than or equal to the upper limit of the identification threshold, it is identified as a control function corresponding to the first key.