Chapter 3

Chapter 3 - 1 2 3 4 Chapter 3 Wired Wireless Communication...

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1. Moving Data: Bandwidth and Modems a. Communications – The process of electronically sending and receiving messages between two points. b. Communication Channels (links) – The path through which messages are passed from one location to the next. i. Analog signals (phones and phone lines) – take data most often audio of the human voice, and translate it into continuous waveforms that travel over comm. Channels. Sent data is limited ii. Digital signals – Convert data into discontinuous pulses in which the presence or absence of electronic pulses represents 1s and 0s. Data arrives in clearer form and transfers much more data than analog at faster rate. 1. DTV systems deliver over 200 stations across digital cable, which not only allows for more stations than analog cable, but more features. c. Messages converted into electrical signals. 2. Bandwidth – The amount of data that can be transmitted through a given comm. Channel. a. Analog expressed in cycles per second, hertz (Hz). b. Digital bandwidth is in bits per second (bps). c. Broadband – Any transmission medium that transports high volumes of data at high speeds greater than 1 Mbps. i. Ideal are 56K for textual data, and 128Kbps+ for web browsing. 3. Modems – comm. Devices used to transmit data over phone lines. a. Modulation is the term for modems sending info to transform computer’s digital signal into analog tones conveyed through phone systems. When receiving, b. Demodulation transforms analog signal back to digital. c. Modems do both and originates from Mo dulation/ Dem odulation d. Two types i. Internal – Fits inside computer system. Powered by PSU ii. External – Separate case and PSU, more expensive. 4. Wired and Wireless Transmission Media a. Wireless media use infrared, radio, or microwave signals. b. Twisted Pair – Two insulated wires twisted around each other, shielding against electromagnetic interference from motors, power lines, and radio signals. i.
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This document was uploaded on 10/09/2008.

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Chapter 3 - 1 2 3 4 Chapter 3 Wired Wireless Communication...

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