表達計算機數據終端的專業英語
學習計算機英語是一件很有用的東西，所以小編今天就給大家整理了有關於計算機的英語，有需要的可以多多參考一下哦
A simplified block diagram of a data communication link is shown in Fig.8-1. Although only one secondary is shown[1], it represents a typical secondary in a multipoint system. One of the functions of the host computer is to store the applications programs for the various secondaries.
The end equipment which either generates the digital information for transmission or uses the received digital data can be computers, printers, keyboards, CRTs, and so on. This equipment generally manipulates digital information internally in word units - the number of bits that make up a word in a particular piece of equipment are transferred in parallel. Digital data, when transmitted, are in serial form. Parallel transmission of an 8-bit word would require eight pairs of transmission lines - not at all cost-effective[3]. Data terminal equipment (DTE) is a general phrase encompassing all of the circuitry necessary to perform parallel-to-serial and serial-to-parallel conversions for transmission and reception respectively and for data link management. The UART (Universal Asynchronous Receiver/Transmitter) and USART(Universal Synchronous/Asynchronous Receiver/Transmitter) are the devices that perform the parallel-to-serial and serial-to-parallel conversions. The primary DTE includes a line control unit (LCU or LinCo) which controls the flow of information in a multipoint data link system. A station controller (STACO) is the corresponding unit at the secondaries. If there is software associated with the LCU, it is then called a front-end processor (FEP). At one time, the DTE was the last piece of equipment that belonged to the subscriber in a data link system. Between the DTEs, starting with the modems, was communications equipment owned and maintained by Telco[4]. Recent judgments have removed modems from the realm of exclusive Telco property.
Data communications equipment (DCE)[5] accepts the serial data stream from the DTE and converts it to some form of analog signal suitable for transmission on voice-grade lines. At the receive end, the DCE performs the reverse function of converting the received analog signal to a serial digital data stream. The simplest form of DCE is a modem (modulator/demodulator) or data set. At the transmit end, the modem can be considered a form of digital-to-analog converter, while at the receive end, it can be considered a form of analog-to-digital converter. The most common of modulation by modems are frequency shift keying (FSK), phase shift keying (PSK), and quadrature amplitude modulation (QAM). This is a typically data transmission mode using the analog telephone lines, see the bottom line between the two DCEs in Fig.8-1. If you transmit data by digital channel (sometimes it is called "Digital T-carrier[6]"), a Pulse Code Modulation (PCM) equipment must be used, see the middle part of Fig.8-1. A microwave transmission system can also be used for the data communication. Finally, you can use the satellite communication system for data transmission, non-shown in Fig.8-1.
If the cables and signal levels used to interconnect the DTE and DCE were left unregulated, the variations generated would probably be proportional to the number of manufacturers. Electronics industries Association (EIA), an organization of manufacturers concerned with establishing industry standards, have agreed on the RS-232C as the standard interface between the DTE and the modem. This is a 25-pin cable[7] whose pins have designated functions and specified signal levels. The RS-232C is anticipated to be replaced by an updated standard.
NOTES
[1] 從設備是指負責處理I/O和通信任務的設備。在大型通信系統中一般是指前端處理機FEP、線路控制器LCU;在微機組成的網絡中採用雙CPU的服務器，其中一個CPU可作爲從設備的控制部件。
[2] 圖中ROP-Read-Only Printers，早期計算機用的只作輸出的打印機，因爲當時還有一種鍵盤打印機，既可作爲輸出又可作爲輸入。
[3] 此句最後省略which is，即應爲which is not at all cost-effective.
[4] Telco是指美國所有進入公共電話網(PTN)的電話公司。
[5] DCE也稱爲數據電路終接設備Data Circuit-terminating Equipment.
[6] T-carrier源於美國貝爾公司的數字通信系統，將從音頻頻帶上來的信號轉換成數字脈衝，沿金屬線傳送稱爲T-carrier.
[7] cable：電纜，此處係指RS-232C標準使用的25針插座。
圖8-1是數據通信鏈路的簡化框圖，雖然圖中只畫了一個輔助設備，但它代表了多點系統中的典型輔助設備。主計算機的功能之一是存儲各種輔助設備的應用程序。
端設備可以是計算機、打印機、鍵盤、CRT等，它們可以生成要發送的數字信息，也可以使用所接收的數字數據，這種設備通常在內部以字爲單位處理數字信息——在一個實際設備中構成一個字的所有位是並行傳送的。數字數據在發送時是串行的。並行發送一個8位的字需要8對傳輸線，這是不經濟的。那些在發送、接收數據時分別完成並-串和串-並轉換並進行數據鏈路管理的所有電路，一般稱爲數據終端設備(DTE)。UART(通用異步接收/發送器)和USART(通用同步/異步接收/發送器)是實現並串和串並轉換的設備。基本的DTE包括用於控制多點數據鏈路系統中信息流的線路控制部件(LCU或LinCo)。輔助設備一方的相應設備是工作站控制器(STACO)。如果DTE有與LCU相關的軟件，則稱爲前端處理機(FEP)。同時，DTE也是數據鏈路系統中屬於用戶端的最後一個設備。在兩個DTE之間，先是調制解調器，接着是屬於並由電話公司維護的通信設備。最近的調整結果是調制解調器已不屬於電話公司獨家管理的設備了。
數據通信設備(DCE)從DTE接收串行數據流，並將其轉換成適合於在話音線路上發送的某種模擬信號形式。在接收端，DCE完成相反的功能，把接收到的模擬信號轉換成串行數字數據流。最簡單的DCE是調制解調器或數傳機。在發送端，調制解調器可以視爲一種數/模轉換器，而在接收端則可視爲一種模/數轉換器。調制解調器最常用的幾種調製方式是移頻鍵控(FSK)、移相鍵控(PSK)和正交調幅(QAM)。這是一種典型的使用模擬電話線路傳輸數據的方式，見圖8-1中兩個DCE之間底部的傳輸線。如果使用數字信道(有時稱爲數字T載波)傳輸數據，則應使用脈碼調製(PCM)設備，見圖8-1中間部分。也可以用微波傳輸系統進行數據通信。當然也可以用衛星通信系統傳輸數據，圖8-1中未畫出。
如果連接DTE和DCE的電纜和信號電平都是未調整的，則所產生的偏差量就可能與生產廠家的數量成正比。電子工業協會(EIA)，一個由建立行業標準的廠家組成的組織，同意將RS-232C作爲DTE和調制解調器間的標準接口。這是一個25針的電纜，每一針都規定了其功能及信號電平。預計RS-232C將被修訂的標準所取代。
