RPBG has been well discussed in Mike Sokol's forum.
I pissed away too much time and money, two things I don't have enough of, inventing an outlet tester that actually works to measure and detect faulty outlet wiring.
http://www.johnhroberts.com/OD1.htm link to TMI about my outlet tester.
Besides using a NCVT (non contact voltage tester), there are old school techniques that work to some degree. Another old tool a neon lamp probe will generally light if you grasp one lead in your finger and probe the suspect hot lead with the other probe. The typical neon lamp probes have a current limiting resistor in series with the neon bulb.
Another similar old school trick is to use a VOM set to measure voltage. While gripping one probe with your free hand probe with other. A hot outlet pin can measure 50-60V. Of course be extremely careful to make sure you are set for voltage mode. If you accidentally use current mode you could get a shocking result
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I abandoned my outlet tester project 6 years ago or so.... the widespread adoption of GFCI outlets have saved many lives.
JR