24vdc

How would you step down the voltage to power the radio , I was thinking using a potentiometer or what? Im a spark chaser not whiz at this stuff.

I purchased a Pyramid 7000 Master Clock to play timed school bells. I have to purchase the bells. The original system plays 24VDC bells, but they built a DC to 10 Amp AC relay that I bought additionally so it can play both 24VDC and AC bells. (link to relay...