CIS 677: First Exam
 
Mo, Apr 19, 1997, 50 minutes
Open Notes, Open Books
Circle the right answer for each problem
Points per answer: correct 2, incorrect 0, none 1

• Problem #1 The twisting in a twisted pair
  1. Adds flexibility to the wire
  2. Doubles the bandwidth of the wire
  3. Reduces the bit error rate
  4. Reduces the maximum length to 100 meters per segment between repeaters
• Problem #2 The bandwidth of a channel is
  1. The highest frequency assigned to the channel
  2. The lowest frequency assigned to the channel
  3. The range of frequencies assigned to the channel
  4. None of the above
• Problem #3 What is the input power to a line if the output power is 10 watts and the attenuation is 10 decibels.
  1. 1 watt
  2. 10 watts
  3. 100 watts
  4. None of the above
• Problem #4 What is the attenuation from point A to point C if the attenuation from point A to point B is 10 decibels, and from point B to point C is also 10 decibels.
  1. 10 decibels
  2. 20 decibels
  3. 100 decibels
  4. None of the above
• Problem #5 According to Nyquist Law the capacity increases by a factor of 2 when
  1. The bandwidth is decreased by a factor of 2
  2. The noise is decreased by a factor of 2
  3. The number of encoding levels is increased by a factor of 2
  4. The number of encoding levels is squared
• Problem #6 The distance terrestrial microwaves can travel depends on
  1. The curvature of the earth but not the height of the antenna
  2. The height of the antenna and the curvature of the earth
  3. The height of the antenna but not the curvature of the earth
  4. None of the above
• Problem #7 A modulation of a carrier wave g(t) = A sin (2ft + ) may change
  1. Any of the parameters A, f, and
  2. Only A
  3. Only
  4. Only f
• Problem #8 Simplex communication between two stations allows flow of data
  1. In both directions simultaneously
  2. In either direction, but only in one direction at a given time
  3. Only in one direction
  4. None of the above is correct
• Problem #9 Assume that the NRZ-L and NRZI encodings use identical voltage levels. For how many bits of the input `1100101010' the two encodings agree on their voltage level, if initially they are both at the lower level.
  1. 3 or less
  2. 5
  3. 7
  4. none of the above
• Problem #10 How many volt changes the string 00001111000011110000 implies for Manchester encoding.
  1. 32 or less
  2. 33
  3. 34
  4. 35 or more
• Problem #11 According to the Sampling Theorem a sample of 36,000 entries per second
  1. Is sufficient to reconstruct any signal
  2. Is sufficient to reconstruct any signal whose highest significant frequency is not greater than 24,000 Hz.
  3. Is sufficient to reconstruct any signal whose highest significant frequency is not smaller than 24,000 Hz.
  4. None of the above
• Problem #12 The staircase function offers improved approximation for delta modulation when
  1. The grid of the amplitude axis has a quantization that depends on the quantization of the time axis
  2. The grid of the amplitude axis has higher quantization
  3. The grid of the amplitude axis has smaller quantization
  4. None of the above