RALEIGH, N.C. — Many people say cellular phones make business and everyday life more convenient, but when the phone goes dead, we wonder what went wrong. One company uses a station wagon to keep tabs on its wireless network.

Tim Urton, an engineer for

Verizon

, drives more than 80,000 miles a year testing the network. Fifteen antennas sprout from his station wagon. While traveling around the Carolinas, they transmit and receive special cell phone signals.

"This allows us to improve our service. Where we have problems, it allows us to build towers where we find holes in our service," he said.

Other wireless providers do similar testing because service is what keeps customers. The antennas are just a part of a $250,000 road machine.

Eight cell phones check signals from Verizon and its competitors. The recorded voices are analyzed by computers in Charlotte, letting engineers know how well people will hear on their phones. Two laptop computers keep track of the car's location and problem spots.

"If there's a dropped call or if there's a problem getting on the system, we can look at it and determine exactly where it took place," Urton said.

Officials say more than 134 million Americans have cell phones and that number is growing quickly.