They can also be connected between your fingers and the wire to identify the
hot wire in knob-and-tube wiring in the attic where no ground is within
reach. That function is probably not very useful nowadays.
Don Young

"MOP CAP" wrote in message
news:040720051133066260%Pilgrim6nospam@mindspring. com...
In this same vein those neon circuit testers are worthless and
potentially dangerous because they can give erroneous readings.
Capacitive coupling and leakage give these. There was an article in
Electrical Contracting and Maint. several years ago. It's gist was that
they were only good for night lights.

Chuck P.