200913756 九、發明說明： 【發明所屬之技術領域】 本發明係關於一種監視器音響電路。 【先前技術】 目如各類監視器如液晶監視器大部分都不含有揚聲 态，收聽音頻訊號時必須透過外接音箱來實現；亦有—L 監視器含有内置揚聲器，惟，習知技術之音量大小為不^ =，使用者使料非常不方便，而且音頻之訊噪比較低^ 耷音品質亦較差，同時其電路都是在傳統電路上設 一 件使用較多，成本較高。 °f ^ 【發明内容】 -立Γ於以上内容’有必要提供—種音量大小可調之監 另解决收心曰頻訊號時不能調節音奮女 之困難。 至八 令括一音頻電路及—揚聲 頻輸入連接器、-音頻輸入電路 電路、-音頻輸出電路、-第一音頻輸出、車 及-音量調節電路，該音頻輸入連接写一：：=， 機之音頻輪出連接器，另—端依序連接兮於接' 音頻放大電路、音頻輸出電路一二，入❸ 該揚聲器相連，該音旦+ 曰頻輸出連接器毛 微處理’與該音頻放大電路之間，盆用於接：：主機去 機板之微處理器之脈寬調變訊浐^視器 對應輸出給該音頻放 ^ 、’ x邊脈寬調變訊 大電路不同之電壓訊號，用於調節 200913756 音頻放大電路輸出之音頻訊號之音量大小。 -才目較習知技術，上述監視器音響電路包括一音 ^ ’該音量調節電路連接於監視器主機板之微處理器盘 二亥：頻放大電路之間，使得❹者可 電 路來調節音量之大小，使 曰里乃即電 【實施方式】 t用時更加方便，更具有人性化。 二閱圖1，本發明監視器音響電路之較佳實 括一音頻電路1〇及一揚整哭％ ^平1土貝％方式包 連接器30透過一 μ立 笔腦主機之音頻輸出 透苐一音頻線100將一音頻m泸耠a μ e i 頻電路10,該立箱却k 曰鴻訊戒輸入到該音 該揚聲哭2〇 $頻訊細該音頻電路1〇處理之後，由 龄視機50輸出。其中該音頻電路設置於 遍主機板（圖未示）上 °又置於 部或者監視器邊框上均可。知H又置於監視器内 該音頻電路10包括—音頻輸 入電路no、—音頻放大電路⑽、—；；10—曰頻輸 -第-音頻輸出逹接器15〇 一；:出電路14〇、 及—音量調節電踗l7n 弟一曰頻輸出連接器160 透過該第—%^ 音頻輸入連接器11〇一端用於 曰頻線1 〇 〇連接号ρ雪日似 德 3〇,另—端依序連接該音_入“機12之0曰i貝輸出連接器 150及第二音頻輸出連接哭頻輪出連接器 輸出連接器150之3 之一、相連’該第-音頻. 輪出連接器_^ 一 揚聲器2〇相連，該第二音頻 另一端用於 一 電路170之—端盥 耳機50 ’该音量調節 -、該曰頻放大電路13〇相連，另—端與監 200913756 視器主機板之微處理器40相連。 本發明監視器音響電路之較佳實施方式還包括一控制 按紐60 ’該控制按紐60設置於該監視器邊框上5且與該 監視器主機板之微處理器40相連，該控制按鈕60可以是 按鍵式，亦可以是旋轉式或者其他方式均可。 請一併參閱圖2,該音頻輸入電路120包括一第一電 感L1、一第二電感L2、一第一電容C1及一第二電容C2。 該第一電感L1之一端透過該第一電容C1與該音頻放大電 路130相連，該第二電感L2之一端透過該第二電容C2與 該音頻放大電路130相連，該第一電感L1和第二電感L2 之另一端均與該音頻輸入連接器110相連。該第一電感 L1、第二電感L2、第一電容C1及第二電容C2均產生濾 波之作用，用於濾除由該電腦主機之音頻輸出連接器30 輸入之音頻訊號中存在之雜波。 該音頻放大電路130包括一音頻放大器U、一電壓源 Vp及一第三電容C3·。該音頻放大器U之兩音量控制端DC1 和DC2均與該音量調節電路170相連，兩訊號輸入端IP1 和IP2分別與該第一電容C1和第二電容C2相連，第一到 第四訊號輸出端SP1+、SP1-、SP2 +和SP2-均與該音頻輸 出電路140相連，電源端V與該電壓源Vp相連；該第三 電容C3之一端與該電壓源Vp相連，另一端接地，用於消 除該電壓源Vp之干擾。 該音頻輸出電路140包括一第三電感L3、一第四電感 L4、一第五電感L5、一第六電感L6、一第七電感L7、一 9 200913756 .第八電感L8、一第四電容C4、一第五電容C5、一第六電 容C6、一第七電容C7、一第八電容C8及一第九電容C9。 該第三電感L3之一端依序連接該第四電容C4、第八電感 L8及第九電容C9後與該第二音頻輸出連接器160相連， 該第三電感L3之一端還透過該第六電容C6與該第二音頻 輸出連接器160相連，該第三電感L3之一端還直接與該 第一音頻輸出連接器150相連，該第三電感L3之另一端 與該音頻放大器U之第一訊號輸出端SP1 +相連；該第四 電感L4之一端依序連接該第五電容C5、第七電感L7及 第八電容C8後與該第二音頻輸出連接器160相連，該第 四電感L4之一端還透過該第七電容C7與第二音頻輸出連 接器160相連，該第四電感L4之一端還直接與該第一音 頻輸出連接器150相連，該第四電感L4之另一端與該音 頻放大器U之第三訊號輸出端SP2 +相連；該第五電感L5 之一端與該第一音頻輸出連接器150相連，另一端與該音 頻放大器U之第四訊號輸出端SP2-相連；該第六電感L6 之一端與該第一音頻輸出連接器150相連，另一端與該音 頻放大器U之第二訊號輸出端SP1-相連。該第四電容C4、 第五電容C5、第六電容C6、第七電容C7均為低電平濾波 電容，用於濾除該音頻輸出電路140中產生之低電平雜 波；該第八電容C8和第九電容C9均為高電平濾波電容， 用於濾除該音頻輸出電路140中產生之高電平雜波；該第 三電感L3、第四電感L4、第五電感L5、第六電感L6、第 七電感L7及第八電感L8均產生濾除電路中雜波之作用。 10 200913756 該音量調節電路170包括一電晶體Q1、一第一電阻R1、 一第二電阻R2、一第三電阻R3、一第四電阻R4、一第十 電容C10、一第十一電容C11及一第十二電容C12。該電 晶體Q1之射極E接地，集極C透過該第一電阻R1與一 電壓源Vcc相連，基極B透過該第三電阻R3接收該監視 器主機板之微處理器50之脈寬調變訊號；該第二電阻R2 之一端接地，另一端與該音頻放大器U之兩音量控制端 DC1和DC2均相連，該第二電阻R2之另一端還透過該第 四電阻R4與該電晶體Q1之集極C相連；該第十電容C10 之一端接地，另一端與該第二電阻R2與第四電阻R4之間 之節點相連；該第十一電容C11與該第十電容C10並聯連 接，該第十二電容C12與該第二電阻R2並聯連接。該第 十電容C10為低電平濾波電容，該第十一電容C11為高電 平濾波電容，產生濾除該音量調節電路170之雜波之作 用；該第一電阻R1、第二電阻R2及第四電阻R4為分壓 電阻，用於調節該音頻放大器U之兩音量控制端DC1和 DC2之電平。 下面對本發明之監視器音響電路之工作原理進行說 明。將該電腦主機之音頻輸出連接器30與音頻輸入連接器 110透過該第一音頻線100相連，當電腦主機播放一段音 頻訊號時，該音頻訊號即會透過該電腦主機之音頻輸出連 接器30、第一音頻線100輸入到該音頻電路10，透過該音 頻電路10處理之後由該揚聲器20或者耳機50輸出，使用 者即可收聽音頻訊號。 