题目内容

7（）

A. progressed
B. generated
C. developed
D. advanced

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5（）

A. bestowed
B. given
C. presented
D. endowed

同步数字系列（SDH）是光纤信道复用标准，其中最常用的STM-1（OC-3）据速率是（），STM-4（OC-12）的数据速率是（）。同步数字系列（SDH）是光纤信道复用标准，其中最常用的STM-1（OC-3）据速率是（）

A. 155.520Mb/s
B. 622.080Mb/s
C. 2488.320Mb/s
D. 10Gb/s

Although a given waveform may contain frequencies over a very broad range, as a practical matter any transmission system will be able to accommodate only a limited band of （） . This, in turn, limits the data rate that can be carried on the transmission （） . A square wave has an infinite number of frequency components and hence an infinite （） .However, the peak amplitude of the kth frequency component, kf, is only 1/k, so most of the （） in this waveform is in the first few frequency components. In general, any digital waveform will have （） bandwidth. If we attempt to transmit this waveform as a signal over any medium, the transmission system will limit the bandwidth that can be transmitted. A square wave has an infinite number of frequency components and hence an infinite（）

A. source
B. bandwidth
C. energy
D. cost

[问题4]公司网络中的设备或系统(包括存储商业机密的数据库服务器、邮件服务器、存储资源代码的PC机、应用网关、存储私人信息的PC机、电子商务系统)哪些应放在DMZ中，哪些应放在内网中给予简要说明。