A cardiac signal generator includes a first circuit, a user input device, an output display, and a processing circuit. The first circuit provides, according to any of predetermined plurality of settings, cardiac signals comprising a repeating cardiac waveform, and respiratory signals comprising a repeated respiratory waveform. The output display includes a plurality of indicators, each indicator corresponding to one of the plurality of settings. Each setting includes a combination of a frequency of repetition of the cardiac waveform and a frequency of repetition of the respiratory waveform. The processing circuit causes the first circuit to provide cardiac and respiratory signals according to a selected one of the plurality of settings. The processing circuit is further configured to receive a signal from the user input device, and change the selected setting from a first setting of the plurality of settings to a second setting of the plurality of settings responsive thereto.