Christmas tree lights are either stacked (like the white plugs in photo) or end to end, also called string to string (like the green plugs). Check the boxes of lights before you buy to make sure they're all compatible. By using stacked plugs, you can join more strands than you can with end-to-end type plugs. Be sure to check the box for the manufacturer's recommendations, however. Usually you can string together three 100-light strands or six 50-light strands.

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Note added at 27 mins (2010-05-31 09:28:16 GMT)
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postoje i lanci bez priključka na struju:
A prelit tree is a convergent product of Christmas lights and Artificial Christmas tree. The product is an artificial fir tree that comes pre-wired and strung with lights, which cannot be removed and are usually embedded within the artificial branches. The product can be sold as a kit - the user assembles the tree and plugs it into an electrical outlet - or the dealer may assemble it before the sale. Prelit trees may have traditional mini bulb lights, LED lights, or fiber-optic lights. Larger trees usually contain traditional strands of bulb lights while smaller tabletop trees have fiber optic branches. Some more expensive trees come with energy-efficient LED lights. Prelit trees are being classified into the categories of electrical products.

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Note added at 28 mins (2010-05-31 09:29:27 GMT)
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pa da ove i nemaju kabela za ušrekati u struju; nekakve samosvijetleće, jer njem. izraz govori o jednostavnoj montaži bez uključivanja u utičnicu (struju)

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Note added at 30 mins (2010-05-31 09:31:18 GMT)
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dakle: nekakvi lanci žaruljica (žaruljice u nizu) bez priključivanja u struju


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Note added at 35 mins (2010-05-31 09:35:36 GMT)
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Božićno drvce s ugrađenim lampicama (svjećicama ili žaruljicama) - valjda se radi o tome; u svakom slučaju da se ne mora trošiti utičnice za ovu trivijalnu "potrebu"