The regular JimStim can test the main board on your MS3. But what if you'd like to see the inputs and outputs on the MS3X expansion card in action, too? Now it's easy - just add a JimStimX! Use the three pull-off jumpers on the JimStim to connect the 5 volt power, ground, and cam signal to the JimStimX, and you can test the outputs with the LEDs and use the DIP switch and three trim pots to control the four on/off and three analog inputs. Available in kit form or fully assembled for a few bucks more.