HONOLULU — At noon sharp Thursday in Hawaii, a message appeared on analog TV sets across the islands: “All full power Hawaii TV stations are now digital.”

The state shut down old-fashioned broadcast signals, more than a month before the rest of the country is set to make the now-contentious switch.

Even before the change, residents lit up special TV help center phone lines set up by the Federal Communication Commission and broadcasters. More than 300 calls came in Wednesday, and 10 lines were lighting up Thursday.

On home screens, the shutdown message flashed for about a minute in white text on a blue background. Then, a seven-minute announcement video began a broadcast loop that will continue for several weeks on major island stations.

Technicians are calling it the “analog night light.”

Officials at the call center made last-minute checks with about 20 TV stations around the islands, with all reporting they were ready.

“The calls we’re getting now are from those people who are waking up and saying, ‘Oh my God, what do I do?’” said Lyle Ishida, the FCC’s Hawaii digital TV project manager, just before the switch.

Experts taking the calls quickly screened out anyone with cable or satellite service, because they are unaffected by the switch. But some confusion had been expected.

“No matter how many commercials we run, there will always be a certain part of the population that doesn’t get the message,” said Chris Leonard, the president of the Hawaii Association of Broadcasters, who was helping out at the call center.

One glitch cropped up even before the switch, with the PBS station on the Big Island reporting it hadn’t yet received equipment to send its digital signal to an area of the island that is the southernmost point in the nation, South Point.

PBS has been the only station serving the rural area. The problem was expected to last for several days.

Another station on the Big Island, ABC affiliate KITV, reported a mechanical problem in its digital transmitter that delayed the transition.

With analog TV signals turned off, residents with older TVs were finding out whether they will be missing any channels or whether they still have any service at all.

Government officials and broadcasters estimate about 20,000 households in Hawaii still get their TV signals over the air, meaning they’d have to buy new TVs with digital tuners or digital converter boxes for their old TVs.

“It’s really amazing how many people wait until the last minute,” said June Gonzales, a member of the FCC team.