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ELECTRONIC COMMUNICATIONS
A SYSTEMS APPROACH
CHAPTER
11
Computer
Communication and
the Internet
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Alphanumeric Codes
• The ASCII Code
 American Standard Code for
Information Interchange (ASCII)
• 7-bit code used for representing
alphanumeric symbols with a distinctive
code word.
 Developed for purpose of coding binary
data.
 ASCII-7
• Adopted international standard.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Alphanumeric Codes
• The EBCDIC Code
 Extended Binary-Coded Decimal
Interchange Code (EBCDIC)
• 8-bit alphanumeric code.
• The Baudot Code
 Alphanumeric code based on five binary
values.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Alphanumeric Codes
• The Gray Code
 Numeric code representing decimal
values 0 to 9.
 Based on relationship that only one bit
in a binary word changes for each
binary step.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Computer Communication
• Asynchronous system
 Transmit and receive clocks free-run at
approximately same speed.
• Synchronous system
 Both sender and receiver exactly
synchronized to same clock frequency.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Computer Communication
• Universal Serial Bus (USB) Port
 Universal high-speed serial
communications interface.
• See Table 11-2: The USB Wire Colors and
Functions
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Table 11-2
The USB Wire Colors and Functions
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Computer Communication
• IEEE 1394
 High-speed serial connection for
computers and peripherals; developed
by Apple (FireWire).
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Computer Communication
• RS-232 Standard
 Older serial data communications
follows standard (RS-232 C).
 Means of interfacing computer with
modem.
 Defined signal levels and different lines
used.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Computer Communication
• RS-232 Line Descriptions




Ground pins
Data signal pins
Handshaking pins
Equipment ready pins
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Computer Communication
• RS-232 Line Descriptions
 Signal detect pin
 Ring indicator pin
 Other pins
• See Table 11-3: Overview of Current
Serial Computer Communication
Standards
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Table 11-3 Overview of Current Serial Computer
Communication Standards
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Computer Communication
• RS-422, RS-485
 Uses differential technique that provides
significant improvement in performance
and greater distances and capacity to
support higher data rates.
 Supports multidrop applications.
• See Table 11-4: Standard Computer Bus
Interfaces
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Table 11-4
Standard Computer Bus Interfaces
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Table 11-4 (continued)
Interfaces
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Standard Computer Bus
Copyright © 2014 by Pearson Education, Inc.
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Local-Area Networks
• Local-Area Network (LAN)
 Local computer
• Personal microcomputer-type system.
 LANs defined in terms of topology
(architecture) used to interconnect
networking equipment and protocol for
accessing network.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Local-Area Networks
• Local-Area Network (LAN)
 Carrier sense multiple access with
collision detection (CSMA/CD)
• Bus and star topologies; token passing;
token-ring topology.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Local-Area Networks
• Ethernet LAN
 Baseband CSMA/CD protocol local area
network system.
 Capability for detecting data collisions
(collision detection).
 Ethernet protocol provides information
regarding source and destination
addresses.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Assembling a LAN
• The Office LAN Example
 If network hardware and software
properly set up, all computers will be
able to access server, printer, other
computers.
• See Table 11-5: Common Numerics for
LAN Cabling
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Table 11-5
Common Numerics for LAN Cabling
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Assembling a LAN
• Assembling a Building LAN
 Network where multiple LANs within a
building are connected together.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
LAN Interconnection
• Metropolitan area networks (MANs)
 Two or more LANs linked together
within limited geographical area.
• Wide-area network (WAN)
 Two or more LANs linked together over
wide geographical area.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
LAN Interconnection
• Open systems interconnection (OSI)
reference model
 Developed by International Organization
for Standardization (ISO).
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
LAN Interconnection
• Interconnecting LANs
 Switch
 Routers
 Gateways
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Internet
• Internet Protocol (IP) Addressing
 Unique address that tells on which
network the computer is located.
 Assigned by Internet Assigned Numbers
Authority (IANA).
• See Table 11-6: The Three Classes of IP
Networks
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Table 11-6
The Three Classes of IP Networks
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
IP Telephony
• IP telephony (voice-over IP)
 Telephone system for computer
networks.
 Technologies comparable to private
branch exchange (PBX) telephone
systems while maintaining flexibility of
computer networks.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Interfacing the Networks
• Modem Technologies
 To transmit data via a phone requires
conversion of a signal within 300- to
3400-Hz range; conversion provided by
a modem.
• Cable Modems
 High-bandwidth network to deliver highspeed, two-way data.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Interfacing the Networks
• Integrated Services Digital Network
 Data communications link for both voice
and data using a set of standardized
interfaces.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Interfacing the Networks
• xDSL Modems
 High-speed internet access technology.
 DSL
• Digital subscriber line.
 Uses copper telephone lines for carrying
data.
• See Table 11-7: xDSL Services and Their
Projected Data Rates
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Table 11-7
Rates
xDSL Services and Their Projected Data
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Troubleshooting
• Common maintenance situation for
larger LAN installations is to set up a
help desk.
 OSI model to troubleshoot.
• Problems with unshielded twisted-pair
wiring
 Pairs become crossed or split up; wrong
kind of connector used.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved
Troubleshooting
• Keep good-quality wiring diagrams of
network installation.
Electronic Communications: A Systems Approach
Beasley | Hymer | Miller
Copyright © 2014 by Pearson Education, Inc.
All Rights Reserved