The Bender AGH420 is a coupling device designed for the insulation monitoring of unearthed IT systems (AC, DC, or AC/DC) that contain galvanically connected rectifiers, inverters, or DC converters. It is used in conjunction with Bender ISOMETER® devices of the iso685 or iso1685 series. The AGH420 ensures the reliable coupling of the measuring pulses from the ISOMETER® onto the live conductors of the system, enabling accurate insulation fault detection even in complex power supply systems with high leakage capacitances.