Smart Life Model WD933 : is a ground-fault circuit interrupter (GFCI Receptacle)

The ground-fault circuit interrupter, or GFCI, is a fast-acting circuit breaker designed to shut off electric power in the event of a ground-fault — for use instead of a normal socket to prevent electric leakage especially in the risky areas

An extension cord can be wired to an ordinary socket to have the same protection against electric shock.

Rated current at 16A, leakage protection at 10mA sensitivity, cut off the leakage within 0.03 seconds.