Subsidiary Communications Authorization (SCA) in the United States, and Subsidiary Communications Multiplex Operation (SCMO) in Canada, is a subcarrier on a radio station, allowing the station to broadcast additional services as part of its signal.
"Subsidiary Communications Authorization" is the United States Federal Communications Commission's official designation for this type of service. SCA was deregulated in 1983; since then, both AM and FM licensed broadcast stations have been allowed to use subcarriers in the United States in general without requiring separate authority; authorization is only required for some uses which are still otherwise regulated, such as common carrier or Land Mobile Radio Service transmissions.[1] The fidelity (bandwidth) of SCA channels on FM is generally quite limited compared to that of the main program material, resulting in audio quality similar to AM radio broadcasting. By extension, the already limited bandwidth of AM means that it is impossible to multiplex any secondary audio service on an AM signal; any SCA usage would be limited to text.
The Canadian Radio-television and Telecommunications Commission (CRTC) calls this service "Subsidiary Communications Multiplex Operation" (SCMO). SCMO for internal uses by the radio station, such as internal monitoring and cue control, are allowed under the normal broadcasting certificate. Non-broadcasting uses are allowed when the type of use is authorized[clarification needed] under other radio and telecommunications acts, and may require a fee.[2]
In Australia, the service is called "Ancillary Communications Service" (ACS) and the Radio Data System is specifically addressed by government guidelines.[3]
Subcarrier channels falling under the description of SCA are usually on FM at 67 kHz and 92 kHz from the main carrier, and 67 kHz is the most common. Major uses of SCA include:
As a transmitter/studio link, sending telemetry data from a broadcast FM station's transmitter to the studio for monitoring the condition of the transmitter
For commercial paging service: sent via FM subcarrier to the subscriber with a compatible pager
For data broadcasting: Microsoft's now-defunct DirectBand service (used by MSN Direct) relied on SCA FM subcarriers; Data Broadcasting Corporation's Signal service used SCA for sending real-time stock quotes.
For closed-circuit or specialized radio programming aimed at certain markets or professions, such as the Physician's Radio Network, agricultural commodity & futures information (via voice or data), or ethnic foreign-language radio programming.
For the transmission of Muzak's background music service to its subscribers (i.e., supermarkets, restaurants, etc.), this transmission method (along with another method using leased phone lines) have been phased out with Muzak now transmitting its programming via satellite.
Most programming transmitted by SCA/SCMO is usually pay/subscription-based, making unauthorized reception of such programming illegal, but programming which is not commercial in nature, such as reading services, can be received legally.[citation needed]
Companies in the past such as Norver, ComPol, Mani National Corporation, McMartin, & Dayton Industrial; and current companies such as Metrosonix make radios and adapters for receiving SCA/SCMO channels. It can be difficult to keep the main channel's FM stereo difference subcarrier from interfering with such SCA decoders, as the stereo signal is a much stronger signal, and distortions due to multipath can also cause problems.[citation needed]
See also
Bruce Elving, author and advocate of SCA broadcasting
Radio Data System — widespread program information standard; sometimes considered a type of SCA
^"SP-1452 — Spectrum Policy Provisions to Permit the Use of Digital Radio Broadcasting Installations to Provide Non-Broadcasting Services". Industry Canada, Spectrum Management and Telecom. September 1997. Retrieved 2009-03-28.
^"Appendix 2: Emission Standard for the Australian Frequency Modulation Sound Broadcasting Service" (PDF). Broadcasting Services (Technical Planning) Guidelines 2007. Australian Communications and Media Authority. 2007-07-06. Retrieved 2022-12-01.
^"Where to find VoicePrint". Toronto: National Broadcast Reading Service. Retrieved 2022-12-01.
