Digital to analog converter box

HowStuffWorks

As important as television is to many people in the United States, the technology behind the medium hasn't changed that much since its introduction. Early television began in the 1870s, but TV didn't really catch on until the introduction of electronic television in the early 20th century. Though there were regular broadcasts, people at large didn't adopt television until after World War II. In 1945, there were only nine commercial TV stations broadcasting, but by 1949, there were 48. And by 1960, there were 515 commercial stations, with TVs in 85 percent of American homes [source: Federal Communications Commission (FCC)].

Color TV was around as early as 1946, when CBS engineer Peter Goldmark -- who also had a hand in creating the long-playing vinyl record -- developed a method of broadcasting in color. Unfortunately, his color-broadcasting standard wasn't compatible with existing TV sets, and in 1953, the National Television Standards Committee (NTSC) adopted RCA's method of color broadcasting instead.

From there, we have incremental introductions -- the remote control, cable and satellite providers, and videocassette recorders (VCRs), et cetera. But in general, you don't have to have all those things to watch TV. If you live in an area near a broadcast station, you can still plug a pair of rabbit ears into the antenna jack on the back of your set and get programming.

On Feb. 17, 2009, some analog channels in the United States went dark -- with a few exceptions, the rest did so on June 12. Regular broadcasters in the United States have completed the transition to digital television (DTV). The reason? Broadcasters moved their signals to another part of the radio spectrum. One reason for the switch was to free up space for police, fire and other public safety communications. The remaining portion of the broadcast signal will be available to consumers for wireless services.

The original date for the analog-to-digital transition had to be moved because the FCC needed to raise awareness of the change among the population. The idea was to make sure few people are left behind, but their efforts  caused some confusion. To receive digital television signals, some people need a converter box.

If you live in the United States and use a regular antenna to get television signals over the air, this is probably the reason why you can't see your old stations today.

­ ­