Abstract: A technique of controlling operation of a user-adjustable cardiac pacemaker, or a software model thereof, in a training mode is described. A method implementation of the technique comprises generating at least one cardiac event by a feedback-based heart simulator, wherein the cardiac event includes a pulse parameter set defining at least a pulse amplitude. The method further comprises transmitting the at least one cardiac event, or a first signal representation derived therefrom, to an electro cardiogram, ECG, generator configured to generate ECG graphics triggering a user to perform, in the training mode, one or more user adjustments at the cardiac pacemaker or its software model. Further still, the method comprises transmitting the at least one cardiac event, or a second signal representation derived therefrom, to the cardiac pacemaker or its software model, and acquiring stimulus information on one or more stimuli generated by the cardiac pacemaker or its software model.