But consumers who have cable or satellite service generally do not need a built-in tuner because that function is provided by a separate decoder box.

Most of those services only work if the phones are connected to a special decoder box plugged into a high-speed Internet modem.

Viewers without decoder boxes saw a scrambled, flickering picture and garbled or substituted audio.

With satellite, each TV set requires its own decoder box; those boxes can cost hundreds of dollars each.

It requires an Ambisonic decoder box at the replay end, and there are few commercial decoder manufacturers.

Surround-sound requires a decoder box; in Proton's 31-inch and 27-inch sets this is built in.

To keep down the price, most digital TV's require an additional set-top decoder box that costs from $550 to $1,000.

Tony Boyd, a retail store planner in Dallas, has no problem receiving digital broadcast channels with his decoder box and an antenna.

A decoder box was required to unscramble the signal and permit normal viewing.

People who already have a multichannel home-theater system would need a decoder box for the new format, which would probably cost several hundred dollars.