On Jan 1, 1:17*am, " wrote:
....you could
be connecting those 'unimportant' three volts to a meter-circuit that
blows it's top at two volts.

yep


A cable track is a little oscillator that puts a warbling TONE on the
wire under test, which you can then 'hear' by waving a matching
receiver at the other end of the wire.

good tip. thanks.

-R.S.Hoover

Mark