In remote control switching circuits in certain applications, what provides the low voltage?

• A. Batteries
• B. Power supplies
• C. Step-down transformers
• D. AC mains

Answer: (C)

A step-down transformer supplies the low voltage by taking the higher mains voltage on its primary and delivering a lower-voltage AC on the secondary, with galvanic isolation between the two sides. In remote control switching circuits, this isolated, lower-voltage source is used to power relays or control electronics, and it can be rectified to DC if needed. While batteries or dedicated power supplies can provide low voltage, the standard method described in these applications is to derive it from the mains using a step-down transformer, which is specifically designed to reduce voltage safely. The AC mains is the high-voltage source, not the low-voltage supply.