Telecommunications
& Networks.
* Communications Hardware
* Modulation Protocols
* Transmission Media
* Synchronous and Asynchronous
* ISDN
* Uses of Telecommunications
LANs, WANs, and Intranets

* Networks
* LAN s
* WANs
*  Intranets
Background 
* Early systems processed in batch
* Centralized system
* routine processing delays
* SO...Data Communication was born
Data Communication:
* Combination of computer and communications 
technologies
* Telephone system first choice
Networks
* Share hardware, software, and data resources
* LANS
* WANS
Local Area Networks
* Share hardware, software, and data resources
* Confined to one geographical area
* Hardware Components
* Network Cable
* Cable Interface Unit
* Network Interface Card (NIC)
* Gateways and Bridges
Network Topology
* Star
* Ring
* Modified Ring
* Bus
Star Topology
* Requires a host computer
* All messages are routed through the host
* Very Fast
* If the central computer fails, so does the network
Ring Topology
* All nodes are attached in a circle
* Messages travel around the ring until they reach the computer 
to which they are addressed
* If the ring is broken, the network could still work
* Slower than Star, but more RELIABLE
Modified Ring Topology
* All nodes are attached to all other nodes
* Messages travel through any combination until they reach the 
computer to which they are addressed
* Fast, Very Reliable, but EXPEN$IVE
Bus Topology
* Does not require a central or host computer
* Each node manages part of the network
* Information can be transmitted from one computer directly to 
another without traveling through every other node
* The most popular LAN topology
Wide Area Networks
* Spread over a large geographical area
* Physical Media
* Telephone Lines
* Fiber Optic Cables
* Microwaves
* Satellites
DATA COMMUNICATIONS
Problems:
* Drop in intensity
* noise 


Hardware 


* Analog Signals
* Digital Signals
* Demodulation
from analog to digital
* Modulation
from digital to analog 
* Modems - Internal/External/Fax/Modems
WAN Hardware
* Multiplexor
* Controller
* polling
* contention
* Concentrator
* Front-End Processor


Hardware
* Modulation Protocols
* Transmission Speed
* bps
* baud rate
* Bandwidth
* voice grade
* wideband
Wired Channels:
* Wired Transmission Media
* Twisted-Pair Cable
* 9600 bps
* Coaxial Cable
* 10-100 Mbps
* Fiber-optic Cable
* 5+ Gbps  * *
Wireless Channels-
* Wireless Transmission Media
* Terrestrial Microwave Transmission
* 100-200Mbps
* Satellite Microwave Transmission

Hardware
* Channels-Transmission Modes
* Synchronous Transmission
* Asynchronous Transmission

Hardware
* Digital Telephony
* Last-Mile Problem
* ISDN
* Digital Modems
Hardware
* Bridges
* Gateways
* Routers
Intranets
* Internal Web for an Organization
* Patterned after the Internet
Uses of Telecommunications
* Telecommuting
* Electronic Mail
* Bulletin Boards
* On-Line Information Services
* Teleconferencing
* Facsimile Transmissions
Impact of Telecommunications
* Global Communication
* Underground Bulletin Boards
* Exchange of Ideas and Facts