11 200913756 同時，使用者還可以透過該監視器邊框上之控制按鈕 60來調節音量大小。當使用者按下該監視器邊框上之控制 按鈕60時，該監視器主機板之微處理器40會相應產生不 同之脈寬調變訊號。該脈寬調變訊號為一方波訊號，其根 據該控制按鈕60之不同動作具有不同之工作週期。當該監 視器主機板之微處理器40產生之脈寬調變訊號處於高電 平時，該音量調節電路170之電晶體Q1導通，由於其射 極E接地，所以其集極C電平亦為低電平，此時該音量調 節電路170輸出低電壓訊號到該音頻放大電路130，即該 音頻放大器U之兩音量控制端DC1和DC2之電平為低電 平；當該監視器主機板之微處理器40產生之脈寬調變訊號 處於低電平時，該音量調節電路170之電晶體Q1截止， 此時該音量調節電路170輸出高電壓訊號到該音頻放大電 路130，即該音頻放大器U之兩音量控制端DC1和DC2 之電平為該電壓源Vcc之分壓電平，在本較佳實施方式中 即為該音量調節電路170之第二電阻R2之電壓。由於該 脈寬調變訊號為一方波訊號，所以該音頻放大器U之兩音 量控制端DC1和DC2之電平交替處於低電平與該分壓電 平之間，即會產生一等效電平，當該脈寬調變訊號之工作 週期不同時，該音頻放大器U之兩音量控制端DC1和DC2 之等效電平即不同，從而使該音頻放大器U輸出音量大小 不同，所以，透過調節該控制按姐60即可達到調節音量大 小之目的。 請一併參考圖3，其為該監視器主機板之微處理器40 12 200913756 產生之脈寬調變訊號之工作週期為1 : 2時，該音頻放大器 U之兩音量控制端DC1和DC2之電平VDC1和VDC2變 化狀態及等效電平圖，其中V代表該電壓源Vcc之分壓電 平，即該音量調節電路170之第二電阻R2之電壓，VI代 表該兩音量控制端DC1和DC2之等效電平，即1/2V，方 波代表該兩音量控制端DC1和DC2之電平VDC1和VDC2 變化狀態。由於該音頻放大器U之兩音量控制端DC1和 DC2相連，所以VDC1和VDC2相等。 請繼續一併參考圖4,其為該監視器主機板之微處理 器40產生之脈寬調變訊號之工作週期為1 ·· 4時，該音頻 放大器U之兩音量控制端DC1和DC2之電平VDC1和 VDC2變化狀態及等效電平圖，其中V代表該電壓源Vcc 之分壓電平，即該音量調節電路170之第二電阻R2之電 壓，V2代表該音頻放大器U之兩音量控制端DC1和DC2 之等效電平，即1/4V，方波代表該兩音量控制端DC1和 DC2之電平VDC1和VDC2變化狀態。由於該音頻放大器 U之兩音量控制端DC1和DC2相連，所以VDC1和VDC2 相等。 該音頻電路10中包含有複數個電感及電容，該電感及 電容均產生濾波作用，用於濾處電路中之雜波，從而可以 使得使用者收聽到音質較高之音頻訊號。 以上該電腦主機還可以是其他能夠播放音頻訊號之主 機，比如CD播放機、VCD播放機與DVD播放機等。 採用上述監視器音響電路，可以直接將一耳機50與該 13 200913756 第二音_出連接器⑽相連或者直接透過揚聲請即可 =曰頻。fL號’並且使用者可以透過監視器邊框上之控制 =〇來調節音量大小，方便實用；同時整個監視器音響 J知用之電子兀件少，成本較低。 綜上所述， 提出專利申請。 實施例，舉凡熟 精神所作之等效 5青專利範圍内。 本發明符合發明專 惟，以上所述者僅 悉本案技藝之人士 修飾或變化，皆應 利要件，爰依法 為本發明之較佳 ’在差依本發明 涵蓋於以下之申 【圖式簡單說明】 盗音響電路之較佳實施方式之工作 圖1係本發明監視 原理框圖。 係圖1中音頻電路之電路圖。 圖3係本發明監視器音每 調變訊號之卫作週期為彳”二敎方式中脈寬 電平示意圖。 ’、蚪曰頻放大器之音量控制端之 圖4係本發明監视器音塑雷$ 調變訊號之工作週期.:日=佳實施方式中脈寬 電平示意圖。 守0頻放大益之音量控制端之 【主要元件符號說明】 音頻電路 音頻輪入電路 音頻輪出電路 第二音頻輪出連接器 音頻輸入連接器 120音頻放大電路 140第一音頻輸出連接器 160音量調節電路 110 130 150 170 14 200913756 揚聲器 20 電腦主機之音頻輸出連接器 30 監視器主機板之微處理器 40 耳機 50 控制按鈕 60 第一音頻線 100 第一電阻 R1 第二電阻 R2 第三電阻 R3 第四電阻 R4 第一電感 L1 第二電感 L2 第三電感 L3 第四電感 L4 第五電感 L5 第六電感 L6 第七電感 L7 第八電感 L8 第一電容 C1 第二電容 C2 第三電容 C3 第四電容 C4 第五電容 C5 第六電容 C6 第七電容 C7 第八電容 C8 第九電容 C9 第十電容 CIO 第十一電容 C11 第十二電容 C12 電晶體 ‘ Q1 電源端 V 音頻放大器 U 音量控制端 DC1 、DC2 訊號輸出端 SP1 +、SP1-、SP2+、SP2- 電壓源 Vcc 、Vp 訊號輸入端 IP1 ' IP2 15200913756 IX. Description of the Invention: TECHNICAL FIELD OF THE INVENTION The present invention relates to a monitor sound circuit. [Prior Art] For example, most types of monitors, such as LCD monitors, do not contain a loud sound state. When listening to audio signals, they must be realized through external speakers. Also, the -L monitors have built-in speakers, but the conventional technology The volume is not ^ ^, the user makes the material very inconvenient, and the audio signal noise is relatively low ^ The sound quality is also poor, and the circuit is more used on the traditional circuit, the cost is higher. °f ^ [Invention] - Based on the above content, it is necessary to provide a monitor with adjustable volume. Another difficulty in adjusting the sound signal can not be adjusted. Up to eight-in-one audio circuit and - speaker input connector, - audio input circuit, - audio output circuit, - first audio output, car