I am looking for a simple way to detect 120 or 240 VAC on a power strip. If voltage is 120, I want to direct voltage to a transformer for step-up to 240 VAC then apply voltage to a device. If voltage is 240 VAC, I want to bypass transformer & apply directly to device. In other words, device will always see 240 VAC regardless of source voltage. Load is 4 amps or less.