Since many of the low-power TV stations continued to broadcast in analog for a while, consumers who watch low-power stations needed an adapter with an analog passthrough feature that allows the viewer to watch both digital and analog signals. Viewers who watch broadcast television on older analog TV sets must use a digital converter box.

On June 12, 2009, all full-power analog television transmissions ended in the United States. Because the DTV transition did nothing to reduce the number of broadcast television system standards (and in fact further complicated them), and due to varying frequency allocations and bandplans, there are many other combinations specific to other countries. In North America and South Korea, these ATSC tuner boxes convert from ATSC to NTSC, while in most of Europe and other places such as Australia and most Asian countries, they convert from Digital Video Broadcasting (DVB) to PAL, and in Japan, the Philippines and most countries in South America, they convert from ISDB-T to either NTSC or PAL. It normally does not refer to satellite TV, which has always required a set-top box either to operate the big satellite dish, or to be the integrated receiver/decoder (IRD) in the case of direct-broadcast satellites (DBS). The input digital signal may be over-the-air terrestrial television signals received by a television antenna, or signals from a digital cable system. Some also have an HDMI output since some TVs with HDMI do not have a digital tuner. A digital television adapter ( DTA), commonly known as a converter box or decoder box, is a television tuner that receives a digital television (DTV) transmission, and converts the digital signal into an analog signal that can be received and displayed on an analog television set.

Zenith digital to analog tv converter