This article does not cite any references or sources. (December 2006) Please help improve this article by adding citations to reliable sources. Unverifiable material may be challenged and removed.

A subcarrier is a separate analog or digital signal carried on a main radio transmission, which carries extra information such as voice or data. More technically, it is an already-modulated signal, which is then modulated into another signal of higher frequency and bandwidth. This is an early and simple method of multiplexing. Image File history File links Question_book-3. ... An analog or analogue signal is any continuously variable signal. ... The term digital signal is used to refer to more than one concept. ... In communications, transmission is the act of transmitting electrical messages (and the associated phenonomena of radiant energy that pass through media). ... The word voice can be used to refer to: Sound: The human voice. ... For other uses, see Data (disambiguation). ... In telecommunications, modulation is the process of varying a periodic waveform, i. ... In information theory, a signal is the sequence of states of a communications channel that encodes a message. ... For other uses, see Frequency (disambiguation). ... Bandwidth is the difference between the upper and lower cutoff frequencies of, for example, a filter, a communication channel, or a signal spectrum, and is typically measured in hertz. ... In telecommunications, multiplexing (also muxing or MUXing) is the combining of two or more information channels onto a common transmission medium using hardware called a multiplexer or (MUX). ...

FM stereo

Stereo broadcasting is made possible by using a subcarrier on FM radio stations, which takes the left channel and "subtracts" the right channel from it — essentially by hooking up the right-channel wires backward (reversing polarity) and then joining left and reversed-right. The result is modulated with AM, more correctly called sum and difference modulation or SDM, at 38 kHz in the FM signal, which is joined with the mono left+right audio (which ranges 50Hz~15 kHz). A 19 kHz low deviation pilot tone is also added at a low modulation percentage to trigger radios to decode the stereo subcarrier, making FM stereo fully compatible with mono. FM radio is a broadcast technology invented by Edwin Howard Armstrong that uses frequency modulation to provide high-fidelity sound over broadcast radio. ... A radio station is an audio (sound) broadcasting service, traditionally broadcast through the air as radio waves (a form of electromagnetic radiation) from a transmitter to an antenna and a thus to a receiving device. ... The polarity of an object is, in general, its physical alignment of atoms. ... Amplitude modulation (AM) is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. ... A kilohertz (kHz) is a unit of frequency equal to 1,000 hertz (1,000 cycles per second). ... This article is about the SI unit of frequency. ... A kilohertz (kHz) is a unit of frequency equal to 1,000 hertz (1,000 cycles per second). ... In telecommunication, a pilot is a signal, usually a single frequency, transmitted over a communications system for supervisory, control, equalization, continuity, synchronization, or reference purposes. ...

Once the receiver demodulates the L+R and L−R signals, it adds the two signals ((L+R) + (L−R) = 2L) to get the left channel and subtracts ((L+R) − (L−R) = 2R) to get the right channel. Rather than having a local oscillator, the 19 kHz pilot tone provides an in-phase reference signal used to reconstruct the missing carrier wave from the 38 kHz signal. Demodulation is the act of removing the modulation from an analog signal. ... The Superheterodyne receiver (or to give it its full name, The Supersonic Heterodyne Receiver – usually these days shortened to superhet) was invented by Edwin Armstrong in 1918. ... This article or section does not adequately cite its references or sources. ...

For AM broadcasting, different analog (AM stereo) and digital (HD Radio) methods are used to produce stereophonic audio. Modulated subcarriers of the type used in FM broadcasting are impractical for AM broadcast due to the relatively narrow signal bandwidth allocated for a given AM signal. On standard AM broadcast radios, the entire 9 kHz to 10 kHz allocated bandwidth of the AM signal may be used for audio. AM broadcasting is radio broadcasting using Amplitude Modulation. ... AM stereo is any of a number of mutually-incompatible techniques for broadcasting two_channel audio in the mediumwave band in a manner that is compatible with receivers designed for standard amplitude modulation. ... HD Radio is an in-band on-channel (IBOC) digital radio system created by iBiquity for broadcasting via existing FM and AM radio stations. ...

