LAN Switching and Wireless

271. If the frequency spectrum of a signal has a bandwidth of 500 Hz with the highest frequency at 600 Hz, what should be the sampling rate, according to the Nyquist theorem?

  1. 200 samples/s
  2. 500 samples/s
  3. 1000 samples/s
  4. 1200 samples/s

Correct answer: (D)
1200 samples/s

272. If the Hamming distance between a dataword and the corresponding codeword is three, there are __________ bits in error.

  1. 3
  2. 4
  3. 5
  4. none of the above

Correct answer: (A)
3

273. If the maximum amplitude of a sine wave is 2 V, the minimum amplitude is _________ V.

  1. 2
  2. 1
  3. -2
  4. between -2 and 2

Correct answer: (B)
1

274. In _________ APS, there are normally two lines: one working line and one protection line. Both lines are active all the time.

  1. one-plus-one
  2. one-to-one
  3. one-to-many
  4. none of the above

Correct answer: (A)
one-plus-one

275. In _________ APS, there is one working line and one protection line. The data are normally sent on the working line until it fails.

  1. one-plus-one
  2. one-to-one
  3. one-to-many
  4. none of the above

Correct answer: (B)
one-to-one

276. In _________ APS, there is only one protection line for many working lines. When a failure occurs in one of the working lines, the protection line takes control until the failed line is repaired.

  1. one-plus-one
  2. one-to-one
  3. one-to-many
  4. none of the above

Correct answer: (C)
one-to-many

277. In _________ each station sends a frame whenever it has a frame to send.

  1. pure ALOHA
  2. slotted ALOHA
  3. both (a) and (b)
  4. neither (a) nor (b)

Correct answer: (A)
pure ALOHA

278. In _________ encoding, the duration of the bit is divided into two halves. The voltage remains at one level during the first half and moves to the other level in the second half. The transition at the middle of the bit provides synchronization.

  1. Manchester
  2. differential Manchester
  3. both (a) and (b)
  4. neither (a) nor (b)

Correct answer: (C)
both (a) and (b)

279. In _________ framing, there is no need for defining the boundaries of frames.

  1. fixed-size
  2. variable-size
  3. standard
  4. none of the above

Correct answer: (A)
fixed-size

280. In _________ framing, we need a delimiter (flag) to define the boundary of two frames.

  1. fixed-size
  2. variable-size
  3. standard
  4. none of the above

Correct answer: (B)
variable-size

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