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Unit 6: Information and Communications Technology
The cost of the transmission medium is also one of the important criteria while selecting Notes
the media.
The speed of transmission varies from one medium to another.
Now, let us discuss the characteristics of each transmission medium along with their uses.
6.5.1 Two Wire Open Lines
The simplest of all transmission media is the two wire open lines. This medium consists of a pair
or several pairs of metallic wires made up of copper or aluminium, which are insulated from each
other When the medium has only one pair, it is called a simple wire pair as shown in figure 6.1 and
when it has several pairs, it can be in two forms- Flat Ribbon connector and Multicore cable. In Flat
Ribbon connector, each pair of wires run parallel and are moulded into the form of a flat ribbon
case as shown in figure 6.2. However, in Multicore Cable, all wires are enclosed in a single
protected cable shown in figure 6.3.
Figure 6.1: Simple wire pair
Matallic Wire Insulation Material
Figure 6.2: Flat ribbon connector Figure 6.3: Multicore cable
Uses of Two Wire Open Lines. Two wire open lines medium is used for transmitting data to a
short distance. This type of media can transmit data up to 50 meters with speed less than 19200 bps
(bits per second).
6.5.2 Twisted-pair Cable
This is the oldest and most common medium for connecting computers and other devices. Twisted-
pair cable consists of a pair of insulated copper wires (1 mm thick), which are twisted together in
helical form as shown in Figure 6.4. The telephone wire is an example of a Twisted-pair cable.
Figure 6.4: Twisted pair cable
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