Yamaha DTXpress/DTXplorer/DTXtreme

What is the purpose of the DTXpander? Does it allow you to combine  
two single zone peizo pads into one dual zone input like you would on 
input 9/10? I am already using input 9/10 for this purpose and have 
made my own splitter. I have a background in electronics but I'm 
having trouble understanding the DTXpander circuit. I have the 
DTXpress I(one) and I'm wanting to add more pads(triggers). If the 
DTXpander circuit will allow this to happen what inputs can I use? 

Thanks In advance for your replys.........