I need a circuit that will turn on low voltage (5-12VDC) when a contact closure is closed. I already have the working contact closure. One more thing...no voltage can be applied to these contact closures in the needed circuit. Thank you very much.

 

You don't really give enough information, what exactly do you want the circuit to do?. Any electrical switch (or contact) works off electricity, so it's impossible to have 'no voltage applied'. It's easy enough to have 'very little voltage applied' - but again, why do you have this requirement?.

 

Well, if i understand the question, a relay may work for you.