A device for quickly determining the correct phase/polarity of audio component power connectors. The battery-operated test device offers the simplest possible operation since it is only necessary to plug the power connector of the device to be tested into the phase detector. The phase is displayed by 2 LEDs in a single test process. The corresponding phasing at the power socket can be determined with the enclosed circuit tester. The device is so sensitive that even the condition of the mains supply line enters into the measurement result.