家庭接入Internet可以通过光缆入户，即(56)方式，也可以通过传统的线缆接入。当使用电话线接入时，有多种模式，对称模式的技术有(57)。ADSL接入铜线的传输距离可达(58)km，通过多路复用技术，这个线路上可同时存在(59)个信道。当使用HFC方式时，用户端需要CABLE　Modem，它提供的连接是(60)。

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In the following essay, each blank has four choices. Choose the best answer and write down on the answer sheet.

 Spread spectrum simply means that data is sent in small pieces over a number of the(71)frequencies available for use at any time in the specified range. Devices using(72)spread spectrum(DSSS)communicate by(73)each byte of data into several parts and sending them concurrently on different(74). DSSS uses a lot of the available(75), about 22 megahertz(MHz).

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For each blank, choose the best answer from the four choices and write down on the answer sheet.

(66)is a protocol that a host uses to inform. a router when it joins or leaves an Internet multicast group.

(67)is an error detection code that most data communication networks use.

(68)is an interior gateway protocol that uses a distance vector algorithm to propagate routing information.

(69)is a transfer mode in which all types of information are organized into fixed form. cells on an asynchronous or non-periodic basis over a range of media.

(70)is an identifier of a web page.