28.专用电路 a. dedicated circuit b. error control c. return signal 答案 突发性 a. bursty b. random c. header 答案:a 30.传输时延 a. destination address b. transmission delay c. return signal 答案:b 31.中间交换设备 a. given maximum b. intermediate switching equipment c. store-and-forward manner 答案:b 子网 答案 33.公众电信网 a. public telecommunication network b. intermediate switching node c. circuit- switched network 答案 4.半双工的 a. full-duplex b. half-duplex c. external call 答案:b 35.端局 a. toll center b. end office c. tandem switch 答案:b 36.外部呼叫 a. external call b. data traffic c. toll center 答案 37.链路 a. trunk b. link c. route 答案:b 38.交换节点 a. intermediate switching node b. voice-frequency circuit tching node 答案 39.音频电路 a. telephone subscriber b. voice-frequency circuit c. two wire connection 答案:b 40.拓扑 a. internodes b. topology c. route 答案:b28． 专用电路 a. dedicated circuit b. error control c. return signal 答案：a 29． 突发性 a. bursty b. random c. header 答案：a 30． 传输时延 a. destination address b. transmission delay c. return signal 答案：b 31． 中间交换设备 a. given maximum b. intermediate switching equipment c. store-and-forward manner 答案：b 32． 子网 a. header b. subnet c. busty 答案：b 33. 公众电信网 a. public telecommunication network b. intermediate switching node c. circuit- switched network 答案：a 34.半双工的 a. full-duplex b. half-duplex c. external call 答案：b 35. 端局 a. toll center b. end office c. tandem switch 答案：b 36. 外部呼叫 a. external call b. data traffic c. toll center 答案：a 37.链路 a. trunk b. link c. route 答案：b 38.交换节点 a. intermediate switching node b. voice-frequency circuit c. switching node 答案：c 39.音频电路 a. telephone subscriber b. voice-frequency circuit c. two wire connection 答案：b 40.拓扑 a. internodes b. topology c. route 答案：b