Editing Radio Data System (section)

{{Short description|Communications protocol standard in FM radio broadcasts}}
{{Use dmy dates|date=June 2022}}
{{Infobox technology standard
| title             = Radio Data System
| long_name         = 
| image             = Radio Data System.svg
| image_size        = 
| alt               = 
| caption           = The RDS logo
| abbreviation      = 
| native_name       = <!-- Name in local language. If more than one, separate using {{plain list}} -->
| native_name_lang  = <!-- ISO 639-1 code e.g. "fr" for French. If more than one, use {{lang}} inside native_name items instead -->
| status            = Active
| year_started      = {{Start date and age|1984|df=y}}
| first_published   = <!-- {{Start date|YYYY|MM|DD|df=y}} -->
| version           = 
| version_date      = 
| preview           = 
| preview_date      = 
| organization      = 
| committee         = [[International Electrotechnical Commission]]
| series            = 
| editors           = 
| authors           = 
| base_standards    = 
| related_standards = 
| predecessor       = 
| successor         = 
| domain            = 
| license           = 
| copyright         = 
| website           = <!-- {{URL|example.com}} -->
}}

'''Radio Data System''' ('''RDS''') is a [[communications protocol]] standard for embedding small amounts of [[digital information]] in conventional [[FM broadcasting|FM radio broadcast]]s. RDS standardizes several types of information transmitted, including [[time]], [[station identification]] and program information.

The standard began as a project of the [[European Broadcasting Union]] (EBU), but has since become an international standard of the [[International Electrotechnical Commission]] (IEC). '''Radio Broadcast Data System''' ('''RBDS''') is the official name used for the U.S. version of RDS.<ref name=NRSC4B>{{cite web|title=NRSC-4-B United States RBDS Standard|url=http://www.nrscstandards.org/SG/nrsc-4-B.pdf|publisher=National Radio Systems Committee|date=April 2011|access-date=2011-12-31|archive-date=2016-10-20|archive-url=https://web.archive.org/web/20161020015638/http://www.nrscstandards.org/SG/nrsc-4-B.pdf|url-status=dead}}</ref> The two standards are only slightly different, with receivers able to work with either system with only minor inconsistencies in the displayed data.

Both versions carry data at 1,187.5 [[bits per second]] (about 1.2{{nbsp}}[[kbit/s]]) on a 57&nbsp;[[kHz]] [[subcarrier]], so there are exactly 48 cycles of subcarrier during every data bit. The RBDS/RDS subcarrier was set to the third [[harmonic]] of the 19&nbsp;kHz [[FM stereo#Stereo FM|FM stereo]] [[pilot tone]] to minimize [[Interference (communication)|interference]] and [[intermodulation]] between the data signal, the stereo pilot and the 38&nbsp;kHz [[DSB-SC]] stereo difference signal. (The stereo difference signal extends up 38&nbsp;kHz + 15&nbsp;kHz = 53&nbsp;kHz, leaving 4&nbsp;kHz for the lower sideband of the RDS signal.)

The data is sent with an [[error correction code]], but receivers may choose to use it only for [[error detection]] without correction. RDS defines many features including how private (in-house) or other undefined features can be "packaged" in unused program groups.

RDS is only used on analog stations. The [[HD Radio]] equivalent is [[Program-associated data]] (PAD), now called Program service data (PSD).