Jun. 10--All major broadcast television stations in the Bay Area and nationwide on Friday will turn off their analog signals and send only the digital ones they are already transmitting. Many stations will also change the channels on which they broadcast their digital signals.

Two local stations -- KNTV Ch. 11 and KSTS Ch. 48 -- will turn off their analog broadcasts just after noon. The others will switch off their analog signals after 11 p.m. Five stations -- KICU (Ch. 36, previously analog Ch. 52), KOFY, KCNS, KQET and KFTY -- turned off their analog signals earlier this year.

Here are some answers to frequently asked questions about the shift to digital:

Q Wasn't this supposed to happen in February?

A Yes. But nearly 6 million households nationwide, about 5 percent of the total, were unprepared for the transition because they neither subscribed to a pay television service nor had a TV connected to a digital tuner. Congress and the president delayed the switch to try to give consumers more time to get prepared. But it's estimated that more than 60,000 households in the Bay Area still are not ready for the change.

Q Why is this happening?

A Digital signals offer clearer pictures and make more efficient use of the airwaves. In the same space that broadcasters used to transmit one analog channel, they can send out multiple digital ones. That gives consumers

more channel choices of channels and lets the government reclaim some of the airwaves for use by emergency services and new commercial communication services.

Q How do I prepare for the change?

A If you use an antenna to get television signals, you'll need to have a device that can tune in the new digital transmissions. Among the devices with digital broadcast (ATSC) tuners are new televisions, some recording devices such as DVD recorders, and digital converter boxes. If you've bought a television in the last two years, it likely has a digital tuner. You may also need to upgrade your antenna.

If you get local TV channels through a pay television service such as Comcast cable or Dish Network -- and all your televisions are connected to the service -- then you won't need to do anything. At least for now, Comcast will be converting the local stations' over-the-air digital signals to analog ones that it sends over its cable wires so that customers with older televisions can continue to tune them in without any additional equipment.

Q I've got a digital converter box or television and I'm not having any reception issues getting the new digital stations. I'm all set, right?

A No.