We have developed a portable, external digital/analogue converter (E-DAC) to get a low cost device with sampling rates up to 600 kHz per channel (16 bit). Two D/A channels are available at the moment, simultaneous data input is scheduled. The attenuation (step size 0.375dB, range 0-90 dB) of the signal takes place after the digital/analogue conversion in order to retain a high signal-to-noise ratio. The D/A-converter operates independently of the main processor to avoid interrupts and timing problems. The standard enhanced parallel port (EPP) is used for data transfer between host and the external device, because it is available at most PCs or notebooks, and the data transfer speed is reasonable. A software program (E-DAC-Control) has been designed to control the output of digitized signals. It will run under Windows 3.x and higher. This computer program allows generation and manipulation of sine waves or sweeps as well as the import/export of modified data files. Additionally, complex programs can be composed, employing different signals, variable repetition rates, pause durations and attenuation levels.
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