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.

　　PTT

　　When the PTT input pin is de?asserted for greater than 80 ms a self test will be performed. If this test is successful the SCR will be fired which will trip the GFCI unit. If the test is unsuccessful the LED［0］ pin will flash indicating a failure.