Television

Likewise, TV signals are transmitted with the black and white luminance part as the main signal, and the color chrominance as the subcarriers. A black and white TV simply ignores the extra information, as it has no decoder for it. To reduce the bandwidth of the color subcarriers, the sampling rate for color information is reduced four-to-one by using only every other pixel on every other scan line. (This is made possible by the fact that the human eye sees much more detail in contrast than in color.) In addition, only blue and red are transmitted, with green being determined by subtracting the other two from the luminance and taking the remainder. (See: YIQ, YCbCr, YPbPr) Various broadcast television systems use different subcarrier frequencies, in addition to differences in encoding. TV redirects here. ... A photograph of a sign in grayscale The same photograph in black and white Monochrome comes from the two Greek words mono (μωνο, meaning one), and chroma (χρωμα, meaning surface or the color of the skin). A monochromatic object has a single color. ... As applied to analog television signals, two different words are used, luminance and luma, meaning two different things. ... Chrominance (chroma for short) comprises the two components of a television signal that encode color information. ... The sampling frequency or sampling rate defines the number of samples per second taken from a continuous signal to make a discrete signal. ... This article is about the picture element. ... A scan line is one line, or row, in a raster scanning pattern, such as a video line on a Cathode ray tube (CRT) display of a television or computer. ... This article is about modern humans. ... For other uses, see Eye (disambiguation). ... Look up Contrast in Wiktionary, the free dictionary. ... In mathematics, the result of the division of two integers usually cannot be expressed with an integer quotient, unless a remainder —an amount left over— is also acknowledged. ... This article needs to be cleaned up to conform to a higher standard of quality. ... A colour image and the Y, Cb and Cr elements of it. ... YPbPr (also referred to as YPrPb, PrPbY, and PbPrY) is a color space used in video electronics. ... There are several broadcast television systems in use in the world today. ... An encoder is a device used to encode a signal (such as a bitstream) or data into a form that is acceptable for transmission or storage. ...

Subcarriers on the video can also carry three audio channels, including one for stereo (same left-minus-right method as for FM), another for second audio programs (such as descriptive video service for the vision-impaired, and bilingual programs), and yet a third hidden one for the studio to communicate with reporters or technicians in the field (or for a technician or broadcast engineer at a remote transmitter site to talk back to the studio), or any other use a TV station might see fit. Second[ary] audio program[ming] (SAP) is an auxiliary audio channel for television that can be broadcast or transmitted both over the air and by cable TV. It is often used for an alternate language (hence giving the facetious Spanish audio program expansion to the acronym), or for the Descriptive... The Descriptive Video Service (DVS), created by WGBH-TV in Boston [citation needed], is used by the Public Broadcasting Service (PBS) in the U.S. to provide video description for the visually impaired, so they can better understand what is happening on the video portion of the program. ... A technician is generally someone in a technological field who has a relatively practical understanding of the general theoretical principles of that field, e. ... Broadcast engineering is the field of electrical engineering, and now to some extent radio and television broadcasting. ... Antenna tower of Crystal Palace transmitter, London A transmitter is an electronic device which, usually with the aid of an antenna, propagates an electromagnetic signal such as radio, television, or other telecommunications. ... A television station is a type of radio station that broadcasts both audio and video to television receivers in a particular area. ...

In RF-transmitted composite video, subcarriers remain in the baseband signal after main carrier demodulation to be separated in the receiver. The audio component of the transmitted signal is in a separate carrier and not integral to the video component. In wired video connections, component video retains the integrated subcarrier signal structure found in the transmitted baseband signal, while S-Video places the chrominance and luminance subcarriers on separate wires to eliminate subcarrier crosstalk and enhance the signal bandwidth and strength (picture sharpness and brightness). Composite video, also called CVBS (Composite Video Blanking and Sync), is the format of an analog television (picture only) signal before it is combined with a sound signal and modulated onto an RF carrier. ... Demodulation is the act of removing the modulation from an analog signal. ... Three cables, each with RCA plugs at both ends, are often used to carry analog component video Component video is a video signal that has been split into two or more components. ... S-Video (also known as Y/C) is a baseband analog video format offering a higher quality signal than composite video, but a lower quality than RGB and component video. ... This article refers to the English port of Sharpness. ...

