A plug-in module that adds sound input and output capabilities to a computer; it is a type of add-in card. Some systems have the module as part of their original design. The sound card takes digitized audio signals from the processor and converts them into an analogue audio signal used to drive headphones or as input to an audio amplifier or active speakers. The majority of sound cards are PC compatible. The input and output resolution of the D/A converters on these are typically 16, 24, or 32 bit. The input and output sample rates available may vary from 8 kHz through the CD rate of 44.1 kHz up to 192 KHz. Some have built-in amplifiers and mixing capabilities. Most sound cards have some form of digital synthesizer while the higher-end systems use digital signal processing technology and can perform wave-table synthesis from samples of real instruments loaded onto either RAM or ROM. See also multimedia.