What does it mean to transmit digital data over an analog signal?

Transmitting digital data over an analog signal involves converting the digital information into an analog format so that it can be sent over communication channels that are designed for analog signals. This process is facilitated by modulator/demodulator (modem) technology.

When digital data needs to be transmitted, such as data from a computer, it is in a binary form consisting of 0s and 1s. Analog signals, on the other hand, are continuous waves that can vary in amplitude or frequency. The modulator converts the digital signal into an analog signal by varying one or more characteristics of the analog wave (like amplitude, frequency, or phase) with the digital information. At the receiving end, a demodulator converts the analog signal back into a digital format, restoring the original data.

Thus, the essence of transmitting digital data over an analog signal primarily revolves around this conversion process, which is critical for successful communication over mediums traditionally suited for analog signals.