We seek to reliably exchange, in the least amount of time possible, information over some channel. Why use digital communications?
Exchange of information requires propagation of some flux through some medium (for this reason, information cannot be transmitted faster than the speed of light in a vacuum). Variations in the measured flux indicate various states. Some examples include:
- Sound (variations in air pressure)
- Light intensity in optical media
- Voltage intensity along a wire
Systematic transformations of the flux along the channel do not represent a loss of information, provided they're known and can be corrected for. Every channel, however, will introduce some random distortion to a signal.