Data communications equipment(DEC)  (1)  the serial data stream from the DTE and converts it to some form of  (2)  suitable of transmission on voice grade lines. At the  (3)  , the DCE performs the reverse function of convering the received analog signal to serial digital data stream .The simplest form of DCE is a (4) or data set. At the transmit end, the modem can be considered a form of  (5)  , while at the receive end, it can be considered a form of analog to digital converter. The most common forms of modulation by modems are frequency shift keying(FSK), phase shift keying(PSK), and quadrature amplitude modulation(QAM). If the cables and signal levels used to interconnect the DTE and DCE were left unregulated,the variations generated would probably be proporation to the number of manufactures. Electronics Industries Association(EIA), an organization of manufactuuers 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 pins have designated funtons and specified signal levels.

 (1) A. accepts       B.sends         C.delivers      D.receives

 (2) A. digital signal   B.analog signal  C.light signal    D.sound signal

 (3) A. back end      B.front end      C.sending end   D.receive end

 (4) A. modem       B.cpu           C.demodulator   D.modulator.

 (5) A. host computer               B.digital to analog converter 

    C. analog to digital converter     D.secondaries#p#

答案：
1、A   2、B   3、D   4、A   5、B

參考譯文：

數(shù)據(jù)通信設(shè)備(DCE)從終端接受串行數(shù)據(jù)流，并將其轉(zhuǎn)換為某種適合語(yǔ)音線路傳輸?shù)哪M信號(hào)。在語(yǔ)音信號(hào)中，DCE的扮演著將接受的模擬信號(hào)轉(zhuǎn)變成數(shù)字信號(hào)的作用。最簡(jiǎn)單的形式的DCE是一個(gè)調(diào)制解調(diào)器或數(shù)據(jù)接收器。在傳輸終端，調(diào)制解調(diào)器可以能夠?qū)?shù)字信號(hào)再變成模擬信號(hào)，而在接收端，它可以被看作是一種形式的模數(shù)轉(zhuǎn)換器。最常見(jiàn)的調(diào)制調(diào)制解調(diào)器頻移鍵控（FSK信號(hào)），相移鍵控（PSK）和正交幅度調(diào)制（QAM）。如果電纜和信號(hào)電平用于互連的DTE和DCE留不受管制，產(chǎn)生的變化可能會(huì)proporation數(shù)量的制成品。電子工業(yè)協(xié)會(huì)評(píng)估（EIA），是一個(gè)相關(guān)建立行業(yè)標(biāo)準(zhǔn)組織，它已商定了RS-232C接口為標(biāo)準(zhǔn)的終端之間的接口和調(diào)制解調(diào)器。這是一個(gè)25針電纜引腳指定funtons和具有特定信號(hào)的電平。
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