^"Time Running Out for FM6 Stations?" by Randy J. Stine, May 31, 2021 (radioworld.com)
External links
The FCC's page for SCA
1983 rules on subcarriers
August 23, 2023
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This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Subsidiary communications authority news newspapers books scholar JSTOR March 2009 Learn how and when to remove this template message Subsidiary Communications Authorization SCA in the United States and Subsidiary Communications Multiplex Operation SCMO in Canada is a subcarrier on a radio station allowing the station to broadcast additional services as part of its signal Contents 1 Background 2 Receiving the SCA Signal 3 See also 4 References 5 External linksBackground Edit Subsidiary Communications Authorization is the United States Federal Communications Commission s official designation for this type of service SCA was deregulated in 1983 since then both AM and FM licensed broadcast stations have been allowed to use subcarriers in the United States in general without requiring separate authority authorization is only required for some uses which are still otherwise regulated such as common carrier or Land Mobile Radio Service transmissions 1 The fidelity bandwidth of SCA channels on FM is generally quite limited compared to that of the main program material resulting in audio quality similar to AM radio broadcasting By extension the already limited bandwidth of AM means that it is impossible to multiplex any secondary audio service on an AM signal any SCA usage would be limited to text The Canadian Radio television and Telecommunications Commission CRTC calls this service Subsidiary Communications Multiplex Operation SCMO SCMO for internal uses by the radio station such as internal monitoring and cue control are allowed under the normal broadcasting certificate Non broadcasting uses are allowed when the type of use is authorized clarification needed under other radio and telecommunications acts and may require a fee 2 In Australia the service is called Ancillary Communications Service ACS and the Radio Data System is specifically addressed by government guidelines 3 Subcarrier channels falling under the description of SCA are usually on FM at 67 kHz and 92 kHz from the main carrier and 67 kHz is the most common Major uses of SCA include For talking book radio reading service for the blind 1 usually carried on NPR affiliated public radio stations in the United States citation needed In Canada this is usually provided by AMI audio over television second audio programs instead 4 As a transmitter studio link sending telemetry data from a broadcast FM station s transmitter to the studio for monitoring the condition of the transmitter For commercial paging service sent via FM subcarrier to the subscriber with a compatible pager For data broadcasting Microsoft s now defunct DirectBand service used by MSN Direct relied on SCA FM subcarriers Data Broadcasting Corporation s Signal service used SCA for sending real time stock quotes For closed circuit or specialized radio programming aimed at certain markets or professions such as the Physician s Radio Network agricultural commodity amp futures information via voice or data or ethnic foreign language radio programming For the transmission of Muzak s background music service to its subscribers i e supermarkets restaurants etc this transmission method along with another method using leased phone lines have been phased out with Muzak now transmitting its programming via satellite Venture Technologies which owns a large number of analog low power television stations with audio subcarriers that operate as FM radio stations proposed using SCA rules to continue transmitting those analog audio services along an ATSC 3 0 signal 5 Receiving the SCA Signal EditMost programming transmitted by SCA SCMO is usually pay subscription based making unauthorized reception of such programming illegal but programming which is not commercial in nature such as reading services can be received legally citation needed Companies in the past such as Norver ComPol Mani National Corporation McMartin amp Dayton Industrial and current companies such as Metrosonix make radios and adapters for receiving SCA SCMO channels It can be difficult to keep the main channel s FM stereo difference subcarrier from interfering with such SCA decoders as the stereo signal is a much stronger signal and distortions due to multipath can also cause problems citation needed See also EditBruce Elving author and advocate of SCA broadcasting Radio Data System widespread program information standard sometimes considered a type of SCA Second audio program SAP a similar service on television signals FMeXtra a digital audio implementation of SCAReferences Edit a b Radio Subcarriers SCAs Subsidiary Communications Authority Federal Communications Commission Audio Division Retrieved 2022 12 01 SP 1452 Spectrum Policy Provisions to Permit the Use of Digital Radio Broadcasting Installations to Provide Non Broadcasting Services Industry Canada Spectrum Management and Telecom September 1997 Retrieved 2009 03 28 Appendix 2 Emission Standard for the Australian Frequency Modulation Sound Broadcasting Service PDF Broadcasting Services Technical Planning Guidelines 2007 Australian Communications and Media Authority 2007 07 06 Retrieved 2022 12 01 Where to find VoicePrint Toronto National Broadcast Reading Service Retrieved 2022 12 01 Time Running Out for FM6 Stations by Randy J Stine May 31 2021 radioworld com External links EditThe FCC s page for SCA A page on SCA and Radio Reading Service history 1983 rules on subcarriers Retrieved from https en wikipedia org w index php title Subsidiary communications authority amp oldid 1147782842, wikipedia, wiki, book, books, library,
