The T&R KV30-40 High Voltage AC Test System as an output voltage from zero to the maximum rated output voltage. A zero-voltage interlock is provided, ensuring that the output may only be energised with the voltage control at zero. The unit features automatic mains voltage selection and an external 24Vdc interlock circuit for connection of emergency off switches and interlock switches on the test enclosure. The output voltage and current are metered by large, linear analogue instruments. The unit have a x0.5 range on the voltmeter and a x0.1 range on the mA meter. The test object and output are protected by an adjustable electronic current trip. The trip level may be set to 10-110% of the rated output in 10% steps. Breakdown of the test object is visibly indicated and the unit must be manually reset after a trip condition before testing can be resumed.