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Essential Guide to Modems: Types, Standards, and Interface Protocols

Explore the types of modems including internal, external, and modem pools, with a focus on traditional and high-speed interface standards and protocols. Learn about connection negotiation, compression, security features, and more for efficient data transmission. Discover how modems connect multiple workstations and external users to networks, and delve into terminal-to-mainframe computer connections.

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Essential Guide to Modems: Types, Standards, and Interface Protocols

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  1. Chapter 4Making Connections

  2. Modem • Modulates digital data onto analog signal and then demodulate analog signal back to digital data • Features: • Standard telephone operations (auto-dial, etc.) • Connection negotiation (fallback and forward) • Compression and error correction • Fax • Security • Self-testing (loop-back – local, remote)

  3. Types of Modems • Internal • External

  4. Types of Modems • Modems for Laptops • PCMCIA cards • PC Cards • Cardbus (32bit PC card)

  5. Types of Modems

  6. Modem Pools • Multiple workstations sharing a modem. • External users to dial into a business or corporate network

  7. Traditional Interface Standards • Specified the interface between a DTE and DCE • EIA-232F • RS-232m • RS-449 • X.21 • Bell Interface Standards • Hayes

  8. High-speed Interface Protocols • FireWire • A bus that connects peripheral devices such as wireless modems and high-speed digital video cameras to microcomputers, at 400 Mbps. • Designated as IEEE 1394. • asynchronous connections • isochronous connections (provides a guaranteed data transport at a pre-determined rate

  9. High-speed Interface Protocols • Universal Serial Bus (USB) • Modern standard for interconnecting modems and other peripheral devices to microcomputers. • Plug and play • Power provided by the USB cable • High-speed connection (USB 1.0 is only 12Mbps, but USB 2.0 is 480 Mbps

  10. Asynchronous Connections • Data link layer. • Unit: frame • Start bit • Stop bit • Parity bit to detect errors

  11. Synchronous Connections • Data link layer • A large package (frame) • header and trailer flags • control information • optional address information • error detection code (checksum) • data.

  12. Terminal-to-Mainframe Computer Connections • A point-to-point connection is a direct, unshared connection between a terminal and a mainframe computer. • A multipoint connection is a shared connection between multiple terminals and a mainframe computer. • The mainframe is called the primary, and each terminal is called a secondary.

  13. Connections in Action

  14. Connections in Action • 1 and 2 - DIN connectors for keyboard and mouse • 3 USB connectors • 4 and 6 - DB-9 connectors, Serial-port • 5 Parallel port connector DB-25 (Centronics) (USB someday?) • 7, 8 and 9 - audio connectors

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