英语_电子信息工程12.pptVIP

　　It is a distinct possibility that narrowband ISDN, with its rigid channelization and relatively low data rates, will never capture more than a modest share of the market for business-oriented data services, increasingly served by packet-switched LANs and MANs. Its board-band descendants, promising both high-speed packet switching and a range of switched channel rates extending into the hundreds of megabits per second, may become more pervasive. In any case, it is virtually certain that digital access and out-of-band signaling will sooner or later be made available to almost all subscribers of the public network. NOTES 　　[1]? It will mediate human-machine interactions that are inseparable parts of many customer applications, and pull together the scattered resources, some belonging to the network and some not, to create communications sessions that might invoke a multiplicity of connections and computer applications.　　它将协调与客户应用密切相关的人机交互作用，并将分散的资源集中在一起。这些资源有些属于网络，有些则不是，这就可以建立进行多种连接和计算机应用的通信业务了。　　· 本句为一长句，其主句为It will mediate…，and pull…，to create…。 　　[2]? Not only are voice and data given equal billing in ISDN and associated with a single subscriber address, but they may be tightly integrated, as in voice annotation of text and graphics or in “videotex videos” with synchronized animation and music.　　ISDN不仅对话音和数据进行相同计价和赋予相同的用户地址，而且如同文本和图形中使用话音解释或用同步动画和音乐做的“可视图文电视”一样，它们必须紧紧地综合在一起。　　· Not only为开头的主谓语词序倒装形式，and associated…address与in ISDN并列。 　　[3]? The rapid evolution of LANs and metropolitan area network (MANs) to high speeds, efficient inter-working, and wider availability, together with advances in software control, is making possible most of the services currently envisioned as supported by ISDN and others beyond the capabilities of narrowband ISDN.　　局域网和城域网在向高速、高效互连和更广泛应用方面飞速发展，并且与先进的软件控制相结合，使当前大多数业务通过ISDN和窄带ISDN之外的其他技术的支持正在成为可能。　　· 本句的主句结构为The rapid evolution…，is making possible…。as supported by…为条件状语。 　　[4]? It is essential that ISDN, if it is to achieve the u