InterviewSolution

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51.	What is the minimum frequency of sampling so that the analog waveform is adequately expressed?(a) Minimum sampling rate(b) Minimum sampling frequency(c) Nyquist frequency(d) Conversion rateI had been asked this question by my school principal while I was bunking the class.This key question is from Data Conversion in chapter Digital Communication Techniques of Avionics
Answer» Right choice is (c) NYQUIST FREQUENCY For EXPLANATION: The MINIMUM frequency at which an analog wave should be sampled is given by Nyquist frequency. If the sampling frequency is below this limit then the analog waveform is not fully represented and leads to DATA loss.

52.	In parallel communication, if the time interval to transmit one bit is 10μs. What is the time to transmit an 8-bit word?(a) 10μs(b) 100μs(c) 0.1μs(d) 0.01μsThe question was posed to me in unit test.My query is from Parallel and Serial Transmission topic in section Digital Communication Techniques of Avionics
Answer» Right OPTION is (a) 10μs The best I can EXPLAIN: Since all the bits are transmitted SIMULTANEOUSLY, the time taken for the transmission of one bit is EQUAL to the time taken for the transmission of any NUMBER of bits. Therefore the time taken is 10μs.

53.	What is the main role of an ADC?(a) Amplify(b) Convert analog to digital(c) Reduce noise(d) Increase rangeThis question was posed to me in semester exam.Query is from Data Conversion in portion Digital Communication Techniques of Avionics
Answer» Correct ANSWER is (B) Convert analog to digital The best I can explain: ADC corresponds to Analog to Digital Converter which is USED to convert an analog SIGNAL into a digital. Digital signal can be processed and manipulated.

54.	The devices that convert serial to parallel and parallel to serial are called?(a) Serializer/Deserializer(b) Transmission converters(c) Multiplexer(d) PreemphasizerThis question was addressed to me in an internship interview.The query is from Parallel and Serial Transmission topic in section Digital Communication Techniques of Avionics
Answer» The correct option is (a) Serializer/Deserializer For explanation: Parallel transmission is high SPEED and serial data can cover LONGER distances. Hence they are USED INTERCHANGEABLY and the devices which convert serial to parallel and parallel to serial transmission is called serializer/deserializer device (SERDES).

55.	In serial communication, if the time interval to transmit one bit is 10μs. What is the time to transmit an 8-bit word?(a) 8μs(b) 80μs(c) 0.8μs(d) 0.008μsThe question was asked during an online exam.I would like to ask this question from Parallel and Serial Transmission topic in division Digital Communication Techniques of Avionics
Answer» Right option is (b) 80μs To explain: Total TRANSMISSION time = time for each BIT x total number of bits = 8 x 10μs = 80μs.

56.	Why higher speed communications in parallel transmission require shorter length?(a) Cost(b) Resistance(c) Inductive and capacitance effects(d) NoiseThis question was posed to me during a job interview.Question is taken from Parallel and Serial Transmission topic in section Digital Communication Techniques of Avionics
Answer» The correct option is (C) INDUCTIVE and capacitance effects Easiest explanation: As the SPEED of transmission or the frequency of transmission increases the wavelength of transmission BECOMES comparable with the length of the data bus. This causes inductive and capacitance effects which degrade the SIGNAL.

57.	Which bit is transmitted first in a serial communication?(a) Least significant bit(b) Most significant(c) All the bits simultaneously(d) Not in any specific orderThis question was addressed to me in an international level competition.The query is from Parallel and Serial Transmission topic in portion Digital Communication Techniques of Avionics
Answer» The correct choice is (a) Least SIGNIFICANT bit The explanation: In serial transmission, the BITS are transmitted one after the other in a SPECIFIC ORDER. The least significant bit is transmitted first and the most significant bit is transmitted in the end.

58.	Which of the following is a false reason for parallel lines not being used for long distances?(a) Cost factor(b) Signal Attenuation(c) Number of transmission channels(d) Low speedI had been asked this question in an interview for job.Enquiry is from Parallel and Serial Transmission in portion Digital Communication Techniques of Avionics
Answer» Correct answer is (d) Low speed For EXPLANATION I would say: One of the major DISADVANTAGES of USING parallel transmission for long distance is that laying the data bus is costly. To cover a distance of 10km for an 8 bit system, we need a cable of 80km LENGTH. Parallel data are usually faster than serial since all the bits are transmitted simultaneously.

59.	What is the cable that carries the information in parallel transmission called?(a) Parallel line(b) Data bus(c) Data line(d) Data linkThe question was posed to me by my college professor while I was bunking the class.My doubt is from Parallel and Serial Transmission in section Digital Communication Techniques of Avionics
Answer» The correct ANSWER is (b) DATA bus Explanation: In a parallel transmission multiwire CABLES are used. These cables CARRY a BIT in each wire and are referred as data bus.

