I was watching the Screen Savers yesterday (a computer tv show) and it was talking about how modems work. It said that the computer sends a low tone for a 0 and a high tone for a 1. I was thinking phone lines can carry more than two different tones, so maybe connections would be alot faster if the data was sent as hexidecimal instead of binary and you used 16 different tones instead of 2. See what I am saying? It makes sense to me

I think they do already.

True, but you also need to take noise into consideration. Unfortunately, the physical world is imperfect. =) Noise creeps in and alters signals, voltage levels. By limiting the different kinds of signals we send, we achieve noise immunity.

Think of it like this. Let's say you can transmit a maximum of 5 volts over a line that has a max of 0.1V noise. If you decided to make that 100 levels of information, you'd be able to send quite a lot of data at once. But is 4.5V really 4.5V, or 4.4V with 0.1V noise, or 4.55V with 0.05V noise?

By drastically cutting down on the number of levels, we can use less sensitive modems on either end and we don't have to worry so much about noise. Of course, you still need your error-correcting and synchronizing algorithms, but that's another discussion. =)

About error checking and stuff... I've noticed communication with serial cable isn't very stable, you often lose a few bytes of data here and a few bytes there.

Serial's not as bad as parallel. =) You get lots of crosstalk when the lines get too long, which is why parallel cables are usually pretty short.

I've never communicated with paralell cables, I don't have any

why do you guys use parallel cables etc anyways ?
[addsig]

hehe, you should know, robert want to use his ooold oold computers (well, not THAT old but like 386es) for surgfing and he doesn't wanna get NICs even though there is a small chance he can get some. So parallel it is .