and - volume adjustment circuit, the audio input connection writes one::=, machine The audio wheel is out of the connector, and the other end is connected in sequence to the 'audio amplification circuit, the audio output circuit is one or two, and the speaker is connected to the speaker. The sound + 曰 frequency output connector is micro-processed' and the audio is amplified. Between the circuits, the basin is used to connect: the pulse width modulation of the microprocessor of the host to the board is output to the audio channel, and the voltage signal of the x-side pulse width modulation is different. It is used to adjust the volume of the audio signal output by the 200913756 audio amplifier circuit. - Compared with the prior art, the above monitor audio circuit includes a sound control circuit connected to the microprocessor board of the monitor motherboard: the frequency amplifying circuit, so that the circuit can adjust the volume. The size of the , is the electricity [implementation] t is more convenient and more user-friendly. 2, FIG. 1 shows a preferred embodiment of the monitor audio circuit of the present invention, an audio circuit 1 and a raised crying % ^ 1 ton % mode package connector 30 through a μ vertical pen brain audio output An audio line 100 will have an audio m泸耠a μ ei frequency circuit 10, and the vertical box is k 曰 讯 戒 戒 输入 输入 输入 该 该 该 该 该 该 频 频 频 频 频 频 频 频 频 频 频 频 该 该 音频 该 音频 音频 音频 音频Video camera 50 output. The audio circuit is disposed on the main board (not shown) and placed on the monitor or the monitor frame. The audio circuit 10 is placed in the monitor, and the audio circuit 10 includes an audio input circuit no, an audio amplifier circuit (10), a 10-pin frequency-first audio output connector, and an output circuit. , and - volume adjustment switch l7n brother a frequency output connector 160 through the first -% ^ audio input connector 11 〇 one end for the 曰 frequency line 1 〇〇 connection number ρ snow day like de 3 〇, another - The terminal sequentially connects the sound_into the 0曰i output connector 150 of the machine 12 and the second audio output connection one of the crying frequency out connector output connector 150, connected to the 'the first audio. Connector _^ A speaker 2 〇 is connected, the other end of the second audio is used for a circuit 170 - the end of the earphone 50 'the volume adjustment - the 曰 frequency amplification circuit 13 〇 connected, the other end and the monitor 200913756 The microprocessor 40 of the motherboard is connected. The preferred embodiment of the monitor audio circuit of the present invention further includes a control button 60'. The control button 60 is disposed on the monitor frame 5 and is opposite to the monitor motherboard. The processor 40 is connected, and the control button 60 can be a button type or a rotation. For example, the audio input circuit 120 includes a first inductor L1, a second inductor L2, a first capacitor C1, and a second capacitor C2. The first inductor L1 One end of the