Bought for slowly waking up vintage valve radios after restoration. Have connected a dual pole switched 3 pin plug socket to the output winding.The transformer works as required but the markings on the dial are between 15V and 20V out depending where the variac is set. Worth checking the output with a digital multimeter before connecting anything where excess voltage may be critical. Normally valve radios will start to play at around 80volts and get louder as the voltage is increased. Once the set has tested for a few hours and proven to be safe I'll remove the variac and run directly on the mains.