Ground Faulc Circuit Interruptors.
- Can be wall outlets. $9.
- Can be plug-in receptacles - [1]
- Arc Fault Circuit Interruptors (AFCI) are another thing - [2]
- Note that GFCI outlets sense differential current, and they are not grounded - [3]
- Portable GFCI - GFCI on a power cord - [4]