This is the Self-test in Chapter 12: Data Communications from the book COMMUNICATIONS ELECTRONICS by Louis E. Frenzel. If you are looking for a reviewer in Communications Engineering this will definitely help. I can assure you that this will be a great help in reviewing the book in preparation for your Board Exam. Make sure to familiarize each and every questions to increase the chance of passing the ECE Board Exam.
Start Practice Exam Test Questions
Direction: Either Supply the missing word(s) in each statement or Choose the letter that best answers each question.
1. Data communications is the transmission of _____ information.
2. True or false. Audio and video signals may be transmitted using data communications techniques.
3. The earliest form of data communications was the _____.
4. The earliest form of radio data communications is known as _____.
5. The Morse code is made up of combinations of _____ and _____ to represent characters.
6. Give the Morse code for the following characters (see Fig. 12-2): K, 8, ,. (page 310-Frenzel)
7. The 5-bit code used in teletype systems is called the _____ code.
8. A system of data communications using type writer like devices to send and receive coded messages is known as _____.
9. If in the Baudot code the character 11011 is sent and then the code 00111, the character _____ is received.
10. The most widely used binary data code is _____ which uses 7 bits to represent characters.
11. An 8-bit data code used in IBM systems is known as _____.
12. Write the ASCII codes for the following characters: B, 3, ?
13. What ASCII character is transmitted to ring a bell? BEL = _____.
14. The two types of data transmission are _____.
15. True or false. Serial data transfers are faster than parallel transfers.
16. The digital circuit often used to perform parallel-to-serial and serial-to-parallel data conversions is the _____
17. In asynchronous transmissions, _____ and _____ bits are used to signal the beginning and end of a character.
18. The speed of a serial data transmission is usually expressed in _____.
19. The number of symbols occurring per second in a data transmission is called the _____.
20. True or false. There can be more than i bit per baud in data transmissions.
21. True or false. Asynchronous transmission is faster than synchronous transmission.
22. In synchronous data transmission, data is sent in _____ of characters with special codes to signal the beginning and end.
23. In serial data transmission, a binary 0 is called a(n) _____ and a binary 1 is called a(n) _____.
24. The study of efficient information transfer is known as _____.
25. The amount of information transmitted is proportional to the system _____ and the _____ allowed for transmission.
26. The channel capacity of a 5-kHz bandwidth binary system is _____ bits/s assuming no noise.
27. If an 8-level encoding scheme is used in a 100 kHz bandwidth system, the channel capacity is _____ bits/s.
28. True or false. Multilevel or multi-symbol binary encoding schemes permit more data to be transmitted in less time, assuming a constant symbol interval.
29. By using a multi-symbol encoding scheme, a higher bit rate can’ be achieved with _____ (more, less) bandwidth.
30. The channel capacity of a 6-MHz channel with an SIN ratio of 25 dB is _____ Mbits/s.
31. The minimum allowable bandwidth for a binary signal with a bit rate of 200 kbits/s is _____ kHz.
32. A modem contains both _____ and _____ circuits.
33. Modems convert _____ signals to _____ signals and vice versa.
34. The transmission medium most widely used with modems is the _____.
35. Modems are the interface between _____.
36. _____ modulation is used in low speed modems.
37. In FSK, binary 0 and I levels are represented by different _____.
38. In an FSKs modem, a high frequency represents a(n) _____ and a low frequency represents a(n) _____.
39. The typical frequencies used in a full duplex FSK modem are as follows:
- originate 0 _____ Hz and 1 _____ Hz;
- answer 0 _____ Hz and 1 _____ Hz.
40. The IC used to perform serial-to-parallel and parallel-to-serial conversions and other operations in a modem is known as a(n) _____.
41. The modulation method that represents bits as different phase shifts of a carrier is known as _____.
42. In BPSK, phase shifts of _____ degrees and _____ degrees used to represent bifary 0 and binary 1, respectively.
43. The circuit used to produce BPSK is a(n) _____.
44. The circuit-used to demodulate BPSK is a(n) _____.
45. A(n) _____ circuit is used to generate the carrier to be used in demodulating a BPSK signal.
46. A carrier recovery circuit is not needed with _____ PSK modulation.
47. The key circuit used in a DPSK modulator is the _____.
48. The number of different phase shifts used in QPSK is _____.
49. In QPSK, how many bits are represented by each phase shift?
50. The number of bits represented by each phase shift in 16-PSK is _____.
51. The circuit used to create a dibit is known as a(n) _____.
52. A circuit that converts a 2-bit binary code into one of four dc voltage levels is known as a _____.
53. Quadrature amplitude modulation is a combination of _____ modulation and _____ modulation.
54. True or false. Modems must transmit signals in the 300-Hz to 3-kHz range.
55. True or false. Carrier recovery is not required in a QPSK demodulator.
56. True or false. When QPSK is used, the bit rate is faster than the baud (symbol) rate.
57. True or false. Each phase and/or amplitude change can represent only one bit.
58. True or false. With QAM, a 9600 bits/s signal can be transmitted within a 3000-Hz bandwidth.
59. Rules and procedures that describe how data will be transmitted and received are referred to as _____.
60. List five methods of error detection and correction.
61. The process of exchanging signals between transmitter and receiver to indicate status or availability is called _____.
