Bandwidth: Example

Do you remember modems?
This device converts analog signals into digital signals and vice-versa.

Early modems transmitted at 300 or 1,200 bps. Later speeds of 2,400 or 4,800 and 9,600 bps were available. Today you can buy modems that can transmit at 14,400 or 28,800 bps.

What does that mean?

Let's use the units that we invented earlier: 1 novel = 4 Mbits
How much time will it take to transfer a novel?

MODEM TRANSMISSION SPEED
TIME

300 bps
3 h 42 min 13 s

1,200 bps
55 min 33 s

4,800 bps
13 min 53 s

14,400 bps
4 min 38 s

28,800 bps
2 min 19 s

The higher the bit rate, the faster the transmission.

But how do we go from some information like a human voice or a picture to a string of 1's and 0's?

MODEM TRANSMISSION SPEED	TIME
300 bps	3 h 42 min 13 s
1,200 bps	55 min 33 s
4,800 bps	13 min 53 s
14,400 bps	4 min 38 s
28,800 bps	2 min 19 s