A unique proving unit that comes complete with a CALCHECK feature for use with installation testers and 5 stepped voltage thresholds matched to common two pole tester thresholds. This additional feature makes it easy to verify the insulation and low resistance ranges on many multifunction and single function insulation testers on-site. Features and Benefits: CALCHECK function is Ideal for identifying potential calibration issues with a multi-function tester prior to certifying a new wiring installation or carrying out a condition report Safely proves the operation of voltage indicators and test lamps up to 690V Long battery life and a low battery indicator Typical Applications: Electrical installations and maintenance