Originally Posted By: DWallach
Wow. I've deployed a bunch of Leviton USB outlets (http://www.amazon.com/Leviton-T5632-W-Charger-Resistant-Receptacle/dp/B00J3PMU4C/) because i really dislike having these stupid wall warts everywhere. This sort of begs the question of whether the Leviton boxes any smarter about shorted connections. If nothing else, the outlet is properly grounded, and hopefully when they designed the USB side of the circuit they took advantage of having a proper ground wire nearby. They were at least smart enough to support 2A charging on both Apple and everything else.

(That said, there's no externally visible fuse. Hmm.)
Grounding is easily tested with a multimeter and an uninstalled outlet module.

Excess current draw response can be tested with a current meter and a variable test load. Maximum wattage is circa ten watts so a handful of resistors can be incrementally combined to monitor response.

My guess/expectation would be that it either crowbars down to a minimal current upon overload or it limits current at some max level and degrades voltage to maintain that max current.

i would not expect the USB output to blow an internal fuse, but that is certainly possible. This used to be a common problem on early generation computer main boards with 500mA USB ports. Once the fuse blew, the port never had power again until repaired or replaced.

I have a different brand combo USB with AC outlet and it simply limits at 1.1 Amps and 5 volts. Further load demand causes voltage decline while maintaining max current. I only did superficial testing in an attempt to allow 2 Amp charging of my iPad.