The last outdoor Christmas lights came down at our house today
and I thought of a question as I was taking them down.  In
countries where the AC line voltage is 120 volts on a standard
circuit, one very common configuration is 35 incandescent bulbs
in series.  The painted glass envelopes look much like NE2 neon bulbs but
they are actually 3.4 volt incandescent lamps much like 2-cell
flashlight bulbs with each bulb drawing a bit over 400 milliamps.

	I am sure that there is cut-throat competition to
manufacture the strings as cheaply as possible and still pass
safety requirements in the various countries so my question is do
they sell the same configurations only with 6-volt filaments in
240-volt countries or do they simply sell 70-lamp strings instead
of 35-lamp strings as the minimum number of lights in one string?

	Here, you can buy these lights with 70 or more bulbs but
they appear to be 35-light series strings parallelled .  There is
frequently a clear extra bulb with a red tip containing a
thermocouple switch which causes the whole string to blink if you
want it to.  70 or more light strings would need one blinker bulb
per series string.

	Each lamp contains a shunt that falls in place when a
filament burns out so one still sees light from the remaining
working bulbs but lots of luck if one of the sockets becomes
intermittent as the whole string goes dark.  A capacitively
coupled probe might tell you where the break is but a new string
usually fixes the problem much faster.

Martin McCormick WB5AGZ
--=20
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