A set-top box that converts over-the-air digital TV broadcasts to analog for TV sets that accept only analog input (NTSC, PAL). It transforms digital broadcasts in standard definition (SD) and high definition (HD) to analog. Also called a "DTV, ATSC, digital or set-top converter box," "D/A converter" (DAC) or "digital TV adapter" (DTA). See digital TV transition.

Analog Pass Through
Some 7,000 low-power TV stations in the U.S. are not required to switch to digital in 2009, and TV converter boxes may have an "analog pass through" capability that lets the viewer switch between analog and digital signals. At the end of their call signs, low-power stations have low power (LP) and Class A (CA) acronyms; for example, WWJT-LP and WTSD-CA. They may also start with K or W, followed by channel number; for example, W35BT and K36DC.

If viewers with analog TVs watch low-power analog and digital TV without the pass-through feature on the converter box, the antenna cable can be split into the antenna jacks on the TV and the converter box. The converter box is then cabled to the TV's A/V input jacks (RCA), and the TV is switched from antenna to A/V input to change from analog to digital and vice versa.