Car x-ray.

iStockphoto.com/Evgeny Kuklev

­When Dale Earnhardt Jr. finished a disappointing 23rd in the 2008 3M Performance 400, many fans assumed he'd just been out-driven by Kyle Busch. Earnhardt Jr. had collided with a wall. He was tired. The car had been having problems.

For fans that had scanners, though, it was an entirely different race. At least one commentator, David Kingsley, used a scanner to listen in on the often-frustrated communications between Earnhardt Jr. and his longtime pit chief (and cousin) Tony Eury Jr. Kingsley's verdict? The 23rd-place finish was the fault of poor communications [source: Kingsley].

­Scanners reveal the human element still very much at work in stock car racing. A good scanner lets you be a fly on the wall in your favorite driver's car. You tune to his or her radio frequency, and presto -- you can overhear all the conversations with the pit chief. You're the first to know about mechanical problems. You're privy to all the split-second decisions that go into the race strategy. And if there's a crash, you get a firsthand account while the rest of the fans are still straining to see through the smoke.

A good scanner doesn't stop there, however. Many also let you listen to track workers' communications and receive late-breaking weather updates. Some even hook up to your computer for extra information and features from the Internet. It's no wonder scanners are must-have accessories for die-hard stock car fans.

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