Describe Methods By Which Electrical Signals Convey Information?

Any measurable characteristic of an electrical signal can be used to convey information. These would include
- presence or absence
- amplitude (voltage, current)
- phase
- frequency
- spectral characteristics (bandwidth, signal to noise ratio, presence of certain frequency components or certain forms of modulation)
- auto-correlation or correlation with other electrical signals
- pulse width or position or other time-related characteristic.