ECT 250: Survey of e-commerce technology
Networking
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Fundamentals of Data Communications Systems and Networking, Slides of Fundamentals of E-Commerce
An overview of the basic components of data communications systems, the conversion of digital to analog signals, and the different types of communication links such as wire pairs, coaxial cables, fiber optics, microwave transmission, and satellite transmission. It also covers modem speeds and the use of modems for conversions.
Typology: Slides
2012/2013
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ECT 250: Survey of e-commerce technology
Networking
2
In a network, communications equipment is usedto connect two or more computers allowing thesharing of various hardware, software, and dataresources.The basic components of a data communicationssystems used to transmit information are:• A sending device• A communications link, consisting of both
communications hardware and software.
- A receiving device
Networking
4
If the wires in place for communication use analogsignals, digital data must be converted to an analogsignal in order to be transmitted.•The digital signal is transformed into an analog
wave in a process called
modulation
•The analog wave is transmitted.•The analog signal is converted back into a digital
signal during a process called
demodulation
Piggybacking technology
5
A
modem
is the hardware device that does these
conversions. (Short for
mo
dulate/
dem
odulate).
Modem speeds are referred to by the number ofbits per second (bps) at which they can transmitand receive data.• The earliest modems has speeds around 300 bps.• Later modems had speeds ranging from 9600
to 33,600 bps.
- Today modems have speeds of 56,000 bps (or
56 Kbps).
Modems
7
Sometimes called twisted pair, this media useswire pairs twisted together to form a cable. Thecable is then insulated.Wire pairs are popular since this form of cablingis already installed and available in most places(telephone cabling).It is, however, susceptible to electrical interference,called
noise
Wire pairs
8
A coaxial cable is a single conductor wire that isthickly shielded.• It sends a very powerful signal.• It is used for cable television.• These cables can transmit data at a very fast
rate. Bundles of these cables can be laid undergroundor under the sea.
Coaxial cables
10
In microwave transmission the signals are wirelessand can travel through the atmosphere.Signals can, however, be blocked by the curvatureof the earth. (Line of sight transmission)To prevent this, relay stations are located in highareas and are used to retransmit data to other relaystations.