Second audio program (SAP), also known as secondary audio programming, is an auxiliary audio channel for analog television that can be

broadcast Broadcasting is the distribution (business), distribution of sound, audio or video content to a dispersed audience via any electronic medium (communication), mass communications medium, but typically one using the electromagnetic spectrum (radio ...

or transmitted both over-the-air and by

cable television Cable television is a system of delivering television programming to consumers via radio frequency (RF) signals transmitted through coaxial cables, or in more recent systems, light pulses through fibre-optic cables. This contrasts with bro ...

. Used mostly for audio description or other languages, SAP is part of the multichannel television sound (MTS) standard originally set by the National Television Systems Committee ( NTSC) in 1984 in the United States. The NTSC video format and MTS are also used in

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tota ...

and

Mexico Mexico ( Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guate ...

Usage

SAP is often used to provide audio tracks in languages other than the native language included in the program. In the United States, this is sometimes used for Spanish-language audio (especially during sports telecasts), often leading to the function being referred to facetiously as the "Spanish audio program". Likewise, some Spanish-language programs may, in rare cases, offer English on SAP. Some stations may relay NOAA Weather Radio services, or, particularly in the case of PBS stations, a local

National Public Radio National Public Radio (NPR, stylized in all lowercase) is an American privately and state funded nonprofit media organization headquartered in Washington, D.C., with its NPR West headquarters in Culver City, California. It differs from othe ...

(NPR) sister station, on the audio channel when SAP is not being used. In Canada, parliamentary and public affairs channel CPAC similarly uses SAP to carry both English and French-language audio. SAP is also a means of distribution for audio description of programs for the visually impaired. Under the Twenty-First Century Communications and Video Accessibility Act of 2010, top U.S. television networks and cable networks have been gradually required to broadcast quotas of audio described programming per-quarter, Since May 26, 2015, broadcasters have been required under the Act to provide dictations on SAP of any "emergency information" displayed in a textual format outside of the

Emergency Alert System The Emergency Alert System (EAS) is a national warning system in the United States designed to allow authorized officials to broadcast emergency alerts and warning messages to the public via cable, satellite, or broadcast television, and both ...

and newscasts.

Frequencies

MTS features, including stereo and SAP, travel on

subcarrier A subcarrier is a sideband of a radio frequency carrier wave, which is modulated to send additional information. Examples include the provision of colour in a black and white television system or the provision of stereo in a monophonic radio bro ...

s of the ''

video Video is an Electronics, electronic medium for the recording, copying, playback, broadcasting, and display of moving picture, moving image, visual Media (communication), media. Video was first developed for mechanical television systems, whi ...

'' carrier, much like color for television. It is ''not'' carried on the audio carrier in the manner of stereo sound for an FM radio broadcast, however, as it only has a frequency deviation of ±25 kHz, whereas regular FM broadcasting has a deviation of ±75 kHz. The SAP subcarrier is located at 78.670 kHz, which is five times the 15.734 kHz corresponding to the MTS pilot signal. In turn, the MTS pilot is locked to the horizontal sync

frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from '' angular frequency''. Frequency is measured in hertz (Hz) which is ...

of the video carrier for stability. The SAP channel contains mono audio which has been dbx- encoded for noise reduction, to improve the signal-to-noise ratio. The SAP audio has a bandpass from 60 Hz to 12 kHz, which is less than the "regular" audio channel which runs from 50 Hz to 15 kHz. Though not technically a SAP channel,

television station A television station is a set of equipment managed by a business, organisation or other entity, such as an amateur television (ATV) operator, that transmits video content and audio content via radio waves directly from a transmitter on the ear ...

s can also broadcast a "PRO" (

professional A professional is a member of a profession or any person who works in a specified professional activity. The term also describes the standards of education and training that prepare members of the profession with the particular knowledge and ski ...

) audio subcarrier which is used to communicate with station personnel, particularly those engaged in electronic news gathering. This one-way audio channel allows individuals at the television station to send messages to people located away from the station, and is frequently employed during on-location newscasts as the foldback channel to reporters and cameramen. This channel is located at 6.5 times the pilot (102.271 kHz), and is also part of the MTS standard.

Other media

Second audio programs are also available in other media. On analog television receive-only satellite television systems, audio programs are manually tuned by their subcarrier frequency, commonly around 6 MHz, often as low as 5.8 or as high as 7.2. These travel the same way as the discrete left and right main audio channels, and ATIS

station ID Station identification (ident, network ID or channel ID or bumper) is the practice of radio and television stations and networks identifying themselves on-air, typically by means of a call sign or brand name (sometimes known, particularly in the ...

, which is heard as

Morse code Morse code is a method used in telecommunication to encode text characters as standardized sequences of two different signal durations, called ''dots'' and ''dashes'', or ''dits'' and ''dahs''. Morse code is named after Samuel Morse, one ...

. On FM radio,

radio reading service A radio reading service or reading service for the blind is a public service of many universities, community groups and public radio stations, where a narrator reads books, newspapers and magazines aloud for the benefit of the blind and vision-im ...

s and other audio programs can be heard on subcarriers through subsidiary communications authority; however, these are generally prohibited from public listening without special equipment.

HD Radio HD Radio (HDR) is a trademark for an in-band on-channel (IBOC) digital radio broadcast technology. It generally simulcasts an existing analog radio station in digital format with less noise and with additional text information. HD Radio is used ...

subchannels, somewhat more widely available, operate on a similar premise but generally carry totally unrelated programming to the main feed. On

digital television Digital television (DTV) is the transmission of television 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 advanc ...

systems, selection is done through a menu as with analog television, though some provide easier access rather than having to dig down to find the option. Stations may also choose to transmit audio-only programs by assigning them to separate digital subchannels with an optional screen of title and artist information; however, this prevents the viewer from watching the main video in the case of television stations.

References

{{DEFAULTSORT:Second Audio Program Broadcast engineering Television technology Broadcasting