h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

A standard phone line can transmit pure binary as a square wave but square waves degarde rapidly. (This is due to the capacitance and resistance of the twisted copper wires, but thats not important right now )
What phones transmit best is a continuously varying (analogue) wave at about 300 cycles per second. What the modem does is put the digital information on top of this efficient carrier wave and take it off again at the other end.
Data can be modulated by altering the amplitude, frequency or phase. The first two are not very good at dealing with the poor transmission integrity of the public switched telephone network so modern modems use phase modulation.

Probably no need to get ultra-techy on most researchers & guide browsers

As long as they can surf the web they're just thankful it all works.

Well if you had sat through Dr. Csenski's ghastly computer hardware lectures you would know that I _have_ to pass on those hard won nuggets of information whenever possible even if it does make me a nerd

I at through a few C.S. lectures myself....

Then Edinburgh University threw me out for hacking. Surely that demonstrated a good understanding of Computer Science and it's mis-applications.

The charming system manager at the University said "If it was up to me you'd never work in Computing!". Perhaps I should try to get in touch and let him know that I now earn rather a lot of money as a systems analyst & programmer!