【正文】 for its 16way input, the output of five trade unions Road. It is Chinese characters superimposed clock system uptime enquiries, a powerful builtin functions such as Chinese Character Library. It is critical to provide the relevant 4 agreements for secondary development. The software is to use some of the major video capture card provided by the API function and video switching matrix provided by the munication protocol software and services produced receive software, which is oneway video signals and control signals are twoway. Through LAN control mands can be issued. Conclusion This paper illustrates how the present technological conditions, assembled into one economical and reliable, and patible with the advanced monitoring system. This system suited to the local area work (10/100 M) on the realtime transmission of digital video images. Multimedia is a simple monitoring system (including video only). Believe that with puter technology, video technology, control technology, munications technology development, work monitoring will also enjoy broad prospects. An analogtodigital converter An analogtodigital converter(ADC) is used to convert a continuously variable signal to a corresponding digital form which can take any one of a fixed number of possible binary values. If the output of the transducer does not vary continuously, no ADC is necessary. In this case the signal conditioning section must convert the ining signal to a form which can be connected directly to the next part of the interface, the input/output section of the microputer itself. The I/O section converts digital “on/off” voltage signals to a form which can be presented to the processor via the system buses. Here the state of each input line, whether it is “on” or “off”, is indicated by a corresponding “1” or “0”. In the analog inputs which have been converted to digital form, the patterns of ones and zeros in the internal representation will form binary numbers corresponding to the quantity being converted. Feedback Control The class of control problems to be examined here is one of considerable engineering interest. We shall consider systems with several inputs, some known as controls because they may be manipulated and others called external disturbances, which are quite unpredictable. For example, in an industrial furnace we may consider the fuel flow, the ambient temperature, and the loading of material into the furnace to be inputs. Of these, the fuel flow is accessible and can readily be controlled, while the latter two are usually unpredictable disturbances. In such situations, one aspect of the control problems is to determine how the controls should be manipulated so as to counteract the effects of the external disturbances on the state of the system. One possible approach to the solution of this problem is to use a continuous measurement of the disturbances, and from this and the known system equations to determine what the control inputs should be as functions of time to give appropriate control of the system state. Digital Interface Circuits The signals used within microputer circuits are almost always too small to be connected directly to the “outside world” and some kind of interface must be used to translate them to a more appropriate form. The design of section of interface circuits is one of the most important tasks facing the engineer wishing to apply microputers. We have seen that in microputers information is represented as discrete patterns of bits。系統(tǒng)通過遙控攝像機及其輔助設(shè)備（鏡頭、云臺等），直接觀察被監(jiān)視場所的情況，同時可以把被監(jiān)視場所的情況進(jìn)行同步錄象。在控制中心，只要一個工作人員的操作，就能夠觀察多個被控區(qū)域，以及遠(yuǎn)距離區(qū)域的監(jiān)控功能，這就是監(jiān)控系統(tǒng)在現(xiàn)代建筑中起獨特作用和被廣泛應(yīng)用的重要原因。與此同時，硬盤錄像系統(tǒng)的數(shù)字化和傳輸網(wǎng)絡(luò)化等先進(jìn)技術(shù)可以實現(xiàn)與防盜報警等系統(tǒng)聯(lián)網(wǎng)聯(lián)動，及時準(zhǔn)確地反饋現(xiàn)場信息，為報警事件提供充分可靠的依據(jù)。 3．選擇性能價格比較高的設(shè)備，根據(jù)項目的特點配置系統(tǒng)的設(shè)備，既要符合先進(jìn)性的原則和安防系統(tǒng)規(guī)范的要求，又要盡量考慮為學(xué)校節(jié)省工程費用。根據(jù)國家有關(guān)技術(shù)規(guī)范，系統(tǒng)應(yīng)設(shè)置安防攝像機，電視監(jiān)視器、錄像機（或硬盤錄像機）和畫面處理器等，使用戶能隨時調(diào)看任意一個畫面， 8 遙控操作任一臺攝像機等。 模擬 數(shù)字轉(zhuǎn)換器（ ADC）用來將連續(xù)變化信號變成相應(yīng)的數(shù)字量，這數(shù)字 量可是可能性的二進(jìn)制數(shù)值中的一固定值。這里每一根線的狀態(tài)，無論是“開”或是“關(guān)”，用相應(yīng)的“ 1”或“ 0”表示。我們所討論的系統(tǒng)有幾個輸入，其中某些輸入稱為控制量，因為這些量是可以人為地控制的，而另一些輸入稱為外部擾動，它們是很難預(yù)知的。 數(shù)字接口電路 在微機電路中使用的信號幾乎總是太小而不能被直接地連到“外部世界”，因而必須用某種形式將其轉(zhuǎn)換成更適宜的形式。 連接邏輯電路時，必須小心翼翼，以保證它們的邏輯電平和電流額定值是兼容的。 對于輸入接口，也許設(shè)計所面臨的主要問題是電噪聲，小噪聲信號會引起系統(tǒng)工作不良，而大量的噪聲會造成永久性損壞。 3． 用一對二極管以反向偏置于正常方向的形式連接至電源端，來保護(hù)過高的輸入電壓。兩種方式都可用于低功率電路中，但只有串聯(lián)連接才能用于高功率電路，這是因為串聯(lián)電阻R 上要消耗功率 89C52 主要性能參數(shù)： 與 MCS— 51產(chǎn)品指令和引腳完全兼容 ， 8K字節(jié)可重擦寫 Flash閃速存儲器 1000次擦寫周期 ， 全靜態(tài)操作： 0Hz— 20Mz， 三級加密程序存儲器 ， 32個可編程 I/O口線 ， 3個 16位定時 /計數(shù)器 ， 8個中斷源 ， 可編程串行 UART通道 ， 低功耗空閑和掉電模式 功能特性概述： AT89C52提供以下標(biāo)準(zhǔn)功能： 8K字節(jié) Flash內(nèi)存閃速存儲器， 256字節(jié)內(nèi)部 RAM， 32個I/O口線， 3個 16位定時 /計數(shù)器，一個 6向量兩極中斷結(jié)構(gòu)，一個全雙工串行通信口，片內(nèi)振蕩器及時鐘電路。 定時器 2 定時器 2是一個 16位定時 /計數(shù)器，它既可當(dāng)定時器使用，也可以作為外部事件計數(shù)器使用，其工作方式由特殊功能寄存器 T2CON的（如表 2）的 C/T2位選擇。若在第一個機器周期中采到的值為 1，而在下 一個機器周期中采到的值是為 0，則在緊跟著的下一個周期的 S3P1期間寄存器加 1。如果 EXEN=0，定時器 2是一個 16位定時器或計數(shù)器，計數(shù)溢出時，對 T2CON的溢出標(biāo)志 TF2的位置，同時激活中斷。當(dāng) DCEN置位時，定時器既可向上計數(shù)，這取決于 T2EX引腳的值。 波特率發(fā)生器 當(dāng) T2CON（表 3）中的 TCLK和 RCLK置位時，定時 /計數(shù)器 2作為波特率發(fā)生器使用。在方式 1和方式 3中，波特率由定時器 2的溢出速率根據(jù)下式確定： 定時器既能工作于定時方式也能工作于計數(shù)方式，在大多數(shù)的應(yīng)用中，是工作在定時方式（ C/T2=0）。所以，當(dāng)定時器 2作為波特率發(fā)生器使用時， T2EX可作為附加的外部中斷源來使用，需要注意的是，當(dāng)定時器 2工作于波特率器時，作為定時器運行（ TR2=1）時，并不能訪問 TH2和 TL2。 11