Trumpy, AFCI stands for Arc Fault Circuit Interrupter. It "looks" for the characteristics of an arc between hot and neutral. They are required for bedrooms under the latest NEC. An AFCI also provides GFCI protection, but not Class A protection. Class A requires the device to trip at about 5mA of ground current and AFCI's trip at well above 5mA. The SquareD AFCI breaks at 50mA. Still sensitive enough for a solenoid tester to trip it.