second inductor L2 is connected to the audio amplifying circuit 130 through the second capacitor C2, and the other end of the first inductor L1 and the second inductor L2 are connected to the audio amplifier circuit 130. Connected to the audio input connector 110. The first inductor L1, the second inductor L2, the first capacitor C1, and the second capacitor C2 each generate a filtering function for filtering the input of the audio output connector 30 of the computer host. The audio amplifying circuit 130 includes an audio amplifier U, a voltage source Vp and a third capacitor C3. The two volume control terminals DC1 and DC2 of the audio amplifier U are connected to the volume adjusting circuit. 170 is connected, two signal input terminals IP1 and IP2 are respectively connected to the first capacitor C1 and the second capacitor C2, and the first to fourth signal output terminals SP1+, SP1-, SP2+ and SP2- are connected to the audio output circuit 140. , the power terminal V and the electricity The source of the third capacitor C3 is connected to the voltage source Vp, and the other end is grounded to cancel the interference of the voltage source Vp. The audio output circuit 140 includes a third inductor L3 and a fourth inductor L4. a fifth inductor L5, a sixth inductor L6, a seventh inductor L7, a 9 200913756. an eighth inductor L8, a fourth capacitor C4, a fifth capacitor C5, a sixth capacitor C6, a seventh capacitor C7 An eighth capacitor C8 and a ninth capacitor C9. One end of the third inductor L3 is sequentially connected to the fourth capacitor C4, the eighth inductor L8 and the ninth capacitor C9, and is connected to the second audio output connector 160. One end of the third inductor L3 is further connected to the second audio output connector 160 through the sixth capacitor C6. One end of the third inductor L3 is also directly connected to the first audio output connector 150. The third inductor L3 is connected. The other end is connected to the first signal output end SP1 + of the audio amplifier U; one end of the fourth inductor L4 is sequentially connected to the fifth capacitor C5, the seventh inductor L7 and the eighth capacitor C8, and the second audio output The connector 160 is connected, and one end of the fourth inductor L4 also passes through the The seventh capacitor C7 is connected to the second audio output connector 160. One end of the fourth inductor L4 is also directly connected to the first audio output connector 150. The other end of the fourth inductor L4 is connected to the third signal of the audio amplifier U. The output end SP2 + is connected; one end of the fifth inductor L5 is connected to the first audio output connector 150, and the other end is connected to the fourth signal output end SP2- of the audio amplifier U; one end of the sixth inductor L6 is The first audio output connector 150 is connected, and the other end is connected to the second signal output terminal SP1- of the audio amplifier U. The fourth capacitor C4, the fifth capacitor