60.	Why can Digital data use time division multiplexing?(a) Less power(b) High power(c) Discrete data(d) Continuous dataThis question was posed to me during an interview for a job.Query is from Digital Transmission of Data topic in division Digital Communication Techniques of Avionics
Answer» The correct answer is (c) Discrete data Easy explanation: DIGITAL data is discrete and hence can be transmitted VIA time division multiplexing, whereas analog data is continuous and can only be transmitted as a whole. However, analog data can be converted into digital by analog to digital converters and then be transmitted via time division multiplexing. Time division multiplexing is one of the BIGGEST advantages of digital communication.

61.	Speed of transmission is increased by channel encoding.(a) True(b) FalseThe question was posed to me in my homework.This question is from Digital Transmission of Data topic in section Digital Communication Techniques of Avionics
Answer» Correct answer is (b) False The explanation: Speed of transmission is REDUCED when data is channel encoded. For example, to transmit 1 BYTE of data, the encoding process may add 3 extra BITS for a total of 11 bits. If the bit time is 100 ns, then it takes 800 ns to send the data bits but 1100 ns to send the encoded data.

62.	In a parallel communication, each bit requires a transmitter and receiver.(a) True(b) FalseI have been asked this question by my college professor while I was bunking the class.My question is taken from Parallel and Serial Transmission topic in section Digital Communication Techniques of Avionics
Answer» The CORRECT answer is (a) True The BEST I can explain: In a parallel transmission each bit is transmitted in a separate WIRE. SINCE each bit is transmitted individually, each bit requires a separate transmitter and a RECEIVER.

63.	Data is transmitted in512 bytes. What is the average number of errors expected if the system BER is 2:10,000?(a) 1(b) 0(c) 0.542(d) 0.819This question was addressed to me in a job interview.I want to ask this question from Digital Transmission of Data topic in section Digital Communication Techniques of Avionics
Answer» Right option is (d) 0.819 The best I can EXPLAIN: TOTAL NUMBER of bits = 512 X 8 = 4096 bits Average number of errors = (2/10,000) x 4096 = 0.819.

64.	What is the number of error bits that occur for a given number of bits transmitted called?(a) Bit error(b) Error rate(c) Bit error rate(d) Error bit rateI had been asked this question in unit test.My question is taken from Digital Transmission of Data topic in section Digital Communication Techniques of Avionics
Answer» Right choice is (C) Bit error rate Explanation: Bit rate error(BER) is the number of error bits that are present for a GIVEN number of bits transmitted. It depends on several factors like the environment, equipment and other CONSIDERATIONS. BER is calculated for a particular set of conditions.

65.	What is the process of digital communication where a threshold value is set at the receiver to reduce noise?(a) Signal threshold(b) Data regeneration(c) Signal regeneration(d) Signal cut offThis question was addressed to me in an online interview.The origin of the question is Digital Transmission of Data in division Digital Communication Techniques of Avionics
Answer» Correct answer is (c) Signal regeneration Explanation: In the process of signal regeneration a cut off value or threshold value is set in the RECEIVER so that the noise can be CLIPPED off. When the values are set properly only the binary data would PASS through the circuit. This produces a CLEAN output pulse.

66.	Why is digital data not easily affected by noise?(a) High power transmission(b) Cannot easily change binary 1 to 0(c) High frequency transmission(d) Low frequency transmissionI have been asked this question during an interview.My query is from Digital Transmission of Data topic in section Digital Communication Techniques of Avionics
Answer» CORRECT answer is (B) Cannot easily change BINARY 1 to 0 Best explanation: Noise is inevitable in a SIGNAL transmission. In a digital transmission the amplitude of the noise MUST be higher than the amplitude of the signal at binary ’1’, which is generally not the case, and vice versa. The receiver can differentiate between binary ‘1’ and ‘0’ with a significant amount of noise.

67.	Which of the following is false with respect to digital data transmission?(a) LAN is a digital data transmission(b) Can transmit binary data(c) Only restricted to communication between computers(d) Can transmit analog dataI have been asked this question in quiz.I need to ask this question from Digital Transmission of Data in division Digital Communication Techniques of Avionics
Answer» Right ANSWER is (c) Only restricted to communication between COMPUTERS Easiest EXPLANATION: Digital data communication was only restricted to communication between computers. Since analog signals can now be easily converted into digital signals USING analog to digital converter,digital TRANSMISSION can now transmit voice, video and other analog signals in digital form.