Medium-voltage electric power lines might be a new way to bring high-speed Internet access to businesses and homes. Cisco Systems is backing a start-up named Amperion that is developing technology for carrying Net data through the medium-voltage lines linking power substations to neighborhood transformers -- a distinctly different approach than low-voltage networking intended for connecting computers within office buildings and houses. Medium-voltage lines could provide immediate broadband service in areas not now served by DSL or cable modem connections, although providers would still need to come up with a "last mile" solution for hooking up individual subscribers to the neighborhood transformer. That connection could be through cable or phone lines, or even wireless. Amperion expects to start field tests early next year.