A block diagram of the TUNA II virtual-instrument software is available as an Adobe .pdf file. The virtual instrument program was written to run under LabVIEW 5.1 and is available as a .zip archive. The virtual instrument requires that both a GPIB card and a PCI-1200 multifunction I/O card are present. The external signal generator (Agilent 33120A) is controlled by the GPIB bus; all other control and data-acquisition functions are handled through the PCI-1200.