NEW YORK — Starting this morning and going into the night, TV stations across the U.S. are cutting their analog signals today, ending a six-decade era for the technology and likely stranding more than 1 million unprepared homes without TV service.

The Federal Communications Commission put 4,000 operators on standby for calls from confused viewers, and set up demonstration centers in several cities. Volunteer groups and local government agencies were helping elderly viewers set up digital converter boxes that keep older TVs functioning.

A survey sponsored by broadcasters showed Americans are well aware of the analog shutdown, thanks to a yearlong barrage of TV ads. But not everyone was sure exactly what it means, or what needs to be done to tune in to digital TV.

Any sets hooked up to cable or satellite feeds are unaffected. Newer, digital TVs that get broadcasts through antennas — and older sets hooked up to converter boxes — should be fine, but they will need to be set to "re-scan" the airwaves, to find stations that move to new frequencies today.

Some people might also need new antennas, because digital signals travel differently than analog ones.