In article .com,
"Mark" wrote:

And there is a REAL reason for the fuses. The bulbs are all low
voltage and wired in series

What you describe is MINIATURE lights, not the "C9" variety being discussed.

when a single bulb fails open all the lights would go out EXCEPT they
have a special device that when a bulb fails open the full voltage
is applied across the failed bulb

It is called a "shunt".

if enough bulbs fail, they will all begin to fail and when they all
short, you will have one big short, hence you need a fuse that is
rated to protect the wire that the string is made out of, not the 15
or 20 Amps that your breaker is rated at..

Your theory is sound, if extremely unlikely. Assuming enough MINIATURE lamps
in a single string open (burn out), and all the shunts work properly
(virtually impossible) to accomplish the short you describe, the small gauge
wire comprising the string itself would ahem open, which would be sufficient
overcurrent protection for me.

The odds of this happening, INDOORS, on a REAL tree, are such that, after my
house burned down, I would go to a casino and hit it big enough to pay for the
rebuild. Problem solved. big grin
--
JR