单项测试一

专项训练一

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UNIT 11

1. The switch, circuit switches, have no capability of

______user’s data on their way to the destination.

A. calling, stored

B. called, storing

C. to call, to store

D. be called, be stored

2. The circuit is set up by a special signaling message _____finds its way through the network,_____ channels in the path as it proceeds.

A. that, seizing

B. where, seizing

C. who, seized

D. one, be seized

3. 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. to call, find

B. calling, found

C. referred to as, finding

D. be called, sending

4. A variation of message switching is packet switching. Here the message is broken up into several pieces of a______ maximum length, packets.

A. given, called

B. give, call

C. giving, calling

D. to give, to call

5. In packet switching the message is into several pieces of a maximum length, called packets.

A. broken away

B. broken out

C. broken off

D. broken up

6. It is cost-effective only in those situations_____ once the circuit is set up there is a guaranteed steady flow of information transfer to amortize the initial cost.

A. which

B. where

C. that

D. when

7. In circuit switching, a total path of lines is set up from the origin to the destination at the time the

call .

A. connected; is made

B. connecting; is made

C. connected; makes

D. connecting; makes

8. Once the path , a return signal informs the source transmission.

A. is established; to begin

B. established; to begin

C. is established; beginning

D. established; beginning

9. In addition to the text , a message comprises a header and a checksum..

A. to transmit

B. transmitted

C. transmitting

D. to be transmitted

10. Messages travel independently and asynchronously,____ their own way from source to destination.

A. to find

B. find

C. found

D. finding

11. First the message is transmitted from the host to the message processor it is attached.

A. that

B. which

C. to that

D. to which

12. If a fixed dedicated end to end circuit were______ connecting the end users, then one must assign enough transmission bandwidth to the circuit meet the delay constraint with the consequence that the resulting channel utilization is low.

A. to set up; so as to

B. to be set up; in order to

C. setting up; so as to

D. to be setting up; in order to

13. If the circuit of high bandwidth were set up and released at each message transmission request, then the set up time would be large to the transmission time of the message.

A. compare

B. compared

C. comparing

D. to compare

14. This transmission technique the store-and-forward transmission technique.

A. also referred to as

B. is also referred to as

C. also referred to

D. is also referred to

UNIT 13

15. The telephone contains a transmitter and receiver for_____

back and forth analog voice and analog electrical signals.

A. convert, in

B. converting, between

C. conversion, to

D. converted, into

16. Each subscriber connects local loop to a switching center, as an end office.

A. to, calling

B. with, known

C. the, know

D. via, known

17. The trunks are designed multiple voice-frequency circuits either FDM or synchronous TDM.

A. carry, use

B. carried, used

C. to carry, to use

D. to carry, using

18. Although originally designed _____to service analog telephone subscribers, the telephone network handles substantial data traffic modem, and gradually being converted to a digital network..

A. implemented, via

B. implementing, in

C. to implement, within

D. design, on

19. Designers have found it convenient these nodes into a hierarchy or tree topology, five classes of switching centers or nodes.

A. organization, consist

B. organize, consisting

C. to organize, consisting of

D. organizing, to consist

20.There are over 19000 end offices in the United States, so it is clearly impractical each end office a direct link to each other end office.

A. of; having

B. of; to have

C. for; having

D. for; to have

21. Subscribers connect directly to end office,_____ must perform the same function a PBX.

A. that; and

B. which; as

C. which; and

D. that; as

22. The remaining centers simply serve the function of_____

traffic reduce transmission facility requirements.

A. concentrate; and

B. concentrating; to

C. being concentrated; to

D. concentrated; and

23. The routing algorithm is by seven-or ten-digit telephone number, uniquely identifies a subscriber and centers in its direct hierarchy.

A. drove; which

B. driven; that

C. drove; that

D. driven; which

24. Consider again two subscribers to different end offices.

A. attached

B. attaching

C. attach

D. to attach

25. High-usage trunks are direct connection between switching centers high volumes of internode traffic.

A. using for; for

B. used for; with

C. used to; for

D. being used; with

26. If the two subscribers are the aegis of different regional centers, the circuit will a trunk between regional centers, for a total of nine trunks in the path between the subscribers.

A. under; involve

B. in; involve

C. under; attach to

D. in; attach to

27. Generally, this link has lower capacity than the total number of PBX subscribers, the fact that, at any given time, only a fraction of the subscribers will external calls.

A. reflect; be engaged in

B. reflected; engage in

C. reflecting; be engaged in

D. to reflect; be engaging in

28. In addition to the five classes of switching centers_____ above, the network is augmented with additional switching nodes__ tandem switches.

A. listing; called

B. listed; calling

C. listing; to call

D. listed; called

29. With the introduction of the digital data system, some subscribers transmit digital signals into

the network.

A. that; have been incorporated

B. which; have incorporated

C. to; have been incorporated

D. for; have incorporated

UNIT 14

30. ISDN’s enormous importance is only gradually being .Y ears of work have been by the CCITT and the ISO.

A. understand, carry

B. understanded, carried

C. to be understood, to carry

D. understood, carried out

31. The term ISDN was first defined within the CCITT in 1972. It referred to a network end-to-end digital connectivity____ a range of services.

A. providing, for

B. provision, to

C. provided, with

D. provide, into

32. Similarly, the introduction of voice encoding techniques____ pulse code modulation contributed the ISDN’s concept evolution.

A. usage, on

B. using, to

C. use, with

D. used, so as to

33. In fact, ISDN conceived a quarter of a century

ago and is only now to reach maturity.

A. is, begin

B. was, beginning

C. be, to begin

D. will be, began

34. The enhanced quality is achieved when a signal is digitally encoded degradation the transmission medium.

A. overcome, to

B. overcame, with

C. overcoming, over

D. to overcome, due to

35. 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 eliminated

B. offer, eliminate

C. offers, is eliminated

D. to offer, to eliminate

36. The standards and system architecture of ISDN will largely____ the shape and form of global communications in the 21st century.

A. construct

B. lead

C. instruct

D. dictate

37. In fact, ISDN was a quarter of a century ago and is only now beginning to reach maturity.

A. constructed

B. concealed

C. conducted

D. conceived

38. ISDN is, therefore a mega-telecommunication issue and , it is probably the world’s best trillion dollar secret.

A. as so; keeping

B. as such; kept

C. the case being such; keeping

D. such as; kept

39. The digital service of ISDN provides flexibility in the transmission of voice, data, video and other services with equal .

A. value

B. ease

C. force

D. quantity

40. Initially voice encoding a 64 kbit/s transmission rates.

A. was based upon

B. based upon

C. be based upon

D. is being based upon

41. AS it evolved, ISDN the spotlight.

A. has put into

B. has been put into

C. has put in

D. has been put in

42. The integrated services digital network (ISDN) is the road map the future for all forms of digital communications.

A. for

B. of

C. to

D. in