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An automatic channel memory system (ACMS) is a system in which a digitally controlled radio tuner such as a TV set or VCR could search and memorize TV channels automatically. While more common in television, it can also be used to store presets for radio stations. This is often called a channel scan, though that may also refer to a "preview" mode which plays each station it finds for a few seconds and then moves on to the next, without affecting memory.
A typical TV device allows an automatic channel scan to be performed from a menu accessed by a button on the TV set, or sometimes only on the remote control. This applied first to analog TV sets — sometimes those with digital LED displays, or later always those with on-screen displays. These simply searched for the video carrier signal on every channel. (Before the advent of ACMS, many sets would search for the next channel every time it was changed.)
It now also applies to digital TV, which must not only find the signal itself, but also decode its metadata enough to remap channel numbers to their proper locations. In the case of the American ATSC system, the ATSC tuner uses PSIP metadata to do this. The internal channel map for digital TV stations is different from the presets or "favorites" that the user has programmed. Just as with analog TV (which worked only by turning a preset on or off for each station/channel), users of digital television adapters and other similar tuners can choose to ignore channels that are still in the channel map.
Analog station presets and digital channel maps are normally deleted when a new scan is started. On some tuners, digital channel maps can be added-to with an "easy-add" channel scan, which is useful for finding new stations without losing old ones that may be weak or currently off-air, or not aimed-at with an antenna rotator or other set-top TV antenna adjustment. If a station adds a digital subchannel, most digital TV tuners will find it automatically as soon as the user turns to another channel that is carried by that station, adding it to the channel map.
Many will also automatically add a new digital station's subchannels by tuning manually to the station's physical channel, though if this conflicts with the virtual channel number of another station, a complete re-scan may be the only solution. (Choosing an unused subchannel number [i.e. 30.99] on that major channel number [i.e. 30] may avoid the remap on existing subchannels [i.e. 30.1] and force the tuner to listen on that physical channel.) This has often happened in the U.S., where stations (especially LPTV) find it easiest to place their digital operations on a vacated analog channel.
The same problem also occurs when the same station moves its digital transmission back to its old analog channel. There is no way to delete a station from the internal channel map, and a re-scan may be needed; or if the new physical channel is found, it may leave the old mapping in place, causing duplicate channels that cannot be accessed through direct entry of the numbers without also pressing the channel-up/down buttons.
Many modern TV sets do an ACMS scan automatically as part of the setup process the user is guided through when the device is initially plugged-in. While early sets often lost their memory in a power outage or by otherwise being disconnected from mains electricity, all of them now have non-volatile RAM or a backup of some sort.
Digital television (DTV) is the transmission of television audiovisual signals using digital encoding, in contrast to the earlier analog television technology which used analog signals. At the time of its development it was considered an innovative advancement and represented the first significant evolution in television technology since color television in the 1950s. Modern digital television is transmitted in high-definition television (HDTV) with greater resolution than analog TV. It typically uses a widescreen aspect ratio in contrast to the narrower format of analog TV. It makes more economical use of scarce radio spectrum space; it can transmit up to seven channels in the same bandwidth as a single analog channel, and provides many new features that analog television cannot. A transition from analog to digital broadcasting began around 2000. Different digital television broadcasting standards have been adopted in different parts of the world; below are the more widely used standards:
Terrestrial television is a type of television broadcasting in which the television signal is transmitted by radio waves from the terrestrial (Earth-based) transmitter of a television station to a TV receiver having an antenna. The term terrestrial is more common in Europe and Latin America, while in Canada and the United States it is called broadcast or over-the-air television (OTA). The term "terrestrial" is used to distinguish this type from the newer technologies of satellite television, in which the television signal is transmitted to the receiver from an overhead satellite; cable television, in which the signal is carried to the receiver through a cable; and Internet Protocol television, in which the signal is received over an Internet stream or on a network utilizing the Internet Protocol. Terrestrial television stations broadcast on television channels with frequencies between about 52 and 600 MHz in the VHF and UHF bands. Since radio waves in these bands travel by line of sight, reception is generally limited by the visual horizon to distances of 64–97 kilometres (40–60 mi), although under better conditions and with tropospheric ducting, signals can sometimes be received hundreds of kilometers distant.
Advanced Television Systems Committee (ATSC) standards are an American set of standards for digital television transmission over terrestrial, cable and satellite networks. It is largely a replacement for the analog NTSC standard and, like that standard, is used mostly in the United States, Mexico, Canada, and South Korea. Several former NTSC users, in particular Japan, have not used ATSC during their digital television transition, because they adopted their own system called ISDB.
Digital cable is the distribution of cable television using digital data and video compression. The technology was developed by General Instrument. By 2000, most cable companies offered digital features, eventually replacing their previous analog-based cable by the mid 2010s. During the late 2000s, broadcast television converted to the digital HDTV standard, which was incompatible with existing analog cable systems. In addition to providing higher resolution HD video, digital cable systems provide more services such as pay-per-view programming, cable internet access and cable telephone services. Most digital cable signals are encrypted, which reduced the incidence of cable television piracy which occurred in analog systems.
