Mango1, With the T110 II the power supply is auto sensing, so it won't have a switch to change the voltage. The switch was removed due to advancements in technology and to simplify the servers and their setups. Hope this helps answer your question.
I recently purchased a PowserEdge T110 for our church.   However, I see that the power backup unit is setup on a 220v system.   How do I setup the PE T110 11 to accept 220v power?   Previous older tower units that I've worked with had a switch in the back but this one does not seem to have one.
Dell PowerEdge T110 II and 220V power supply