Boston ? Like callers dialing 911 and getting no answer, boaters could end up stranded — or worse — if they haven’t upgraded their emergency distress beacons by this weekend. But the improved technology will speed rescues and spare agencies from many false alarms.

Beginning Sunday, the National Oceanic and Atmospheric Administration will stop using its satellites to monitor the 121.5 MHz frequency used by older analog boater distress beacons.

NOAA and the U.S. Coast Guard, which responds to maritime distress calls, will instead limit their watch to newer digital signals coming across the 406 MHz frequency.

The signals come from devices known as Emergency Position Indicating Radio Beacons, or EPIRBs (pronounced EE’-purbs). Signals to NOAA satellites from such devices have been used to rescue more than 11,000 people since the program began in 1982.

For recreational boaters, EPIRBs are not mandatory equipment like life vests, but they are considered a good idea for anyone boating alone or beyond the sight of land. They are required in commercial vessels operating more than three nautical miles offshore.

As with the switchover to digital TV this year, the changeover to digital EPIRBs has been in the works for years. Analog beacons have been banned from sale for the past two years, and NOAA and Coast Guard officials hope the lengthy transition period and a public awareness campaign about the Feb. 1 changeover have delivered the message.

“More and more recreational boaters have the digital ones,” said Lake Erie fishing guide Pat Chrysler, who operates a charter boat in Ohio. “All of us passenger-carrying boats have had them for six years now.”

Anyone calling for help with an older EPIRB after today might still get help if their signal is picked up by a passing airplane because 121.5 MHz remains an aviation distress channel. But without the satellite monitoring of that channel, recreational boaters with an old beacon won’t get the response they’ve come to expect.

“The danger is that people who are in need of a rescue won’t get it,” said Chris Edmonston, director of boating safety for BoatU.S., an organization representing 600,000 boat owners nationwide.

“You’re always going to have some people who don’t know,” Edmonston said. “The problem comes with people who don’t go out that often.”

The switch is a boon for rescuers, though. They have responded to thousands of false alarms generated by microwave ovens, ATMs, sports scoreboards and other sources of analog electronic clutter. Currently, only two in 1,000 of the analog alerts are real.