通过窄带ISDN上网，用户可以使用的最大数据速率是______Kbit/s。
A．55.6
B．64
C．128
D．144
参考答案：C
解析：ISDN有两个速率接口：基本速率接口(BRI)和基群速率速口(PRI)。其中基本速率接口是以普通电话的用户线做ISDN用户线，同时提供两条速率均为64kb/s的B信道和一条速率为16kb/s的D信道的接口，即“2B+D”接口，B信道负责传输数据，D信息用于传输信令。
用方框内单词的适当形式填空。(请将答案写在答题卡对应题号的横线上。)
小题2:His refusal was worded in such a __________way that we could not be offended. 小题3:___________in the southeast of China, .Shanghai is a famous fashion centre. 小题4:___________ with the difficulty, we shouldn’t give up. 小题5:This kind of activity was first held in a _____________country like China. 小题6:Being ___________at a normal school is necessary for a child. 小题7:A lot of people are dying of __________ in many parts of the world. 小题8:Smoking and drinking are lifestyles. 小题9:As her daughter hadn’t returned home, the mother was looking out of the window all the time. 小题10:Many countries send messages of _____________ to China after the Shenzhou V landed safely this morning. |