Digital signals are converted into analogue signals primarily for signal transmission. This process allows digital data, which consists of discrete values, to be transmitted over analogue mediums, such as telephone lines or radio waves, which require continuous signals. The conversion enables compatibility with various communication technologies and ensures effective transmission over distances where digital signals might not be easily propagated.

Additionally, analogue signals can be modulated (varying frequency, amplitude, or phase) to carry more information over the same channel, making it efficient for transmission over various media.