The analyzer program works in conjunction with the sound card on your computer. Most computers have a sound card built into the system; however, an external USB based sound card is often a better choice due to more robust connectors and improved performance. Plug the audio signal to be measured into the Line-In or Microphone jack on the sound card. SpectraPLUS-RT then uses the card to perform an "Analog-to-Digital" conversion on the audio signal. This digitized audio is then passed through a math algorithm known as a Fast Fourier Transform (FFT) which converts the signal from the time domain to the frequency domain. The CPU on your computer is used to perform this transformation.
The analyzer and continuously processes the input signal and plots the spectral data.
See also: Setting up the Analyzer