Electrical signals can be used for two purposes.
- Representation and transmission of information
Current can be turned on and off to represent digital information or continously modulated (Bell’s phrase was an “undulatory current”) to represent analog information. Currents imply wireline communications and circuits. The electric field can be modualted in similar ways, yielding wireless communication and processing.
- The transmission of power
Electrical signals—currents and fields—also carry power.
Electrical engineering is based on the flow of current and the electromagnetic field, properties of the electron. Although the word electron was only applied to the electric charge in the late nineteenth century, the history of electrical science and engineering goes back much farther. Electrical engineering also hinges on the mathematics of the signal. Without signal theory, the physical properties of the electron and the electric field cannot be exploited.