Quiz 2
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Polytechnic University of the Philippines College of Engineering Computer Engineering Department NDC Cmpd., Sta. Mesa Manila CMP510 Long Examination #2 NAME
YR.&SEC
SCORE
GENERAL INSTRUCTIONS: 1. Follow all instructions carefully. Failure to do so will warrant a substantial deduction from your final score. 2. Write everything in non-red ink. 3. Borrowing of pens, calculators, etc. is considered cheating. Any form of cheating will merit automatically a grade of 5.0 4. You are not allowed to leave your seat unless you are through with the exam. If you have any questions, just raise your hand and the instructor or proctor will attend to you shortly. 5. Talking to or looking at your seatmate (and his/her paper) is automatically considered as cheating which is subject to very serious sanctions as stipulated in the student handbook. 6. Strictly, no erasures or alerations. GOOD LUCK!!!
I. MULTIPLE CHOICE (Score X4) Choose the letter that corresponds to your best answer. Write you answers (all in upper-case letters only) before each numbers. Show your complete solutions for questions that requires computation. NO SOLUTION, NO CREDIT POINTS EARNED.This is right minus wrong! No answers also means wrong! 1. The primary purpose of the stop bit or start bits is to: (A) stop or terminate the transmission of a character (B) to set the idle state of the transmission line to logic 1 (C) add to the overhead of asynchronous transmission (D) None of the above 2. . The Manchester or Biphase-L encoding form is used in the clock encoding and extraction implementation of synchronous transmission primarily because (A) it provides a more sophisticated way of encoding data (B) it is encoding method used in most hard disk system (C) it always provides a positive transition in the middle of each bit (D) None of the above 3. Which of the following statements is false? (A) Both timing and framing are necessary to maintain synchronization for proper decoding in data communications. Bit timing is accomplished by clocking the bits, Framing is usually accomplished by inserting special bits or control characters in data stream just for that purpose. (B) Digital transmission uses regenerative repeaters instead of amplifiers to correct the line signals (C) Repeaters regenerate digital pulses, removing any prior distortion. In comparison, amplifiers boost the strength of analog signals without increasing any prior distortion. (D) None of the above 4. If bit stuffing is applied to 1111011111011111100, then the transmissted bit stream is: (A) 111100111110111110100 (C) 111100111110011111100 (B) 111101111100111110100 (D) None of the choices 5. How many days will it take for a 600 bps system to transmit a 100 MB file using asynchronous transmission with 1 start bit and 1 stop bit? (A) 20 (C) 22 (B) 21 (D) 23 6. Synchronous transmission is more complicated but more efficient than asynchronous transmission. This statement is: (A) undoubtedly true
(B) false, synchronous transmission is simpler and more efficient than asynchronous transmission (C) false, synchronous transmission is simpler but less efficient than asynchronous transmission (D) false, synchronous transmission is more complicated and less efficient than asynchronous transmission 7. A 1MB file (encoded in standard ASCII) is transmitted using asynchronous transmission with 1 start bit and 1.5 stop bits. It uses a dta rate of 9,600 bps, then the percentage overhead will be: (A) 20.00% (C) 27.27% (B) 23.81% (D) 33.33% 8. Which transmission technique is primarily used when the data to be transmitted are generated at random interval? (A) parallel (C) asynchronous (B) serial (D) synchronous 9. If a 9,600 bps asynchronous system uses extended ASCII with 1 start and 1 stop bit, then the effective information rate will be: (A) 6, 981.81 bps (C) 7, 680.00 bps (B) 7, 314.28 bps (D) 9, 600.00 bps 10. How long it will take a 9, 600 bps digital system to transmit seven (7) consecutive bytes using asynchronous transmission with 1 start bit and 1.5 stop bits? Assume that each byte is encoded using standard ASCII. (A) 3.83 ms (C) 15.31 ms (B) 7.66 ms (D) 30.63 ms 11. If a 100MB file is transmitted using asynchronous transmission (using extended ASCII) with 1 start bit and 1 stop bit, then the total overhead will be: (A) 209, 715, 200 bits (C) 1, 048, 576, 000 bits (B) 838, 860, 800 bits (D) None of the choices 12. 12. If the transmitter clock in asynchronous transmission is too fast, then there is possibility that the receiver will not sample a bit. This statement is: (A) absolutely true (B) false, if the transmitter clock is too fast, then there is the possibility that the receiver will sample a bit more than once (C) false, if the receiver clock is too fast, then there is possibility that the receiver will not sample a bit (D) false, even if the receiver and transmitter clocks are 100% synchronized, there is always a possibility that a bit will not be sampled 13. A 10KB file (encoded in standard ASCII) is transmitted using asynchronous transmission with 1 start bit and 1.5 stop bit. It uses a data rate of 4, 800 bps, then the percentage overhead will be: (A) 20.00% (C) 27.27% (B) 23.81% (D) 33.33% 14. Approximately, how many hours will it take a 4,800 bps asynchronous system to transmit a 15MB file assuming that it uses 1 start bit and 2 stop bits. Assume that the file is encoded in standard ASCII. (A) 7 (C) 9 (B) 8 (D) 10 15. Which of the following is not an advantage of digital signals over analog signals? (A) It takes more electrical noise to corrupt digital signals than it does to contaminate an analog signal. (B) Most digital signal communication systems send specific and separate data that allows the receiver to detect errors. (C) Digital signals are faster than analog signals (D) None of the above 16. Which is the principla difference between asynchronous and synchronous transmission? (A) The file transfer protocols are different (B) The error detection mechanisms are different (C) The methods of synchronizing transmitter and receiver clocks are different (D) One is more expensive than the other 17. Which transmission technique is primarily used when the rate at which characters are generated is indeterminate?
