The NCS37010 is a fully UL943 compliant signal processor for GFCI applications with self test and lockout. The device integrates a flexible power supply (including both shunt and LDO regulators), differential fault, and grounded-neutral detection circuits. Proprietary impedance measurement and signal processing techniques are used to minimize the number of external components and improve performance. The device also includes a specialized DSP controller that offers best in class immunity to nuisance loads without the need for external analog filters. At power up the NCS37010 performs a self test at 60ms and removes the lockout if the test passes. This self test consists of a differential, ground-neutral and solenoid test.