What is a Transmission Medium?
🎬 Watch the 5:55 video of this chapter ↓In The Five Components you met the communication media: the path a message travels along. This chapter is about those paths — the cables and the waves that actually carry every message you send.
1What a transmission medium is
You use transmission media all the time without the name. When you switch on a fan, the electric wire is the medium that carries current from the switch to the fan. When two people talk, the medium is the air.
2Two kinds: wired and wireless
There are two kinds, and the next lesson sorts all six media into them. In wired media a cable carries the signal from node to node, so it can only go where the cable goes — which is why they are also called guided media. In wireless media the data travels through the air as electromagnetic waves, with nothing to lead it: unguided media.
Twisted pair and co-axial cable carry electric signals through copper. Fibre-optic cable carries light through glass. Here are all six, joining the same two buildings.
Pick a medium and watch how the signal gets from Block A to Block B. Drag sideways to turn.
Not to scale. In the infrared view the two blocks are much too far apart for infrared, which is the point.
Each medium has its strengths. The lessons that follow take them one at a time, and the two compared pages show how to choose between them in a case study.
3Check yourself
Which of these is a guided (wired) transmission medium?
What does a fibre-optic cable carry, unlike twisted pair and co-axial cable?
Transmission Media, in 5:55
One animated video of the whole chapter, narrated. Watch it before the lessons for the big picture, or after them to revise.