Transmission Media: Wired and Wireless

Hello students, welcome to Kwickprep. Your home internet may come on a thin glass thread, and your earphones need no wire at all. How can data travel through glass and air? Today we will learn wired and wireless transmission media, and how to choose the right one.

First, the meaning. A transmission medium is the path that carries data from the sender to the receiver. In wired media, also called guided media, the data travels along a cable, so the cable guides it. In wireless media, also called unguided media, the data travels through air or space as waves, with nothing to guide it.

Let us begin with the most common cable, twisted pair. It has pairs of copper wires, twisted around each other. The twisting cuts down noise, which means unwanted disturbance from other wires. It is cheap, light and easy to fit. It connects computers in school and office networks, and also landline phones. Its signal becomes weak after about one hundred metres, so it suits short distances.

Next is coaxial cable, often called coax. It has one copper wire in the centre, wrapped in plastic insulation. Around that is a metal mesh shield, and then an outer plastic jacket. The shield blocks noise, so coax carries signals better than twisted pair. You have seen it as the cable television wire that goes into a set top box.

The fastest cable is fibre optic. It carries data as pulses of light through very thin threads of glass or plastic. It is very fast and carries data over very long distances, even under the sea. Light is not affected by electrical noise, and the cable is hard to tap secretly. But it is costly, and joining two fibres needs special skill and tools. Internet backbones between cities and fibre broadband at homes use it.

Here is a quick comparison. Twisted pair and coax carry electric signals, while fibre carries light. Copper cables give low to medium speed, and fibre gives very high speed. Copper picks up some electrical noise, but fibre picks up none. Copper is cheap, and fibre is costly. Copper suits short distances, and fibre suits very long ones.

Now let us move to wireless media, starting with radio waves. Radio waves spread in all directions from the antenna. They can pass through walls and travel long distances. F M radio, mobile phones and Wi-Fi all use radio waves. Because anyone nearby can pick them up, the data must be protected with passwords and encryption, which means scrambling it into a secret code.

Microwaves are the next type. They travel in a straight line, so the sender and receiver must see each other, and we call this line of sight. That is why you see dish antennas on tall towers, facing each other across long distances. Communication satellites also use microwaves to connect far away places, like television signals sent to your dish. Heavy rain and tall buildings can weaken or block them.

The third wireless type is infrared. It works only over a very short range of a few metres. It needs line of sight and cannot pass through walls. Your television and air conditioner remotes use infrared, which is why you must point them at the device. Since it cannot leave the room, nobody outside can catch the signal.

Let us compare the three waves. Radio waves travel far in every direction and pass through walls, as in mobile phones. Microwaves travel far but only in a straight line, as between towers and satellites. Infrared covers just a few metres in line of sight, as in a remote control.

Two wireless technologies you use every day are built on radio waves. The first is Bluetooth. It is a short range radio link, usually about ten metres. It connects personal devices, like earbuds, a smartwatch or a wireless keyboard, to your phone or laptop. It uses very little power, so small batteries last a long time.

The second is Wi-Fi. Wi-Fi builds a wireless local area network, which means a network inside a home, school or office, using radio waves. A router, or an access point, creates the network, and devices join it. Indoors it usually reaches a few tens of metres. Wi-Fi is much faster than Bluetooth, and you should always protect it with a strong password.

Here is Bluetooth against Wi-Fi. Bluetooth reaches about ten metres, while Wi-Fi reaches a few tens of metres. Bluetooth is slower, and Wi-Fi is faster. Bluetooth uses very little power, and Wi-Fi uses more. Bluetooth is best for earbuds and watches, while Wi-Fi is best for internet on phones and laptops.

Now let us choose a medium for a situation, which is a common exam question. For a school computer lab, twisted pair is best, because it is cheap and the distances are short. To link two cities at high speed, choose fibre optic. For a remote hilly village where laying cables is hard, a satellite link using microwaves works. For earbuds, Bluetooth is right because the range is tiny and power use is low. To change a television channel, infrared is enough, because it only needs to work in one room.

Pause the video and choose the medium yourself. A hospital needs a fast link between two buildings, two kilometres apart. The cable passes near big machines that create electrical noise. The answer is fibre optic, because it covers the distance at high speed, and light is not disturbed by electrical noise.

Let us revise what we learned today. Wired media are twisted pair, coaxial and fibre optic cables. Fibre is the fastest and free from electrical noise, but it costs the most. Radio waves spread in all directions, while microwaves and infrared need line of sight. Bluetooth is short range and low power, and Wi-Fi covers more area at higher speed. Always choose a medium by distance, speed, cost and noise.