"Analog" and "digital" do not refer to the physical process of transmission, such as radio waves, but the interpretation of the signal. A digital system has rul

"Analog" and "digital" do not refer to the physical process of transmission, such as radio waves, but the interpretation of the signal. A digital system has rules for forming and interpreting the signal, so that the transmitted and received messages are identical. These rules typically involve things like signal level thresholds and timing. Well-engineered systems have "noise immunity" meaning that the thresholds are well above the noise floor, making the likelihood of an error negligible. If you hang an oscilloscope probe on a "digital" signal, such as the data lines on a memory chip, it might look like a frightening mess, but so long as the rules are obeyed, data transfer occurs faithfully. In a true analog medium, there's no way that the receiver can make out precisely what was sent, and two receivers will get different information.