The company can cut off the computer's wireless access, but the carrier would still be out a couple of hundred dollars. The buyer would be left with a computer that's fully usable except for cellular broadband.

LM Ericsson AB, the Swedish company that makes many of the modems that go into laptops, announced Tuesday that its new modem will deal with this issue by including a feature that's virtually a wireless repo man. If the carrier has the stomach to do so, it can send a signal that completely disables the computer, making it impossible to turn on.

"We call it a `kill pill,'" said Mats Norin, Ericsson's vice president of mobile broadband modules.

The module will work on AT&T Inc.'s U.S. third-generation network, and on many other 3G networks overseas.

AT&T late last year started subsidizing small laptops known as "netbooks," which normally cost about $400, so that RadioShack Corp. can sell them for $100. The buyer commits to paying $60 per month for two years for AT&T's wireless broadband access. Such offers have become very common in Europe.

It's unlikely that carriers would resort to wielding the "kill pill." But the technology, developed with Intel Corp., has other uses. For instance, a company could secure its data by locking down stolen laptops wirelessly. Lenovo Group Ltd. has said it will build this sort of feature into its laptops.

The new Ericsson modem can also stay active while a computer is off, listening for wireless messages. That means it could wake up and alert the user when it receives an important e-mail, or if someone is calling with a conferencing application like Skype.

Laptop makers that use Ericsson modules include LG Electronics Inc., Dell Inc., Toshiba Corp. and Lenovo.