(A) parallel (C) asynchronous (B) serial (D) synchronous 18. A 10 GB file (encoded in standard ASCII) is transmitted using asynchronous transmission with 1 start bit and 1.5 stop bits. If the data rate is 19, 200 bps, then the percentage overhead will be: (A) 20.00% (C) 27.27% (B) 23.81% (D) 33.33% 19. A synchronous transmission 2400bps modem has a higher information rate than an asynchronous 2400 bps modem because (A) the synchronous modem uses a clock for synchronization (B) the synchronous modem can detect bit errors (C) the synchronous modem is less prone to errors (D) the asynchronous modem must transmit a start and stop bit with each characters for synchronization 20. In spite of its advantages, synchronous transmission is not widely used in many communication networks because of its: (A) cost (C) inefficiency (B) complexity (D) high overhead 21. Mark and space refer to respectively to (A) dot and dash (C) binary 1 and binary 0 (B) message and interval (D) on and off 22. Start and stop bits, respective, are: (A) mark, space (C) space, space (B) space, mark (D) mark, mark 23. A synchronous transmission usually begins with which character? (A) SYN (C) SOH (B) STX (D) ETB 24. The characters making up the message in a synchronous trnsmission are collectively referred to as a data (A) set (C) block (B) sequence (D) collection 25. Which of the following is used to allow the receiver to identify error in the frame and requests for a retransmission of the frame? (A) BCC (C) SDLC (B) BSC (D) SSA THOUGHT: “Excellence is never an accident, it is achive through a hard work....”
YR.&SEC
SCORE
GENERAL INSTRUCTIONS: 1. Follow all instructions carefully. Failure to do so will warrant a substantial deduction from your final score. 2. Write everything in non-red ink. 3. Borrowing of pens, calculators, etc. is considered cheating. Any form of cheating will merit automatically a grade of 5.0 4. You are not allowed to leave your seat unless you are through with the exam. If you have any questions, just raise your hand and the instructor or proctor will attend to you shortly. 5. Talking to or looking at your seatmate (and his/her paper) is automatically considered as cheating which is subject to very serious sanctions as stipulated in the student handbook. 6. Strictly, no erasures or alerations. GOOD LUCK!!!
I. MULTIPLE CHOICE (Score X4) Choose the letter that corresponds to your best answer. Write you answers (all in upper-case letters only) before each numbers. Show your complete solutions for questions that requires computation. NO SOLUTION, NO CREDIT POINTS EARNED.This is right minus wrong! No answers also means wrong! 1. The primary purpose of the stop bit or start bits is to: (A) stop or terminate the transmission of a character (B) to set the idle state of the transmission line to logic 1 (C) add to the overhead of asynchronous transmission (D) None of the above 2. . The Manchester or Biphase-L encoding form is used in the clock encoding and extraction implementation of synchronous transmission primarily because (A) it provides a more sophisticated way of encoding data (B) it is encoding method used in most hard disk system (C) it always provides a positive transition in the middle of each bit (D) None of the above 3. Which of the following statements is false? (A) Both timing and framing are necessary to maintain synchronization for proper decoding in data communications. Bit timing is accomplished by clocking the bits, Framing is usually accomplished by inserting special bits or control characters in data stream just for that purpose. (B) Digital transmission uses regenerative repeaters instead of amplifiers to correct the line signals (C) Repeaters regenerate digital pulses, removing any prior distortion. In comparison, amplifiers boost the strength of analog signals without increasing any prior distortion. (D) None of the above 4. If bit stuffing is applied to 1111011111011111100, then the transmissted bit stream is: (A) 111100111110111110100 (C) 111100111110011111100 (B) 111101111100111110100 (D) None of the choices 5. How many days will it take for a 600 bps system to transmit a 100 MB file using asynchronous transmission with 1 start bit and 1 stop bit? (A) 20 (C) 22 (B) 21 (D) 23 6. Synchronous transmission is more complicated but more efficient than asynchronous transmission. This statement is: (A) undoubtedly true
