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
参考译文：
数据通信设备(DCE)从终端接受串行数据流，并将其转换为某种适合语音线路传输的模拟信号。在语音信号中，DCE的扮演着将接受的模拟信号转变成数字信号的作用。最简单的形式的DCE是一个调制解调器或数据接收器。在传输终端，调制解调器可以能够将数字信号再变成模拟信号，而在接收端，它可以被看作是一种形式的模数转换器。最常见的调制调制解调器频移键控（FSK信号），相移键控（PSK）和正交幅度调制（QAM）。如果电缆和信号电平用于互连的DTE和DCE留不受管制，产生的变化可能会proporation数量的制成品。电子工业协会评估（EIA），是一个相关建立行业标准组织，它已商定了RS-232C接口为标准的终端之间的接口和调制解调器。这是一个25针电缆引脚指定funtons和具有特定信号的电平。
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