This page is not complete but is a place for me to put together links to useful sites so that you can easily find resources on the web.
Mobile telephones page on mobile phone technology with links to other web resources on mobiles.
Pulse Width Modulation (PWM) is a digital form of modulation used in lamp dimmers and motor speed control as well as the technique used in 1 bit DACs in CD players
There are some other links to interactive pages that will be useful in looking at digital modulation techniques:
Nyquist theory java
Pulse Position Modulation
Shift registers practical
Looking at serial data from a keyboard and mouse questions on serial data transmission