A metal box by the roadside in my neighborhood has a sign on it:

This is rather nonsensical, since fiber optic cables are made of glass and can't conduct significant amount of electricity. (Sure, one can put a high voltage across the ends of an insulator, but only negligible current flows.) Maybe the scary label is there to deter petty thieves? Perhaps there are some other non-fiberoptic components inside that involve high voltages? But most likely it's just a parsing ambiguity, like the street signs near kindergarten playgrounds that tell passing drivers:

(cf. Achieve New Balance (17 Jul 2002), Mary Landers for Mathias (25 Aug 2002), Oxford Commas (25 Jan 2004), Unfortunate Misparsing (2004-02-27), ... ) - ^z - 2008-05-21

(correlates: Comments on High Voltage Fiberoptic Cable, MaryLandersForMathias, Worse Obsessions, ...)