EXPLAINER: Will burglar alarms still work after 3G shutdown?

AARP, the advocacy group for adults over 50, is also concerned that users of medical alert systems — those necklaces and bracelets, like Life Alert — that connect users to emergency call centers won’t know their gadgets don’t work anymore or won’t be able to replace them in time.

Check your phone to make sure it will still work. Here’s an AT&T list of devices that the carrier says will work normally after Feb. 22. Call the companies that make or service your burglar and fire alarms and personal medical alert systems to see if any need an update. If so, schedule a service visit immediately or get a new device shipped.

OK, DONE. ANYTHING ELSE I SHOULD WORRY ABOUT?

A few. One manufacturer of ankle bracelets for people on probation, parole or pre-trial release said it hasn’t been able to update many 3G-reliant devices. A premature shutdown could potentially allow tens of thousands of offenders like child abusers, sex offenders and drunk drivers to go unmonitored while out of prison, Alcohol Monitoring Systems wrote in an August FCC filing. The company did not respond to questions.

Zonar, which provides GPS and other services for buses and trucks, says tens of thousands of vehicles will be affected. Trucks that aren’t upgraded may have to be idled if drivers can’t electronically log their hours as federal rules require. Zonar has a workaround for the trucking industry, but not all customers have placed orders for it, said Susan Corscadden, a company marketing executive.