综合测试二

模拟试卷一一、单项选择题（每题只有一个正确答案，每题1分，共10分）1. The switch, circuit switches, have no capability of ______ user’s data on their way to the destination.A. calling, storedB. called, storingC. to call, to storeD. be called, be stored2. The switching element is a computer a message processor, with processing and storage capabilities. Message travels independently and asynchronously, their own way from source to destination.A. be referred to as; findingB. referred to as, findingC. be referred to as, to findD. referred to, finding3. The telephone contains a transmitter and receiver for_______ back and forth analog voice and analog electrical signals.A. convert, inB. converting, betweenC. conversion, toD. converted, into4. The trunks are designed multiple voice-frequency circuits either FDM or synchronous TDM.A. carry, useB. carried, usedC. to carry, to useD. to carry, using5. Designers have found it convenient these nodes into a hierarchy or tree topology, five classes of switching centers or nodes.A. organization, consistB. organize, consistingC. to organize, consisting ofD. organizing, to consist6. The term ISDN was first defined within the CCITT in 1972. Itreferred to a network end-to-end digital connectivity ________a range of services.A. providing, forB. provision, toC. provided, withD. provide, into7. In fact, ISDN conceived a quarter of a century agoand is only now to reach maturity.A. is, beginB. was, beginningC. be, to beginD. will be, began8. As regards economy, early studies suggested that digital services _______significant advantages since a substantial quantity of interface equipment in the telephone exchange could .A. offered, be eliminatedB. offer, eliminateC. offers, is eliminatedD. to offer, to eliminate9. The enhanced quality is achieved when a signal is digitally encoded degradation the transmission medium.A. overcome, toB. overcame, withC. overcoming, overD. to overcome, due to10. Similarly, the introduction of voice encoding techniques_______ pulse code modulation contributed the ISDN’s concept evolution.A. usage, onB. using, toC. use, withD. used, so as to二、英译汉短语（每题1分，共15分）1. the capability of storing or manipulating user’s data2. the information regarding the source and destination addresses3. the overall transmission delay of the message4. packet switching5. transmission unit6. low channel utilization7. the switching nodes called tandem switches8. architectural components9. full duplex10. multiple voice-frequency circuits11. isolated subnetworks12. two subscribers attached to different end offices13. degradation due to the transmission medium14. digital communication15.public communication carriers16. bandwidth limitations17.basic access signaling rate三、汉译英短语（每题1分，共15分）1、电路交换.2、双绞线3、存储转发方式4、交换技术5、信息转换6、公众电信网7、本地环路8、收费中心9、中间交换节点10、拓扑11、灵活性12、综合业务数字网13、接口设备14、语音编码15、基本接入四、阅读理解（每题2分，共20分），根据文章内容判断（√）（X）PASSAGE ONEBy far the largest circuit-switched network is the public telecommunications network—the telephone network. This is actually a collection of national networks interconnected to form an international service. Although originally designed and implemented to service analog telephone subscribers, it handles substantial data traffic via modem, and is gradually being converted to a digital network.The public telecommunication network, as with any communications network, can be described using four generic architectural components.·Stations: generally denoted as subscribers, these are the devices that attach to the network.·Interfaces:the interface between the stations and the network, referred to in the phone system as the local loop.·Nodes: the switching centers in the network.·Links: the branches between nodes, referred to as trunks.Most of the subscribers on the network are telephones. The telephone contains a transmitter and receiver for converting back and forth between analog voice and analog electrical signals. With the introduction of the digital data system, some subscribers that transmit digital signals have been incorporated into the network.The local loop is a pair of wires, generally twisted pair, That connects a subscriber to one of the nodes in the network. The local loop generally covers a distance of a few kilometers to a few tens of kilometers at most.1) The largest circuit-switched network is referred to as the public telecommunications network-the telephone network.