D/A

Digital to analog conversion is what lets us play back the growing masses of digital information. A CD is a gleaming plastic disk, but not worth the $14.95 price until those bits have been turned back to music by playing them through a chip at 44 thousand per second or so. It also lets digital information move along imperfect communications lines. Modems are modulator/demodulator devices, D/A on the one end and A/D on the other and switching as the need arises. This kind of modulation has to be perfect, or it might as well not have happened at all.