⑴A.32位 B.64位 C.128位 D.256位

　　⑵A.20字節 B.40字節 C.60字節 D.256字節

　　⑶A.校驗和 B.差錯控制 C.流量控制 D.糾錯

　　⑷A.冒號十六進制B.十進制 C.冒號八進制 D.二進制

　　⑸A.雙協議站 B.多協議棧 C.協議路由器 D.隧道技術

　　答案：CBAAD

　　The Integrated Services Digital Network(ISDN) is a set of international standards for access to advanced,all-digital public _(1)_network.

　　ISDN standards have been defined by the _(1)_,a branch of the United Nations’ Internaational Telecommunications Union (ITU), in the series I and Q recommendations.

　　There are five ISDN Standard Devices.A_(1)_ is any piece of communicating equipment that complies with the ISDN standard. _(1)_performs the logical interface functions of switching and local-device control. _(1)_performs the physical interface conversion between the dissimilar customer and network sides of the interface.

　　⑴A.information B.telecommunications C.global D.local

　　⑵A.ITU-T B.ITU-U C. ITU-A D. ITU-R

　　⑶⑷⑸A.TA B.TE C.NT1 D.NT2 E.ET

　　Answer：BABCD