( )2) The telephone network originally designed and implemented toserve a digital network. ( )3) We can describe the public telecommunications network with Stations, Nodes and Links. ( )4) The telephone only contains a receiver for converting back and forth between analog voice and anolog electrical signals. ( )5) The local loop is a pair of wires, generally twisted pair, that connects a subscriber to one of the nodes in the network . ( )6) The local loop generally covers a distance of a few meters to a few kilometers. ( )PASSAGE TWOThe term ISDN was first defined within the CCITT in 1972. It referred to a network providing end-to-end digital connectivity for a range of services. It also used the idea of a totally open network with universally available and standardized “ports”that can plug in everywhere. The concept has since then evolved from the existing telephone networks of countries undergoing changes due to the introduction of totally new digital technology in the switching and transmission equipment. Similarly, the introduction of voice encoding techniques using pulse code modulation contributed to the concept’s evolution. Initially, voice encoding was based upon a 64 kbit/s transmission rate. Today two 64 kbit/s, or 2B-channels coupled with a basic access signaling rate of 16 kbit/s, that is, the D-channel, constitute the essential ISDN transmission rate of 144 kbit/s. Currently PSTN, available in almost 200 countries and territories around the world, offers universal voice access to almost 750 million telephones around the world. ISDN is the network which will progressively provide a similar universal access for not only voice but data, facsimile, video, text, and other services as well.In the industrialized countries, the evolutionary nature of the ISDN concept has been a matter of economic practicality considering the vast telephone infrastructure already in place. The primary emphasis, however,has been the enhancement of the services rather than a single replacement of the services rather than a single replacement of existing equipment. This evolutionary approach has also merit for most of the developing countries, although in some instances where analog facilities do not exist presently or where they are very limited, the direct installation of digital facilities could allow a direct leapfrog to ISDN capabilities.Many planners believe that the transition form experimental ISDN technology to operational system will be convincingly made in the next few years. Certainly the 1990s will be the time of rapid operational growth. If true, a lot of issues will have to be resolved in coming months rather than in coming years . The current study period of the CCITT (1989～1992) will, of necessity, resolve virtually all standards issues on ISDN including even wideband ISDN for transmission rates up to 155 Mbit/s.ISDN is not a four-letter work. It is a blueprint to the electronic communications system of the future.7) The term ISDN was first defined with the CCITT in 1982. ( )8) ISDN referred to a network providing end-to-end digital connectivity for a range of services. ( )9) Today two 64 kbit/s, or 2 B-channels coupled with a basic access signaling rate of 16 kbit/s, that is ,the D-channel, constitute the essential ISDN transmission rate of 144 kbit/s (2B+D).( )10) ISDN is the network which will progressively provide a similar universal access for only voice, facsimile and video. ( )11) ISDN is a blueprint to the electronic communications system of the future. ( )12) The author thinks that a lot of issues on ISDN will have to be resolved in a few months. ( )五、英译汉短文（每题10分，共40分）1. Each subscriber connects via local loop to a switching center, known as an end office. Typically, an end office will support many thousands ofsubscribers in a localized area. There are over 19,000 end offices in the United States, so it is clearly impractical for each end office to have a direct link to each end other office. Rather, intermediate switching nodes are used.2. By far the largest circuit-switched network is the public telecommunications network—the telephone network. This is actually a collection of national networks interconnected to form an international service. Although originally designed and implemented to service analog telephone subscribers, it handles substantial data traffic via modem, and is gradually being converted to a digital network.3. The local loop is a pair of wires, generally twisted pair, that connects a subscriber to one of the nodes in the network. The local loop generally covers a distance of a few kilometers to a few tens kilometers at most.A two wire connection is inherently half-duplex; that is, it can carry voice in one direction at a time only. Similarly, it can carry digital signals in one direction at a time only. For full-duplex DDS connections, two twisted-pair links are generally used.4. In the industrialized countries, the evolutionary nature of the ISDN concept has been a matter of economic practicality considering the vast telephone infrastructure already in place. The primary emphasis, however, has been the enhancement of the services rather than a single replacement of the services rather than a single replacement of existing equipment. This evolutionary approach has also merit for most of the developing countries, although in some instances where analog facilities do not exist presently or where they are very limited, the direct installation of digital facilities could allow a direct leapfrog to ISDN capabilities.。