The default setting for photoelectric simulation is "automatic mode": You can change photoenergy/lightintensity ...etc when the simulation is paused. After you click play button, The simulation will perform the whole experiment automatically. And most of the buttons are disabled until the experiment is done. (only reset is available) If you uncheck "automatic" box. The play/pause button become enabled and paramaters can be changed when the simulation is in paused mode. The simulation will allow you to change parameters after on data point is collected (about 10 s) or after pause button was clicked. Those are setting from the original simulation program. You can change the setting form the GUI interface in EJS. (Right click mouse to open Peoperty windows for those buttons or sliderbars)