Many of the Illawarra householders who will be among the first on the National Broadband Network will be connected via overhead wires hanging from power poles rather than the underground cables they had expected.Yesterday at Kiama Downs, contractors were installing fibre-optic cable on the power poles on the street.Resident Mark Whalan said his main concern was fast broadband connection speeds but he had also understood that the cables would be placed underground."My query is: how secure is that optical fibre?" he said. "Part of the point of digging a hole is that it's secure."NBN Co spokeswoman Peta Fitzgerald said the area would have half-underground, half-overhead cables."Within the first release sites, NBN Co is committed, wherever possible, to maximising the use of existing infrastructure to build the network," she said. "This generally means that if there is overhead power infrastructure, the local fibre-optic cable is placed overhead on power poles. If there is underground power, the cable is placed in underground conduit."Opposition communications spokesman Malcolm Turnbull visited Barrack Heights yesterday and addressed a backyard gathering at Liberal Party activist Kellie Marsh's house.Mr Turnbull said he advocated a two-tiered system where town centres received download speeds up to 100 megabits per second, but suburbs were slower.He could see reasons why businesses might need 100Mbps but could not think of an application where a household would need such speeds."Obviously, if you've got a business with 50 people using computers at the same time, it's a different thing," he said. "There's no point building infrastructure to people's homes at enormous expense that does not give them additional benefit."It's like a guy that's living out on the bush somewhere ... at the end of a dirt track."He'd love the council to seal it. Now the council can seal it, and then he'd be sweet. Or the council could build a six-lane freeway, and he'd also be sweet. But there would be no material benefit at all between the sealed single-lane road and the six-lane freeway."