62. A popular protocol used in personal computer data communications is known as _____.
63. A string of characters making up a message or part of a message is referred to as a(n) _____ of data.
64. Stop and start bits are used with, _____ (asynchronous, synchronous) data.
65. Synchronous protocols usually begin with the _____ character.
66. The characters that indicate message number, destination, or other facts are collectively referred to as the _____.
67. The _____ character designates the beginning of a message, while the character _____ indicates its end.
68. One simple but time-consuming way to ensure an error-free transmission is to send the data multiple times. This is called _____.
69. One type of special self checking error code is the _____ code.
70. Errors in data transmission are usually caused by _____.
71. The ratio of the number of bit errors to the total number of bits transmitted is known as the _____.
72. A bit added to the transmitted character to help indicate an error is called the _____ bit.
73. A number added to the end of a data block to assist in detecting errors is known as the _____
74. Write the correct parity bits for each number.
- a. Odd: 0011000 _____
- b. Even: 1111101 _____
- c. Odd: 0101101 _____
- d. Even: 1000110 _____
75. Another name for parity is _____.
76. The basic building block of a parity generator circuit is the _____ gate.
77. Performing an exclusive OR on corresponding bits in successive data words produces a(n) word.
78. An error-detection system that uses a BCC at the end of a block is known as a(n) _____.
79. Dividing the data block by a constant produces a quotient that is discarded and a remainder called the _____ character.
80. The CRC circuit is basically a(n) _____.
81. True or false. If a bit error cart be identified, it can be corrected.
82. The telephone system is an example of a _____.
83. True or false. A cable TV system is considered a network.
84. Most networks re smaller and cover shorter distances and are referred to as _____.
85. The acronym PBX means _____.
86. True or false. PBXs cannot be used with digital data.
87. The three main types of LAN topologies are _____.
88. A PBX is a type of _____ topology LAN.
89. An LAN that uses a central controller for multiple stations is the _____ topology.
90. One type of LAN connects multiple terminals and PCs to a large central _____ computer.
91. A LAN in which the message is passed from one station to the next until the destination is reached is called a(n) _____.
92. The stations or users in a network are referred to as _____.
93. A network in which all stations attach to a common cable is called a(n) _____.
94. 94: The fastest network configuration is the _____.
95. In a(n) _____ LAN configuration, if one station fails, the whole system fails.
96. A connection from a LAN to a mainframe computer is known as a(n) _____.
97. A connection from one LAN to another is called a(n), _____.
98. The three transmission media used in LANs are _____.
99. An extended variation of the bus topology is called the _____.
100. List the three main disadvantages of twisted pair cable.
101. _____ is the most widely used medium in LANs.
102. The medium that permits the highest data rates is _____.
103. The longest transmission distances can be achieved with _____ medium.
104. Give the average maximum data rates in Mbits/s for each medium: twisted pair, coax, fiber-optic cable.
105. The digital, voice, or video voltages are referred to as _____ signals.
106. When the basic data signal is sent directly over the medium, the type of operation is said to be _____.
107. _____ operation uses modulation techniques and FDM techniques to increase speed and the number of operational channels.
108. Broadband operation requires the use of a(n) _____ at each node.
109. Spread spectrum is both a _____ and a _____ technique.
110. The two main types of spread spectrum are _____ and _____.
111. In a frequency-hopping SS system, a _____ circuit generates the transmitter frequency.
112. In a frequency-hopping SS system, a _____ circuit selects the frequency produced by the synthesizer.
113. True or false. The hop rate is slower than the bit rate of the digital data.
114. To a narrowband receiver, an SS signal appears as a type of _____.
115. Two or more stations using SS and sharing a common band are identified and distinguished from one another by their unique _____.
116. The length of time a frequency-hopping SS transmitter stays on one frequency is called the _____.
117. In a direct-sequence SS transmitter, the data signal is mixed with a PSN signal in an _____ circuit.
118. True or false. In a direct-sequence SS system, the chip rate is faster than the data rate.
119. The type of modulation used with direct sequence SS is usually _____.
120. The most difficult part of SS communications is initiating and maintaining _____ prior to and during transmission.
121. The process of comparing one direct sequence SS signal to another in an effort to obtain a match is called _____.
122. The two main benefits of SS are _____ and _____.
123. The main circuit used in making a PSN code generator is a _____.
124. The frequencies allocated to spread spectrum by the FCC for civilian applications are _____, _____, and _____ MHz.
125. Two growing applications for SS are _____ and _____.