C5, the sixth capacitor C6, and the seventh capacitor C7 are low-level filter capacitors for filtering low-level noise generated in the audio output circuit 140; the eighth capacitor C8 and ninth capacitor C9 are high-level filter capacitors for filtering high-level clutter generated in the audio output circuit 140; the third inductor L3, the fourth inductor L4, the fifth inductor L5, and the sixth The inductor L6, the seventh inductor L7, and the eighth inductor L8 all function to filter out clutter in the circuit. 10 200913756 The volume adjustment circuit 170 includes a transistor Q1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a tenth capacitor C10, and an eleventh capacitor C11. A twelfth capacitor C12. The emitter E of the transistor Q1 is grounded, the collector C is connected to a voltage source Vcc through the first resistor R1, and the base B receives the pulse width adjustment of the microprocessor 50 of the monitor motherboard through the third resistor R3. a variable signal; one end of the second resistor R2 is grounded, the other end is connected to the two volume control terminals DC1 and DC2 of the audio amplifier U, and the other end of the second resistor R2 is further transmitted through the fourth resistor R4 and the transistor Q1 The collector C is connected; one end of the tenth capacitor C10 is grounded, and the other end is connected to a node between the second resistor R2 and the fourth resistor R4; the eleventh capacitor C11 is connected in parallel with the tenth capacitor C10, The twelfth capacitor C12 is connected in parallel with the second resistor R2. The tenth capacitor C10 is a low level filter capacitor, and the eleventh capacitor C11 is a high level filter capacitor, which generates a function of filtering out the noise of the volume adjustment circuit 170; the first resistor R1 and the second resistor R2 and The fourth resistor R4 is a voltage dividing resistor for adjusting the levels of the two volume control terminals DC1 and DC2 of the audio amplifier U. The operation of the monitor audio circuit of the present invention will now be described. The audio output connector 30 of the computer is connected to the audio input connector 110 through the first audio cable 100. When the computer host plays an audio signal, the audio signal passes through the audio output connector 30 of the computer host. The first audio line 100 is input to the audio circuit 10, and is processed by the audio circuit 10 and outputted by the speaker 20 or the earphone 50, so that the user can listen to the audio signal. 