A tuner is a subsystem that receives radio frequency (RF) transmissions and converts the selected carrier frequency and its associated bandwidth into a fixed frequency that is suitable for further processing, usually because a lower frequency is used on the output. Broadcast FM/AM transmissions usually feed this intermediate frequency (IF) directly into a demodulator that converts the radio signal into audio-frequency signals that can be fed into an amplifier to drive a loudspeaker.
WIRE-CD, virtual and UHF digital channel 33, is a low-powered, Class A television station licensed to Atlanta, Georgia, United States. Its analog broadcast range reached into the inner suburbs. Previously an MTV2 affiliate, programming since digital conversion now consists entirely of infomercials. As WIRE-LP, like most over-the-air MTV2 network affiliates, it was an affiliate of The Box until that network's acquisition by Viacom in 2001. Owned by Viacom, MTV2 is one of the few cable networks that can be seen over the air.
Datacasting is the broadcasting of data over a wide area via radio waves. It most often refers to supplemental information sent by television stations along with digital terrestrial television, but may also be applied to digital signals on analog TV or radio. It generally does not apply to data which is inherent to the medium, such as PSIP data which defines virtual channels for DTT or direct broadcast satellite systems; or to things like cable modem or satellite modem, which use a completely separate channel for data.
Guide Plus+, TV Guide On Screen, TV Guide Daily, TV Guide Plus+ and Guide Plus+ Gold or G-Guide are brand names for an interactive electronic program guide (EPG) system that is used in consumer electronics products, such as television sets, DVD recorders, personal video recorders, and other digital television devices. It offers interactive on-screen program listings that enable viewers to navigate, sort, select and schedule television programming for viewing and recording. The differing names are only used for marketing purposes – the entire system is owned by Rovi Corporation, the successor to Gemstar-TV Guide International. In 2016, Rovi acquired digital video recorder maker TiVo Inc., and renamed itself TiVo Corporation.
An ATSCtuner, often called an ATSC receiver or HDTV tuner, is a type of television tuner that allows reception of digital television (DTV) television channels that use ATSC standards, as transmitted by television stations in North America, parts of Central America, and South Korea. Such tuners are usually integrated into a television set, VCR, digital video recorder (DVR), or set-top box which provides audio/video output connectors of various types.
In broadcasting, digital subchannels are a method of transmitting more than one independent program stream simultaneously from the same digital radio or television station on the same radio frequency channel. This is done by using data compression techniques to reduce the size of each individual program stream, and multiplexing to combine them into a single signal. The practice is sometimes called "multicasting".
A digital channel election was the process by which television stations in the United States chose which physical radio-frequency TV channel they would permanently use after the analog shutdown in 2009. The process was managed and mandated by the Federal Communications Commission for all full-power TV stations. Low-powered television (LPTV) stations are going through a somewhat different process, and are also allowed to flash-cut to digital.
A multiplex or mux is a grouping of program services as interleaved data packets for broadcast over a network or modulated multiplexed medium. The program services are split out at the receiving end.
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. Some also have an HDMI output since some TVs with HDMI do not have a digital tuner. The input digital signal may be over-the-air terrestrial television signals received by a television antenna, or signals from a digital cable system. 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).
A coupon-eligible converter box (CECB) was a digital television adapter that met eligibility specifications for subsidy "coupons" from the United States government. The subsidy program was enacted to provide terrestrial television viewers with an affordable way to continue receiving free digital terrestrial television services after the nation's television service transitioned to digital transmission and analog transmissions ceased. The specification was developed by the National Telecommunications and Information Administration (NTIA), with input from the broadcast and consumer electronics industries as well as public interest groups.
A free-to-air or FTA Receiver is a satellite television receiver designed to receive unencrypted broadcasts. Modern decoders are typically compliant with the MPEG-2/DVB-S and more recently the MPEG-4/DVB-S2 standard for digital television, while older FTA receivers relied on analog satellite transmissions which have declined rapidly in recent years.
In the United States, digital television broadcasts, or DTV, can be received via cable, via internet, via satellite, or via digital terrestrial television — much like analog television broadcasts have been. Full-power analog television broadcasts, however, were required by U.S. federal law to cease by June 12, 2009. Low-power and TV Translator stations were required to cease analog broadcasts on July 13, 2021, with Class A analog stations signing off on September 1, 2015. Also by law, digital broadcasts — when transmitted as over-the-air signals — must conform to ATSC standards. It is unclear whether satellite operators are free to use their own proprietary standards; and many standards exist for Internet television.
Analog passthrough is a feature found on some digital-to-analog television converter boxes. Boxes without analog passthrough only allow digital TV to be viewed on older, analog-only TVs. Those with analog passthrough allow both digital and analog television to be viewed on older TVs.
The digital transition in the United States is the switchover from analog to exclusively digital broadcasting of terrestrial television programming. According to David Rehr, then president and CEO of the National Association of Broadcasters, this transition represented "the most significant advancement of television technology since color TV was introduced." For full-power TV stations, the transition went into effect on June 12, 2009, with stations ending regular programming on their analog signals no later than 11:59 p.m. local time that day.
TV radio, TV band radio, and TV audio radio are common names for a type of radio receiver that can play the audio portion of a TV channel. The actual name of the device may comprise a list of all frequency bands the device can receive, one or two of which includes the TV channel bands.