The SPD (Spectra Display) program displays data from the ATNF correlators/spectrometers, either in the lag domain - the correlation function, as measured directly by a correlator - or in the frequency domain - the spectrum which results from the Fourier transform of the correlation function in the case of a correlator, or from direct measurement in the case of a spectrometer. The user can select which of the products contained within the correlator/spectrometer configuration to display and in what form to display them.

SPD can also display time bin profiles and time bin images for correlator/spectrometer configurations which provide time or pulsar binning. In the case of pulsar binning, the de-dispersed pulsar bin profile can be displayed.

Note: For the correlation function, the default action is to display only that part of the function which is actually measured in the correlator. For autocorrelations, this will generally be only be the positive lags. If negative lags are requested for autocorrelations with the 'lags' command, the positive lag measurements are mirrored into the negative lags for display.