A debt collectior has initiated proceedings on a debt that is past the statute of limitations. Please help!?

I know that technically, they can't sue me for a debt that is past the statute of limitations, but I have also heard that if I acknolwedge the debt, then it can become "active" again. I can't afford a lawyer. What do I do? Can anyone help me draft a letter that will let them know the debt is past the statute of limitations, but doesn't acknowledge the debt? I called my county clerk and he advised that I try to settle it before it gets to court. I live in Bloomington, Monroe County, Indiana. Please help!