A transmission medium in communication is the path traveled by the communication signal from the transmitter to receiver.
Transmission of communication signals are done through different mediums. Communication signals could be carried through copper wires, as well as through satellite channels.
When travelling signal waves are superposed on each other, they are called a linear medium.
Transmission media can be classified broadly as:
The guided and the unguided are the major transmission media in communication networks. Below, we explain both media with examples.
A guided transmission medium is also known as bounded transmission. This means that signal transmission is done through a narrow path with the use of physical links.
Some examples of the guided means of communication are given below:
A twisted pair cable is mostly used in the transmission of telephone signals and signals in Ethernet networks. A twisted pair cable is comprised of two distinct insulated copper wires which are twisted together.
Coaxial cable is mostly used in the transfer of radio frequency in transverse electromagnetic waves. It is made up of copper cable and can be used in the transfer of high-frequency signals at low loss. Its an example of a guided means of signal transmission.
Fiber optics are made of glass or plastic and are comprised of small diameters bundled together to make a fiber-optic cable, they transmit signals as light pulses and can travel over long distances. It applies well for communication signal transmission.
An unguided transmission is where electromagnetic waves travel in an unguided form. They could travel through air, vacuum or seawater. In unguided transmission there is no involvement of a physical medium for the transmission of the signal. Some examples of unguided transmission are given below:
Microwave signals are electromagnetic waves with frequencies ranging from 1Ghz to 300Ghz. Microwave signals are clearly unguided and unidirectional in nature, meaning the sender and receiver end of the signal has to be aligned for signal propagation to be complete.
Radio wave signals are electromagnetic waves with frequencies ranging from 3KHZ and 1GHz, they are omnidirectional in nature, meaning the receiver and transmitter end of the signal has no need of alignment for a perfect signal transmission. We apply this transmission in our AM and FM radio stations, where signals can be received at any location within frequency range without the need to align the devices.
Infrared signal transmission has been in use for such a long time that it is seen in the operation of TV remotes as well as other device connections at a close range. It uses the light spectrum to send a focused light beam to a receiver. In infrared transmission, a focused lens is used by the device transmitting the signal while a collective lens is used by the device receiving the signal. It is a kind of unguided means of transmission with very short distance of operation.
Guided and and unguided transmission media are both important because they help guide communication signals to their respective ends.
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