CIS 267 Business Information Lecture Chapter 2

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CIS 267 Business InformationLecture Chapter 2

• Vaughn L. Lucas

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Information Services

• For the analysis design of information
  networks, information can be categorized as
  requiring one of the following services
• Voice (Audio)
• Image
• Video
• Data

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VIViD Communication

• Voice (Audio)
• telephone, telemarketing, voice mail, radio
• Image
• fax, CAD, publishing, medical imaging
• Video
• television, teleconferencing, multimedia
• Data
• text, numerical information

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Information Sources

• Produce information in two forms
• Digital
• Digital information discrete electrical signal
  or voltage
• Analog
• Analog information continuous electrical signal
  or range of voltages

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Digital Data

• Represented as a sequence of discrete symbols
  from a finite alphabet
• Rate and capacity of a digital channel measured
  in bits per second (bps)
• Digital data is binary uses 1s and 0s to
  represent everything
• Binary digits can be represented as voltage pulses

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Basic Digital Terms

• Bit digit in a binary number
• 1 is a 1-bit number (1 in base 10)
• 10 is a 2-bit number (2 in base 10)
• 10011001 is an 8-bit number (153 in base 10)
• Byte eight bits

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Basic Digital Terms

• Bit digit in a binary number
• Byte eight bits
• Bits Outcomes Use 1 2 basic
  unit of information
• 4 16 hexadecimal digit
• 7 128 IRA character w/o parity bit
• 8 256 byte character w/ parity bit
• 10 1024 bytes in a
  kilobyte of storage
• 13 8192 bits in a kilobyte of storage
• 20 1,048,576 bytes in a
  megabyte of storage
• 23 8,388,608 bits in a
  megabyte of storage

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Basic Digital Terms

• Bytes are usually used in representing quantities
  of storage
• Kilobyte 210 1,024 bytes
• Megabyte 220 1,048,576 bytes
• Gigabyte 230 1,073,741,824 bytes
• Bits are traditionally used in communications

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Basic Digital Terms

• Bits are traditionally used in communications
• Kilobit 1,000 bits
• Megabit 1,000,000 bits
• Gigabit 1,000,000,000 bits
• Bytes are used in discussing computer storage

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Digital Signaling

• represented by square waves or pulses

1 cycle
amplitude (volts)
time
(sec)
frequency (hertz)
cycles per second
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Analog Data

• Continuous signal
• Expressed as an oscillation (sine wave format) of
  frequency
• Example Analog electrical signal generated by a
  microphone in response to continuous changes in
  air pressure that make up sounds

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Basic Analog Terms

• Wave frequency
• Number of cycles occurs in given time period
• Dictates pitch
• measured in Hertz (Hz) - cycles per second
• Wave amplitude
• Height of a wave cycle
• Dictates volume
• measured as a voltage

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Analog Signaling

• represented by sine waves

phase difference
1 cycle
amplitude (volts)
time
(sec)
frequency (hertz)
cycles per second
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Analog Communication

• Information rate and channel capacity measured as
  bandwidth
• Bandwidth - difference between the highest and
  lowest frequencies that are capable of being
  transmitted
• e.g. telephone 3300 - 300 3000 Hz

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Understanding Audio (Voice)

• What makes sound? Vibration of air
• How can we record that vibration?
• How can we convert that to an electrical signal?

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Audio (Voice) Service

• Primary application
• Telephone
• Other applications
• Telemarketing
• Voice Mail
• Audio Teleconferencing
• Entertainment Radio

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Analog Voice Communication

• Primarily used for human voice (telephony)
• Microphone captures voice vibrations, converts
  them to waves than can be expressed through
  variations of voltage
• Examples
• Telephone (3000Hz)
• Hi-Fi Sound (15,000Hz)
• CD (20,000Hz for each of 2 channels)

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Digital Audio

• For good representation, must sample amplitude at
  a rate of at least twice the maximum frequency
• Measured in samples per second, or smp/sec
• Telephone quality 8000smp/sec, each using 8 bits
• 8 bits 8000 smp/sec 64kbps to transmit
• CD quality 44000 smp/sec, each using 16 bits
• 16 bits 44000 smp/sec 1.41 Mbps to transmit
  clearly

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Business Telephones

• Networking implications
• Private Branch Exchange (PBX)
• Three or four digit number to call on premises
• One digit (usually 8 or 9) for an outside line
• Centrex

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Business Telephones
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Data Service

• Common examples of data
• Text
• Numerical information
• Symbols represented by groups for transmission
• 8 bits (octets or bytes)
• See also Table 2.2 on p. 24

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Data Communication

• In this context, we mean data stored on computers
• Already digital, so no conversion necessary
• Bandwidth usually affects speed, but not quality
• Examples?

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Example - Page of Text

• 8.5 x 11 sheet with 1 inch margins
• 3 lines per inch - 27 lines per page
• 10 characters/inch 65 characters/line
• 8 bits per character
• 8 x 27 x 65 14,040 bits overkill
• estimate 10,000 bits per page
• at 56,000 bps, 0.18 seconds per page

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Understanding Images

• To digitize and image, you must break it into
  small units
• More units means more detail
• Displayed units generally called pixels
• Photocell reads each unit, assigns value

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Image Service

• Supports
• Pictures
• Charts
• Drawings
• Image based applications
• Facsimile
• Computer-aided design (CAD)
• Publishing
• Medical imaging

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Image Quality Issues

• More pixels better quality larger size
• More compression reduced quality increased
  speed
• Lossy gives from 101 to 201 compression
• Lossless gives less than 51
• Format (vector vs bitmapped/raster) affects size
  and therefore bandwidth requirements
• Choices in imaging technology, conversion, and
  communication all affect end-user satisfaction

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Video Service

• Applications include
• Instructional television
• Entertainment television
• Teleconferencing
• Closed-circuit TV
• Multimedia

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Video Communication

• Sequences of images over time
• Same concept as image, but with the dimension of
  time added
• Significantly higher bandwidth required in order
  to send images (frames) quick enough
• Similarity of adjacent frames allows for high
  compression rates

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Response Time

• User response time
• System response time
• Network transfer time

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Bandwidth Requirements

• Review chart on page 35 - Figure 2.7
• What happens when bandwidth is insufficient?
• How long does it take to become impatient?
• Is data communication ever fast enough?