A
transmission media can be defined as anything that carries data from one place
to another. Transmission media broadly divided into two: guided media and unguided media.
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| Transmission Media |
Guided Media
Guided media are those that
provide a channel from one device to another. Here we consider three guided Medias,
twisted pair cable, coaxial cable and fiber optic cable.
Twisted Pair Cable
A twisted pair cable consists of two insulated copper
wires. Typically, the thickness of each wire is 1 mm. One of the wires is used
to carry signals to the receiver, and the other is used only as a ground
reference.
The receiver uses the difference between the two. The wires are
twisted together in a helical form. The twisting of wires reduce the electrical
interference. Twisted pairs can be used for transmitting either analog or
digital information. The bandwidth depends on the thickness of the wire and the
distance traveled, but several megabits/sec can be achieved for a few
kilometers in many cases.
Twisted pair cable is available in two forms:
unshielded twisted pair (UTP) cable and Shielded Twisted Pair (STP) cable.
Shielded twisted pair cable has a metal foil or braided mesh covering that
encases each pair of insulated wires.
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| Twisted Pair Cable |
Electrical Industries Association (EIA) has developed
standards to grade UTP cables by quality.
Category 1
Basic twisted pair cable using in telephone systems.
Data rate is less than 0.1Mbps.
Category 2
Used in T-1 lines support data rate up to 2 Mbps.
Category 3
This category of UTP cable used for data transmission
of up to 10 Mbps.
Category 4
Support transmission rate up to 20 Mbps
Category 5
Support transmission rate up to 100 Mbps.
Category 6
Support data rate up to 200 Mbps.
Category 7
Support data rate up to 600 Mbps.
The most
common UTP connector is RJ45 (Registered Jack 45).
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| RJ 45 |
Next : Coaxial Cable
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