A/D converter - technical definition

(Analog/Digital converter) A device that converts continuously varying analog signals from instruments and sensors that monitor conditions, such as sound, movement and temperature into binary code for the computer. The A/D converter may be contained on a single chip or can be one circuit within a chip. See codec.

A/D Converters Are Everywhere
Every digital desk phone and cellphone has an A/D converter that turns electronic sound waves into digital PCM code. Every digital camera, camcorder or scanner uses A/D converters to transform the variable charges in CCD and CMOS chips into the binary data that represent pixels. See modem, DSP, CCD, PCM and codec. Contrast with D/A converter.