Private audio

Before satellite, Muzak was transmitted to department stores on FM subcarriers. The United States Federal Communications Commission (FCC) also allowed betting parlors in New York state to get horse racing results from the state gaming commission via the same technology. U.S. military MILSTAR communications satellite A communications satellite (sometimes abbreviated to comsat) is an artificial satellite stationed in space for the purposes of telecommunications. ... Muzak Holdings LLC is a company, founded in 1934, that is best known for distribution of music to retail stores and other companies. ... The interior of a typical Macys department store. ... FCC redirects here. ... This article is about the state. ... Horse-racing is an equestrian sporting activity which has been practiced over the centuries; the chariot races of Roman times were an early example, as was the contest of the steeds of the god Odin and the giant Hrungnir in Norse mythology. ...

Many non-commercial educational FM stations in the US (especially public radio stations affiliated with NPR) broadcast a radio reading service for the blind, which reads articles in local newspapers and sometimes magazines. The vision-impaired can request a special radio, permanently tuned to hear audio on a particular subcarrier frequency (usually 67 kHz or 92 kHz), from a particular FM station. The term non-commercial educational (NCE) applies to a radio station that does not accept or air advertisements, as defined in the U.S. by the FCC. NCE stations do not pay licensing fees for their non-profit use of the radio spectrum. ... Public broadcasting (also known as public service broadcasting or PSB) is the dominant form of broadcasting around the world, where radio, television, and potentially other electronic media outlets receive funding from the public. ... NPR logo For other meanings of NPR see NPR (disambiguation) National Public Radio (NPR) is a private, not-for-profit corporation that sells programming to member radio stations; together they are a loosely organized public radio network in the United States. ... A radio reading service or reading service for the blind is a service of many public radio stations, where a narrator reads newspapers and magazines aloud for the benefit of the blind and vision-impaired. ...

Services like these and others on broadcast FM subcarriers are referred to as a Subsidiary Communications Authority (SCA) service by the FCC in the United States, and as Subsidiary Communications Multiplex Operations (SCMO) by the Canadian Radio-television and Telecommunications Commission (CRTC) in Canada. The Canadian Radio-television and Telecommunications Commission (CRTC, in French Conseil de la radiodiffusion et des télécommunications canadiennes) was established in 1968 by the Canadian Parliament to replace the Board of Broadcast Governors. ...

Datacasting

The RDS/RBDS subcarrier (57 kHz) allows FM radios to display what station they are on, pick another frequency on the same network or with the same format, scroll brief messages like station slogans, news, weather, or traffic -- even activate pagers or remote billboards. It can also broadcast EAS messages, and has a station "format" name ALERT to automatically trigger radios to tune in for emergency info, even if a CD is playing. While it never really caught on in North America, European stations rely on it quite a bit. An upgraded version is built into digital radio. Radio Data System, or RDS, is a standard from the European Broadcasting Union for sending small amounts of digital information using conventional FM radio broadcasts. ... Radio Data System, or RDS, is a standard for sending small amounts of digital information using conventional FM radio broadcasts. ... The Emergency Alert System (EAS) is a national system in the U.S. put into place in 1994, superseding the Emergency Broadcast System (EBS) and is jointly coordinated by the Federal Communications Commission (FCC), Federal Emergency Managemant Agency (FEMA), and the National Weather Service (NWS). ... A radio format or programming format describes the overall content broadcast on a radio station. ... CD may stand for: Compact Disc Canadian Forces Decoration Cash Dispenser (at least used in Japan) CD LPMud Driver Centrum-Demokraterne (Centre Democrats of Denmark) Certificate of Deposit České Dráhy (Czech Railways) Chad (NATO country code) Chalmers Datorförening (computer club of the Chalmers University of Technology) a 1960s... North America North America is a continent[1] in the Earths northern hemisphere and (chiefly) western hemisphere. ... For other uses, see Europe (disambiguation). ... This article needs to be cleaned up to conform to a higher standard of quality. ...

MSN Direct uses subcarriers to transmit traffic, gas prices, movie times, weather and other information to GPS navigation devices, wristwatches, and other devices. Many of the subcarriers are from stations owned by Clear Channel. The technology is known as DirectBand. MSN Direct is an FM radio-based digital service which allows portable devices to receive information from MSN services. ... For the geological process, see Weathering or Erosion. ... Over fifty GPS satellites such as this NAVSTAR have been launched since 1978. ... This page is about timekeeping devices. ... A clear channel, in the general sense, is a communications channel (such as a radio frequency) on which only one transmitter operates at a time. ... DirectBandâ„¢ is a North American wireless datacast network owned and operated by Microsoft. ...

