Week3TFMCTutorWord格式.docx

1、5. Digital transmission produces more errors than analog transmission.6. Newer telephone circuits, built during the last decade, offer higher quality because they were built using analog transmission.7. In a multipoint circuit configuration, each computer can use the circuit at the same time.8. In s

2、implex transmission, the data flows in both directions at the same time 9. An intercom is an example of half-duplex transmission.10. The amount of time it takes to switch between sending and receiving in half-duplex transmission is called the propagation delay.11. In full-duplex transmission, two st

3、ations can send and receive simultaneously. 12. Guided media refers to the type of media in which the message is broadcast through the air.13. Coaxial cable costs less and offers less shielding to electrical interference than twisted pair cable.14. Fiber optic cable carries signals in traditional el

4、ectrical form 15. Multimode fiber is capable of longer transmission distances than single mode fiber.16. Radio data transmission requires that each device has a radio receiver/transmitter and uses a specific frequency.17. Microwave transmissions require a line of sight between any two points. 18. Pr

5、opagation delay is negligible with satellite transmission. 19. One form of interference with satellite transmission is called raindrop attenuation in which the transmissions are absorbed by heavy rain.20. Fiber optic cable can only be used on LANs.21. Radio, infrared, microwave and satellite are all

6、 examples of guided media.22. Of all the media available, fiber optic provides the highest transmission speeds.23. Coding schemes are groups of bits that translate into the “alphabet” of any given system. 24. ASCII is the least popular code for data communications.25. The predominant method of trans

7、ferring information internally in a computer is via parallel mode. 26. Serial mode transmission is much faster than parallel mode transmission.27. Ethernet, a common LAN technology, uses Manchester encoding. 28. Digital transmission occurs when the signal sent over the transmission media constantly

8、varies among an infinite number of states. 29. Frequency is the number of cycles per second and is expressed in Hertz.30. Amplitude, frequency and phase are all characteristics of a sound wave.31. Frequency modulation refers to the changing of the height of the sound wave.32. Demodulation is the con

9、versation of an analog signal into a digital signal.33. “Handshaking” refers the testing of the circuit to determine the optimum combination of symbol rate and modulation technique that will produce the highest data transmission rates.34. Data compression can increase the throughput of a communicati

10、on link.35. A codec converts an incoming digital signal to an analog signal for transmission over an analog network.36. One way to reduce quantizing errors is to increase the sampling rate of the analog signal.37. The “local loop” refers to the wires that run from the customer premises to the teleph

11、one switch of the telephone company.38. Multiplexing increases the cost of provisioning network circuits. Moderate 39. Frequency division multiplexing divides the circuit into a set of different time slots.40. Time division multiplexing is more efficient that frequency division multiplexing because

12、the guardbands used in the frequency division multiplexing or not needed.41. Statistical time division multiplexing does not require the capacity of the circuit to be equal to the sum of the combined circuits. 42. Wavelength division multiplexing can only used with copper cables.MULTIPLE CHOICEData

13、is physically transmitted from one computer or terminal to another in the _ layer.a. physicalb. transportc. applicationd. terminale. data link A Difficulty: Easy _ refers to the transmission characteristics of the circuit.a. handshakingb. virtual circuitc. bondingd. logical circuite. physical circui

14、t D Difficulty:Two fundamentally different types of data are:a. DSL and ADSLb. asymmetric and symmetricc. Microsoft and IBM d. digital and analoge. local area and wide areaIn general, networks designed to transmit primarily computer data are likely to be _, while networks designed to transmit voice

15、data are likely to be _.a. slow, fastb. level 1, level 2c. numeric, musicald. direct, indirecte. digital, analog E Difficulty:A（n） _ circuit is another name for a multipoint configuration.a. analogb. dedicatedc. point-to-pointd. sharede. simplexWhich is not true about point-to-point circuits?a. poin

16、t-to-point circuits are dedicated to the use of the two computers.b. point-to-point circuits are more expensive than multipoint circuits.c. point-to-point circuits are called dedicated circuits.d. point-to-point circuits reduce the amount of cable required and use the circuit more efficiently than m

17、ultipoint circuits.e. Point-to-point circuits are used when the computers generate enough traffic to fill the capacity of the communication circuit.Having a conversation with someone using a cellular phone is an example of _ transmission.a. simplexb. full-duplexc. half-duplexd. analoge. digital B Di

18、fficulty:The ability to transmit in both directions, but only in one direction at a time is an example of _ transmission. C Difficulty:The two basic types of media are:a. statistical and frequencyb. guided and wireless （radiated）c. local and wide aread. attenuator and Gaussiane. duplexed and non-dup

19、lexedThe type of media usually installed on homes and businesses by the telephone company is called _.a. fiber optic cableb. coaxial cablec. twisted paird. phone cablee. phone wireThe earliest type of fiber optic systems were:a. Graded index multimodeb. Attenuatedc. Multimoded. Single modee. Step mo

20、deAnother term for the weakening of a signal over distance is:a. turnaround timeb. propagation delayc. dispersiond. insulatione. attenuation_ refers to the spreading of the signal that different parts of the signal arrive at different times at the destination.Which of the following media can best wi

21、thstand harsh environmental conditions?a. shielded twisted pair b. unshielded twisted pair c. Cat 5 twisted paird. coaxial cablee. fiber optic cableMicrowave transmission:a. is a type of high frequency radio communicationb. requires a clear line-of-sight pathc. is typically used for long distance da

22、ta transmissiond. does not require the laying of any cablee. all of the above_ refers to the time it takes for a signal to travel from sender to recipient （highly exaggerated with satellite transmission）.a. Line-of-sight effect b. Multimode indexc. Saturation effect d. Raindrop attenuatione. Propaga

23、tion delayWhich of the following is not an important factor to consider when selecting media to be used in a network?a. prestige value of the type of mediab. type of network c. costd. transmission distancee. securityWhich of the following media is the least secure?a. coaxial cableb. unshielded twisted pairc. shi