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Modem Standards

Modem Standards. Two Modems Must Follow Same Standards Speed standards (modulation method) Error correction and compression standards Facsimile standards Modern modem standards are created by the ITU-T. Modem Standards. Training Period

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Modem Standards

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  1. Modem Standards • Two Modems Must Follow Same Standards • Speed standards (modulation method) • Error correction and compression standards • Facsimile standards • Modern modem standards are created by the ITU-T

  2. Modem Standards • Training Period • When two modems first start talking, they negotiate standards to use; settle on highest common standards

  3. Modem Speed Standards (ITU-T) • V.90 • Receive at 56 kbps but send at only 33.6 kbps • Not all phone lines, ISPs support 56 kbps • Fall back to 33.6 kbps if cannot support • V.34 • 33.6 kbps send and receive • V.32 bis • 14.4 kbps send and receive • bis means second (version of the standard)

  4. Modem Standards: Error Correction and Compression • ITU-T • V.42: Error detection and correction • V.42 bis:Compression (up to 4:1) • Most newer modems have both • MNP Level 5 • Proprietary standard of Microcom • Once widely used • Provides both error correction and compression • Now largely superceded by V.42 and V.42 bis New

  5. Modem Standards • Facsimile Modem Standards • Most modems also act as fax modems • Facsimile requires different modulation than data transmission • V.14: 14.4 kbps • V.29: 9.6 kbps

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