| Back to the Basics: Communication Devices |
Since
today's communication technology can be confusing for many
people, Genesis Global, Inc. wants to go back to the basics
and take a brief look at the various types of communication
channels available. This article addresses eight basic factors
which affect data transmission: "transmission rate—frequency
and bandwidth; line configurations—point-to-point
versus multipoint; serial versus parallel transmission;
direction of transmission—simplex, half-duplex, and
full-duplex; transmission mode—asynchronous verses
synchronous; packet switching; multiplexing; and protocols."
Transmission Rate—Frequency and
Bandwidth
Frequency: Transmission rate (or speed)
of information traveling through a channel can be effected
by wave frequency. For example, twisted-pair telephone wires,
coaxial cables, and fiber-optic cables are channels that
send data at different speeds due to their different wave
frequencies.
Bandwidth: Bandwidth is a channel that
can send several speeds of frequency all at the same time.
The more bandwidth there is, multiple frequencies of data
can be transported at a faster speed. “The rate of
speed of data through the channel is expressed in bits per
second (bps), kilobits per second (Kbps), or megabits per
second (Mbps).”
Line Configurations—Point-to-Point
vs. Multipoint
Point-to-Point: “A point-to-point line directly connects the sending
and receiving devices, such as a terminal with a central
computer.” This method keeps data private and secure
since data is transmitted from one device to another. A
router connected to a PC is a simple example of a point-to-point
connection.
Multipoint: “A multipoint line is
a single line that connects several communications devices
to one computer.” For instance, one line of coaxial
cable can transmit data to three or more routers.
Serial vs. Parallel Transmission
Serial: Bits of data travel through channels
sequentially—one bit of data follows the next (as
in the case of twisted-pair telephone lines). This is equivalent
to cars moving down a one-lane road, one behind the other.
Parallel Transmission: Bits of data “are
transmitted through separate lines simultaneously. The arrangement
resembles cars moving in separate lanes at the same speed
on a multilane freeway.”
Direction of Transmission—Simplex,
Half-Duplex, and Full-Duplex
Simplex: When two computers are in communication,
data can flow through a channel in only one direction. For
example, the traditional television only sends information
out.
Half-Duplex: When two computers are in
communication, data can flow in both directions. CB and
marine radios can send and receive information, but not
at the same time.
Full-Duplex:
When two computers are in communication, data can flow in
both directions at the same time as seen in telephone conversations.
Transmission
Mode—Asynchronous vs. Synchronous
Asynchronous: (also called start-stop transmission)
In this mode, data is sent one byte (or character) at a
time. "Each string of bits making up the byte is bracketed,
or marked off, with special control bits. That is, a "start"
bit represents the beginning of a character, and a "stop" bit represents its end."
Synchronous: (timed transmission)
"Instead of using start and stop bits, synchronous
transmission sends data in blocks. Start and stop bit patterns
called sync bytes, are transmitted at the beginning and
end of the blocks. These start and end bit patterns synchronize
internal clocks in the sending and receiving devices so
that they are in time with each other." Packet Switching Messages
are broken or divided into packets when sent and pieced
back together to form the original message within a network.
This is not suitable for real-time video and voice transmission.
Multiplexing Multiplexing
allows a single communications line to carry multiple signals
at the same time. For example, trunk networks transmit thousands
of telephone calls on a single line at the same time.
Protocols Protocols
are the rules that govern the exchange of information between
software and/or hardware in a communications network.
To conclude, communication technology does not have to be
confusing. As technology continues to evolve through time,
so does our language. By expanding your technical vocabulary,
you will be able to make more informed decisions on network
hardware and network peripherals. Occasionally reviewing
these basic terms, helps us to be more aware of the different
data channels required for communication devices.
_________
About Genesis Global's Author:
Debbie
Jensen, an expert writer for business and technology for Genesis Global, has a Bachelor's Degree in Visual Communication (Multimedia). With her twenty year history of creative expressions and formalized study of Information Technology of digital print/web design and development, she is now publishing articles about networking for Genesis Global.
Resource:
Computers,
Communications, & Information, 2000. McGraw-Hill Companies,
Inc.
Articles Directory
|
|
