V.90 and V.92 Modems

• Combines analog and digital transmission

• Uses a technique based on PCM concept

  • Recognizes PCM’s 8-bit digital symbols (one of 256 possible symbols) 8,000 per second
  • Results in a max of 56 Kbps data rate (1 bit used for control)

• V.90 Standard

  • Based on V.34+ for Upstream transmissions (PC to Switch)
  • Max. upstream rate is 33.4 Kbps

• V.92 Standard (most recent)

  • Uses PCM symbol recognition technique for both ways
  • Max. upstream rate is 48 kbps

• Very sensitive to noise ? lower rates

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