11 200913756 At the same time, the user can also adjust the volume through the control button 60 on the border of the monitor. When the user presses the control button 60 on the border of the monitor, the microprocessor 40 of the monitor motherboard will generate different pulse width modulation signals accordingly. The pulse width modulation signal is a one-way signal, which has different duty cycles according to different actions of the control button 60. When the pulse width modulation signal generated by the microprocessor 40 of the monitor motherboard is at a high level, the transistor Q1 of the volume adjustment circuit 170 is turned on, and since the emitter E is grounded, the collector C level is also Low level, at this time, the volume adjustment circuit 170 outputs a low voltage signal to the audio amplification circuit 130, that is, the levels of the two volume control terminals DC1 and DC2 of the audio amplifier U are low; when the monitor board is When the pulse width modulation signal generated by the microprocessor 40 is at a low level, the transistor Q1 of the volume adjustment circuit 170 is turned off, and the volume adjustment circuit 170 outputs a high voltage signal to the audio amplification circuit 130, that is, the audio amplifier U. The level of the two volume control terminals DC1 and DC2 is the voltage dividing level of the voltage source Vcc, which is the voltage of the second resistor R2 of the volume adjusting circuit 170 in the preferred embodiment. Since the pulse width modulation signal is a one-way signal, the levels of the two volume control terminals DC1 and DC2 of the audio amplifier U alternate between a low level and the divided voltage level, that is, an equivalent level is generated. When the duty cycle of the pulse width modulation signal is different, the equivalent levels of the two volume control terminals DC1 and DC2 of the audio amplifier U are different, so that the output volume of the audio amplifier U is different, so by adjusting the Controlling the sister 60 can achieve the purpose of adjusting the volume. Please refer to FIG. 3 together, when the duty cycle of the pulse width modulation signal generated by the microprocessor 40 12 200913756 of the monitor motherboard is 1:2, the two volume control terminals DC1 and DC2 of the audio amplifier U Level VDC1 and VDC2 change state and equivalent level diagram, where V represents the voltage division level of the voltage source Vcc, that is, the voltage of the second resistor R2 of the volume adjustment circuit 170, and VI represents the two volume control terminals DC1 and The equivalent level of DC2, that is, 1/2V, represents the change state of the levels VDC1 and VDC2 of the two volume control terminals DC1 and DC2. Since the two volume control terminals DC1 and DC2 of the audio amplifier U are connected, VDC1 and VDC2 are equal. Please refer to FIG. 4 together, when the duty cycle of the pulse width modulation signal generated by the microprocessor 40 of the monitor motherboard is 1 ··4, the two volume control terminals DC1 and DC2 of the audio amplifier U Level VDC1 and VDC2 change state and equivalent level diagram, where V represents the voltage division level of the voltage source Vcc, that is, the voltage of the second resistor R2 of the volume adjustment circuit 170, and V2 represents the volume of the audio amplifier U. The equivalent level of the control terminals DC1 and DC2, that is, 