Turn on the Midas DL231 using the power switch(s) on the rear panel. For this process, you only need one of the power supplies on. To find the software version on the unit, press and hold in the 'Menu' button. The software will then drop into a numbered Menu. Using the Up or Down arrows, scroll round to option 8 - S/W Version. Press the 'Enter' button and the software version the unit is running will be displayed. Pressing the 'Menu' button twice will drop you back to the normal operating page.