A digital TV decoder, sometimes called a digital TV tuner, converts digital signals into analog signals. This technology allows information to be received digitally but viewed on televisions that are not equipped with digital capabilities. Digital broadcasting uses radio frequency (RF) to transmit computer code that is then decoded and displayed on a television.

In 1996, the U.S. Congress passed a law that gave additional broadcast channels to each TV station so that they could begin broadcasting in digital as well as analog. As of 13 June 2009, all television signals in the United States were required to be broadcast in digital, thereby making some older television sets obsolete. The digital TV decoder, also known as a digital television adapter (DTA), digital-to-analog converter box, or converter box, collects the digital signals from the airwaves and translates them for use on a non-digital television.

Not all decoders are set-top boxes, though. Most newer televisions have the decoder built-in, and therefore eliminate the need for a converter box. Digital TV decoders, however, will not convert analog TV into high definition (HD) though some set-top boxes will.

In the US, the government made the decision to switch to all-digital broadcasting in an effort to free up parts of the broadcast spectrum for use by public safety departments. They also intended to auction off unused portions of the spectrum to wireless companies for uses such as wireless broadband. Another anticipated benefit to consumers is that TV stations will be able to offer improved sound and picture quality, much better than the former analog process could.

Hooking up a digital TV decoder to an analog television set will require a television antenna. The antenna wires will be connected to the back of the converter box in the jack, or screws, labeled “antenna.” The converter box must then be connected to the television. Most digital TV decoders offer either red, white and yellow RCA jacks, or a screw-in type coaxial cable. Whichever method a particular digital TV decoder is designed to accommodate, the cables will need to be connected into the related TV input. Finally, the decoder must be plugged into the wall and powered on.

Digital TV decoders that use RCA inputs will require the TV to be set to the auxiliary input channel, or if coaxial cables are used, the television will have to be tuned to channel three or four. The remote control associated with the digital TV decoder must be used, as opposed to the regular TV remote, but, the television remote control will be required to adjust the volume and to turn the TV on and off.