NEW YORK — When Adele Rothman bought her 16-year-old son a car in 2003, she made sure to pick one that had OnStar, the onboard communications and safety system.

What the Scarsdale, N.Y., resident didn’t know was that the OnStar system in the car was already doomed to die. The federal government decided in 2002 to let cellular carriers shut down analog cell phone networks, used by Rothman’s Saab and about 500,000 other OnStar-equipped cars, after Feb. 18, 2008.

It’s the end of the nationwide network that launched the U.S. wireless industry 24 years ago, and it leaves a surprising number of users including Rothman in the lurch.

OnStar told Rothman in March its service would stop at the end of this year, in anticipation of the network shutdown in February. “I was really upset,” she said, “because that was my tie line” to her son.

Perhaps a million cell phones will lose service, but those are cheap and easy to replace. The effects will be felt the most by people who have things that aren’t phones but have built-in wireless capabilities, such as OnStar cars and home alarm systems.

The shutdown date has been known years in advance, but some industries appear to have a had a problem updating their technologies and informing their customers in advance, which raises the question of whether the effects will be even more widespread the next time a network is turned off, given the proliferation of wireless technology.

General Motors Corp., which owns OnStar, started modifying its cars after the 2002 decision by the Federal Communications Commission to let the network die, but some cars made as late as 2005 can’t use digital networks for OnStar, nor can they be upgraded. For some cars made in the intervening years, GM provides digital upgrades for $15.

In 2006, OnStar said it had let customers know of the shutdown with a posting on its Web site. This year, it said it had notified all affected customers. Spokeswoman Cristi Chojnacki said she was unable to comment beyond those statements. General Motors and other car manufacturers with similar systems, including Daimler AG’s Mercedes-Benz, are facing a potential class-action lawsuit over the analog shutdown.

When Rothman complained, GM sent a $500 coupon toward the purchase of a new car. To compensate for the lack of OnStar, she outfitted her son’s car with a hands-free system and a Global Positioning System.

A week before the end-of-year shutdown, the analog coverage map is still the first one presented on OnStar’s Web site. The digital coverage map, showing large areas of “limited” service in out-of-the-way places, is available on another page.

On the home alarm side, about 400,000 systems still use analog service, said Lou Fiore, chairman of the Alarm Industry Communications Committee. In most of those systems, the wireless link to the alarm center is a backup to the landline. But some homes lack a landline, so the wireless link is the only connection to the outside world.

Fiore doesn’t know the current number of systems that only use analog wireless connections and no landline, but an AICC a few years ago put the number at 138,000.

“The larger (alarm) companies are in pretty good shape,” Fiore said. “There are so many smaller companies out there that are probably, I’d say, in denial. They just don’t know about it.”