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V.90 Modems

V.90 Modems. Telephone Bandwidth is Limited (Chapter 4) Bandwidth limits speed Limits speed to about 35 kbps When you transmit , limited to 35 kbps. 35 kbps. V.90 Modems. Telephone Bandwidth is Limited Limits occur when you transmit in analog to the phone company

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V.90 Modems

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  1. V.90 Modems • Telephone Bandwidth is Limited (Chapter 4) • Bandwidth limits speed • Limits speed to about 35 kbps • When you transmit, limited to 35 kbps 35 kbps

  2. V.90 Modems • Telephone Bandwidth is Limited • Limits occur when you transmit in analog to the phone company • Analog-to-digital converter (ADC) at the telephone company limits you to about 35 kbps Telephone Network PC V.34 modem ADC 33.6 kbps

  3. V.90 Modems • Receive at 56 kbps • ISP connects with digital line to the Telco • Sends at 56 kbps • No analog-to-digital converter to limit speed Digital Link Telephone Network PC ISP 56 kbps modem DAC No ADC! 56 kbps

  4. V.90 Modems • Receive at 56 kbps • 56 kbps digital channels inside phone network • Only local loop is analog today • Trunk lines and switches support 56 kbps transmission Digital Switches and Trunk Lines Telephone Network PC ISP 56 kbps modem DAC 56 kbps

  5. V.90 Modems • Receive at 56 kbps • Telephone company transmits in analog to subscriber at 56 kbps • Digital to audio converter (DAC) does not limit speed to less than 56 kbps Digital Link Telephone Network PC ISP 56 kbps modem DAC 56 kbps

  6. V.90 Modem • Telephone Company Does Not Have to Do Anything Differently • ADCs and DACs are already in place for ordinary voice service • Lack of change in phone system allowed fast implementation Digital Link ADC Telephone Network PC ISP 56 kbps modem DAC

  7. V.90 Modem • ISP Does Have to Do Things Differently • Digital line to telephone network • Special equipment at ISP • Does not use a V.90 modem • If used V.90 modem, could only send at 33.6 kbps Digital Link Telephone Network PC ISP 56 kbps modem DAC No V.90 Modem!

  8. V.90 Modem • User Needs a V.90 Modem • Does not need a new phone line • Not all phone lines will work, but it is never worth the cost to install a new line for V.90 modems

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