(B) false, synchronous transmission is simpler and more efficient than asynchronous transmission (C) false, synchronous transmission is simpler but less efficient than asynchronous transmission (D) false, synchronous transmission is more complicated and less efficient than asynchronous transmission 7. A 1MB file (encoded in standard ASCII) is transmitted using asynchronous transmission with 1 start bit and 1.5 stop bits. It uses a dta rate of 9,600 bps, then the percentage overhead will be: (A) 20.00% (C) 27.27% (B) 23.81% (D) 33.33% 8. Which transmission technique is primarily used when the data to be transmitted are generated at random interval? (A) parallel (C) asynchronous (B) serial (D) synchronous 9. If a 9,600 bps asynchronous system uses extended ASCII with 1 start and 1 stop bit, then the effective information rate will be: (A) 6, 981.81 bps (C) 7, 680.00 bps (B) 7, 314.28 bps (D) 9, 600.00 bps 10. How long it will take a 9, 600 bps digital system to transmit seven (7) consecutive bytes using asynchronous transmission with 1 start bit and 1.5 stop bits? Assume that each byte is encoded using standard ASCII. (A) 3.83 ms (C) 15.31 ms (B) 7.66 ms (D) 30.63 ms 11. If a 100MB file is transmitted using asynchronous transmission (using extended ASCII) with 1 start bit and 1 stop bit, then the total overhead will be: (A) 209, 715, 200 bits (C) 1, 048, 576, 000 bits (B) 838, 860, 800 bits (D) None of the choices 12. 12. If the transmitter clock in asynchronous transmission is too fast, then there is possibility that the receiver will not sample a bit. This statement is: (A) absolutely true (B) false, if the transmitter clock is too fast, then there is the possibility that the receiver will sample a bit more than once (C) false, if the receiver clock is too fast, then there is possibility that the receiver will not sample a bit (D) false, even if the receiver and transmitter clocks are 100% synchronized, there is always a possibility that a bit will not be sampled 13. A 10KB file (encoded in standard ASCII) is transmitted using asynchronous transmission with 1 start bit and 1.5 stop bit. It uses a data rate of 4, 800 bps, then the percentage overhead will be: (A) 20.00% (C) 27.27% (B) 23.81% (D) 33.33% 14. Approximately, how many hours will it take a 4,800 bps asynchronous system to transmit a 15MB file assuming that it uses 1 start bit and 2 stop bits. Assume that the file is encoded in standard ASCII. (A) 7 (C) 9 (B) 8 (D) 10 15. Which of the following is not an advantage of digital signals over analog signals? (A) It takes more electrical noise to corrupt digital signals than it does to contaminate an analog signal. (B) Most digital signal communication systems send specific and separate data that allows the receiver to detect errors. (C) Digital signals are faster than analog signals (D) None of the above 16. Which is the principla difference between asynchronous and synchronous transmission? (A) The file transfer protocols are different (B) The error detection mechanisms are different (C) The methods of synchronizing transmitter and receiver clocks are different (D) One is more expensive than the other 17. Which transmission technique is primarily used when the rate at which characters are generated is indeterminate?
(A) parallel (C) asynchronous (B) serial (D) synchronous 18. A 10 GB file (encoded in standard ASCII) is transmitted using asynchronous transmission with 1 start bit and 1.5 stop bits. If the data rate is 19, 200 bps, then the percentage overhead will be: (A) 20.00% (C) 27.27% (B) 23.81% (D) 33.33% 19. A synchronous transmission 2400bps modem has a higher information rate than an asynchronous 2400 bps modem because (A) the synchronous modem uses a clock for synchronization (B) the synchronous modem can detect bit errors (C) the synchronous modem is less prone to errors (D) the asynchronous modem must transmit a start and stop bit with each characters for synchronization 20. In spite of its advantages, synchronous transmission is not widely used in many communication networks because of its: (A) cost (C) inefficiency (B) complexity (D) high overhead 21. Mark and space refer to respectively to (A) dot and dash (C) binary 1 and binary 0 (B) message and interval (D) on and off 22. Start and stop bits, respective, are: (A) mark, space (C) space, space (B) space, mark (D) mark, mark 23. A synchronous transmission usually begins with which character? (A) SYN (C) SOH (B) STX (D) ETB 24. The characters making up the message in a synchronous trnsmission are collectively referred to as a data (A) set (C) block (B) sequence (D) collection 25. Which of the following is used to allow the receiver to identify error in the frame and requests for a retransmission of the frame? (A) BCC (C) SDLC (B) BSC (D) SSA THOUGHT: “Excellence is never an accident, it is achive through a hard work....”
