1. Chapter 4 Making 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)

4. Types of Modems Internal External

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

6. Types of Modems TypesFeatures 56K Digital Modem 56Kbps CSU/DSU ( for T1 digital telephone lines) Symmetric 1.544Mbps Cable Modem Asymmetric:  Download: 2.5Mbps  Upload: 350Kbps ISDN Modem 128Kbps all digital DSL Modem Speed similar to Cable Modem All digital

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

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

9. 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

10. 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 12 Mbps, but USB 2.0 is 480 Mbps

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

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

13. 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.

15. Connections in Action

16. 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