The National Television System Committee (NTSC) standard for analog television signal broadcasting, adopted by the Federal Communications Committee (FCC) in 1941, remained in place until 2009. In June of that year, the Advanced Television Systems Committee (ATSC) standards for digital television (DTV) broadcasting replaced the NTSC's analog standards for all major television broadcasters in the United States. Because of the difference in the DTV signals, ATSC requires a tuner capable of decoding its signals at the user end of the transmission. In order to facilitate this process, television sets and television interfacing devices, such as digital video disc (DVD) players and digital video recorders (DVR), feature integrated ATSC. Any device incorporating integrated ATSC has an ATSC tuner built into its hardware.
Before a device, such as a high-definition television (HDTV), can display the DTV signal broadcast by a telecommunications company, the signal must first undergo a series of operations. When DTV signals are sent out, they are compressed at the source. Upon reaching their destination, these signals must be decompressed, demultiplexed, demodulated, and error corrected. Each of these processes, along with several others, is the duty of the digital tuner.
DTV signals are compressed into smaller packets of data for easier transport either over the air or through another medium, such as coaxial cable, and therefore need to be decompressed once they reach their destination. Because these signals are combined in an operation called multiplexing, and transported using the moving picture experts group (MPEG) transport stream, they must also be demultiplexed. Demodulation occurs when the tuner transforms the broadcast signal into a signal usable by the television, and error correction is the process of accounting for any missing data in the stream. Another job of the ATSC tuner is to select the proper radio frequency channel.
For owners of older television (TV) sets, particularly those manufactured prior to 2007, the switch to DTV posed a problem when the NTSC standard was abandoned. As of 2007, all TV sets and interfacing devices are required to be manufactured with an integrated ATSC tuner. Older TVs have no way of performing the necessary operations to display DTV signals, and at the time of the switch to ATSC in 2009, consumers with older TV sets faced the necessity of either purchasing a new TV with integrated ATSC or an external converter box. For this reason, coupons were issued to offset the consumer's cost in the purchase of one of these set-top boxes.
Similar to the ATSC tuner is the quadrature amplitude modulation (QAM) tuner. QAM is a standard outside of ATSC and is generally used by cable television broadcasters. Unlike integrated ATSC, QAM tuners are usually integrated into a set-top box provided by cable companies, though some HDTV sets also feature integrated QAM tuners as well.