FMeXtra on FM uses dozens of small COFDM subcarriers to transmit digital radio in a fully in-band on-channel manner. Removing other analog subcarriers (such as stereo) increases the audio quality or channels available, and other non-audio metadata that can be sent along with it such as album covers, song lyrics, artist info, concert data, and more. FMeXtra is an in-band on-channel digital radio broadcasting technology created by Digital Radio Express. ... Orthogonal frequency division modulation (OFDM, also called orthogonal frequency division multiplexing) is a technique for the modulation of digital information onto an analog carrier electromagnetic (e. ... In-band on-channel (IBOC) is a method of transmitting digital radio and analog radio broadcast signals simultaneously on the same frequency. ... Metadata is data about data. ...

Telemetry and foldback

Many stations use subcarriers for internal purposes, such as getting telemetry back from a remote transmitter, often located in a difficult-to-access area at the top of a mountain. A station's engineer can carry a decoder around with him and know anything that's wrong, as long as the station is on the air and he is within range. This is the essence of a wireless transmitter/studio link. Telemetry is a technology that allows the remote measurement and reporting of information of interest to the system designer or operator. ... Antenna tower of Crystal Palace transmitter, London A transmitter is an electronic device which, usually with the aid of an antenna, propagates an electromagnetic signal such as radio, television, or other telecommunications. ... For the use of the term in networking, see Wireless networking. ... This article does not cite any references or sources. ...

On wireless studio/transmitter links (STLs), not only are the broadcast station's subcarriers transmitted, but other remote control commands as well. Thus, the STL's total bandwidth may actually be even wider than the station's. This is also used sometimes when transmitting more than one station at a time. A studio-transmitter link (or STL) sends a radio stations or television stations audio and video from the broadcast studio to a transmitter in another location. ... For other uses, see Remote control (disambiguation). ... Command has multiple meanings: An order. ...

Interruptible foldback, such as for remote broadcasting, is also possible over subcarriers, though its role is limited. IFB (interruptible foldback often misidentified as interruptible Feedback) systems are used in broadcast and motion picture production for crew communication, audio monitoring and cueing. ...

MCPC satellites

Analog satellite television and terrestrial analog microwave relay communications rely on subcarriers transmitted with the video carrier on a satellite transponder or microwave channel for the audio channels of a video feed. There are usually at frequencies of 5.8, 6.2, or 6.8 MHz (the video carrier usually resides below 5 MHz on a satellite transponder or microwave relay). Extra subcarriers are sometimes transmitted at around 7 or 8 MHz for extra audio (such as radio stations) or low-to-medium speed data. This is referred to as multiple channel per carrier (MCPC). Analog television (or analogue television) encodes television and transports the picture and sound information as an analog signal, that is, by varying the amplitude and/or frequencies of the broadcast signal. ... Satellite television is television delivered by way of communications satellites, as compared to conventional terrestrial television and cable television. ... This article is about the type of Electromagnetic radiation. ... Automotive style miniature relay A relay is an electrical switch that opens and closes under the control of another electrical circuit. ... An Ontario Highway 407 toll transponder In telecommunication, the term transponder (short-for Transmitter-responder and sometimes abbreviated to XPDR, XPNDR or TPDR) has the following meanings: An automatic device that receives, amplifies, and retransmits a signal on a different frequency (see also broadcast translator). ... In electronics, telecommunications and computer networks, multiplexing (short muxing) is a term used to refer to a process where multiple analog message signals or digital data streams are combined into one signal. ...

This is now mostly superseded by digital TV (usually DVB-S2 or another MPEG-2-based system), where audio and video data are packaged together in a single transport stream. Digital television (DTV) uses digital modulation and compression to broadcast video, audio and data signals to television sets. ... DVB-S2 is a newer specification of the DVB-S (Digital Video Broadcasting) standard. ... MPEG-2 is a standard for the generic coding of moving pictures and associated audio information [1]. It is widely used around the world to specify the format of the digital television signals that are broadcast by terrestrial (over-the-air), cable, and direct broadcast satellite TV systems. ... Streaming media are media that are consumed (read, heard, viewed) while it is being delivered. ...

See also

• Subsidiary Communications Authority (SCA)