1/4V, represents a change state of the levels VDC1 and VDC2 of the two volume control terminals DC1 and DC2. Since the two volume control terminals DC1 and DC2 of the audio amplifier U are connected, VDC1 and VDC2 are equal. The audio circuit 10 includes a plurality of inductors and capacitors, and the inductors and capacitors are filtered to filter the clutter in the circuit, so that the user can listen to the audio signal with higher sound quality. The above computer host can also be other hosts capable of playing audio signals, such as CD players, VCD players and DVD players. With the above monitor audio circuit, one earphone 50 can be directly connected to the 13 200913756 second sound_out connector (10) or directly through the speaker sound. The fL number 'and the user can adjust the volume through the control on the monitor frame = 〇, which is convenient and practical; at the same time, the entire monitor sound knows that the electronic components are less and the cost is lower. In summary, a patent application is filed. The embodiment is equivalent to the equivalent of the 5 Green patent. The invention is in accordance with the invention, and the above-mentioned ones only know the modification or change of the person skilled in the present invention, and all of them should be advantageous, and the invention is better according to the law. The invention is covered by the following claims. Fig. 1 is a block diagram showing the monitoring principle of the present invention. Figure 1 is a circuit diagram of the audio circuit in Figure 1. 3 is a schematic diagram of the pulse width level of the monitor tone per modulation signal of the present invention in the "敎" mode, and the volume control terminal of the chirped frequency amplifier is the monitor sound of the present invention. Thunder $ modulation signal working cycle.: Day = good implementation mode pulse width level diagram. Suppressed 0 frequency amplification of the volume control end of the [main component symbol description] audio circuit audio wheeled circuit audio wheel circuit second Audio wheel connector audio input connector 120 audio amplifier circuit 140 first audio output connector 160 volume adjustment circuit 110 130 150 170 14 200913756 speaker 20 computer host audio output connector 30 monitor motherboard microprocessor 40 headset 50 control button 60 first audio line 100 first resistor R1 second resistor R2 third resistor R3 fourth resistor R4 first inductor L1 second inductor L2 third inductor L3 fourth inductor L4 fifth inductor L5 sixth inductor L6 Seven inductor L7 eighth inductor L8 first capacitor C1 second capacitor C2 third capacitor C3 fourth capacitor C4 fifth capacitor C5 sixth capacitor C6 seventh capacitor C7 eighth Capacitor C8 ninth capacitor C9 tenth capacitor CIO eleventh capacitor C11 thirteenth capacitor C12 transistor 'Q1 power terminal V audio amplifier u volume control terminal DC1, DC2 signal output terminal SP1 +, SP1-, SP2+, SP2- voltage Source Vcc, Vp signal input IP1 ' IP2 15