9．PCM異步復(fù)接二次群的幀長度為(      )

A．848bit  

B．820bit

C．256bit                                                       

D．212bit

10．PCM一次群的接口碼型為(      )

A．HDB₃碼                                                    

B．AMI碼

C．CMI碼                                                      

D．HDB₃碼或CMI碼

11．可以采用1+l保護(hù)方式的自愈環(huán)有(      )

A．二纖單向通道倒換環(huán)

B．二纖雙向通道倒換環(huán)

C．二纖單向復(fù)用段倒換環(huán)

D．二纖單向通道倒換環(huán)和二纖雙向通道倒換環(huán)

12．沒有誤碼增殖的基帶傳輸碼型是(      )

A．AMI碼                                                     

B．CMI碼

C．HDB₃碼                                                    

D．AMI碼和CMI碼

13．再生中繼系統(tǒng)的特點(diǎn)為(      )

A．無噪聲積累                                               

B．有誤碼率的積累

C．無誤碼率的積累                                        

D．無噪聲積累和有誤碼率的積累

14．?dāng)?shù)字通信系統(tǒng)(傳送話音信號)誤碼率應(yīng)低于(      )

A．10^-5                                                           

B．10^-6

C．10^-7                                                           

D．10^-8

15．光纖數(shù)字傳輸系統(tǒng)屬于(      )

A．頻帶傳輸                                                  

B．基帶傳輸

C．?dāng)?shù)字?jǐn)?shù)據(jù)傳輸                                           

D．無線傳輸