Local loop - Analog vs Digital
The information content of an analog signal is conveyed by continuously varying some characteristic such as amplitude, frequency or phase of a voltage or other characteristic of the signal.
Computers, motors, lights and other electrical devices generate electrical noise (unwanted electrical signals), which produce undesirable variations on the information content of an analog signal, thus making it error prone.
Both voice and data (from modems - sent as sounds) are commonly transmitted as analog information.