thumb|right|200px|The RDS Logo Radio Data System, or RDS, is a communications protocol standard for embedding small amounts of digital information in conventional FM radio broadcasts. The RDS system standardises several types of information transmitted, including time, station identification and programme information.
Both use a 57kHz subcarrier to carry data at 1187.5 bits per second. The 57kHz frequency was chosen for being the third harmonic of the pilot tone for FM stereo, so it would not cause interference or intermodulation with it, or with the stereo difference signal at 38 kHz (the second harmonic). The data format utilises error correction. RDS defines many features including how private (in-house) or other undefined features can be "packaged" in unused program groups.
RDS was inspired by the development of the Autofahrer-Rundfunk-Informationssystem (ARI) in Germany by the Institut für Rundfunktechnik (IRT) and the radio manufacturer Blaupunkt. ARI used a 57kHz subcarrier to indicate the presence of traffic information in an FM radio broadcast.
The EBU Technical Committee launched a project at its 1974 Paris meeting to develop a technology with similar purposes to ARI, but which was more flexible and which would enable automated retuning of a receiver where a broadcast network transmitted the same radio programme on a number of different frequencies. The modulation system was based on that used in a Swedish paging system and the baseband coding was a new design, mainly developed by the British Broadcasting Corporation (BBC) and the IRT. The EBU issued the first RDS specification in 1984.
Enhancements to the alternative frequencies functionality were added to the standard and it was subsequently published as a European Committee for Electrotechnical Standardization (CENELEC) standard in 1990.
In 1992 the US National Radio Systems Committee issued the North American version of the RDS standard, called there Radio Broadcast Data System. The CENELEC standard was updated in 1992 with the addition of Traffic Message Channel and in 1998 with Open Data Applications and, in 1999, it was published worldwide as IEC standard 62106.
Content and implementation
The following information fields are normally contained in the RDS data:
- Alternative Frequencies This allows a receiver to re-tune to a different frequency providing the same station when the first signal becomes too weak (e.g. when moving out of range). This is often utilised in car stereo systems.
- Clock Time Can synchronize a clock in the receiver or the main clock in a car. Due to transmission vagaries, CT can only be accurate to within 100 ms of UTC.
- Enhanced Other Networks Allows the receiver to monitor other networks or stations for traffic programmes, and automatically temporarily tune into that station.
- Programme Identification This is the unique code that identifies the station. Every station receives a specific code with a country prefix. In the US, PI is determined by applying a formula to the station's call sign.
- Programme Service This is simply an eight-character static display that represents the call letters or station identity name. Most RDS capable receivers display this information and, if the station is stored in the receiver's presets, will cache this information with the frequency and other details associated with that preset.
- Programme Type This coding of up to 31 pre-defined programme types – e.g. (in Europe): PTY1 News, PTY6 Drama, PTY11 Rock music, – allows users to find similar programming by genre. PTY31 seems to be reserved for emergency announcements in the event of natural disasters or other major calamities.
- Regional This is mainly used in countries where national broadcasters run "region-specific" programming such as regional opt-outs on some of their transmitters. This functionality allows the user to "lock-down" the set to their current region or let the radio tune into other region-specific programming as they move into the other region.
- Radio Text This function allows a radio station to transmit a 64-character free-form textual information that can be either static e.g. station slogans or in sync with the programming such as the title and artist of the currently-playing song.
- TA, TP
- Traffic Announcement, Traffic Programme The receiver can often be set to pay special attention to this flag and e.g. stop the tape/pause the CD or retune to receive a Traffic bulletin. The TP flag is used to allow the user to find only those stations that regularly broadcast traffic bulletins whereas the TA flag is used to stop the tape or raise the volume during a traffic bulletin.
- Traffic Message Channel Digitally encoded traffic information. Not all RDS equipments supports this. Often available for Automotive navigation systems. In many countries only encrypted data is broadcast, and so a subscription and appropriate decoder is required to use.
As far as implementation is concerned, most car stereos will support at least AF, EON, REG, PS and TA / TP.
- More expensive car stereos will offer TMC, RT and / or PTY, perhaps with "NEWS" override.
- Home systems, especially hi-fi receivers, will mainly support functions like PS, RT and PTY.
There are a growing number of RDS implementations in portable and navigation devices thanks to lower priced, small footprint solutions. The Apple iPod's Radio Remote accessory is one such device. Others include Griffin Technology's iTrip AutoPilot, Navigon 5100, Magellan Maestro 4250, Microsoft Zune, Insignia NS-8V24, NS-4V24, NS-2V17, Garmin Nuvi360, Sony Ericsson K600i, K550i, K750i, K770i, K790i, K800i, K810i,K850i, W200i, W300i, W380i , W580i, W600i, W610i, W660i, W810i, W830i, P990i, P1i, W850i, W890i, W910i, W950i, W700i, and Z550i, Motorola L9, E6, E2, Motorola VE66, W375,W396,W230,W270, L6i and W220, Nokia 3600 slide, 5220 XpressMusic, 5310, 5320 XpressMusic, 5610, 5800 XpressMusic, 6220 Classic, 6300i, 6500 slide, 7210 Supernova, 7310 Supernova, 7510 Supernova, 7610 Supernova, N78, N96 and N97, LG Viewty, LG KS-20, LG KP500 Cookie, O2 ATOM LIFE,Samsung SGH-F330, SGH-G800, SGH-L170, SGH-E950, SGH-U600 and SGH-U900.
The following table lists the RDS and RBDS Program Type codes and their meanings:
PTY code RDS Program type (EU) RBDS Program type (North America) 0 No programme type or undefined No program type or undefined 1 News News 2 Current affairs Information 3 Information Sports 4 Sport Talk 5 Education Rock 6 Drama Classic Rock 7 Culture Adult Hits 8 Science Soft Rock 9 Varied Top 40 10 Pop Music Country 11 Rock Music Oldies 12 Easy Listening Soft 13 Light classical Nostalgia 14 Serious classical Jazz 15 Other Music Classical 16 Weather Rhythm and Blues 17 Finance Soft Rhythm and Blues 18 Children’s programmes Language 19 Social Affairs Religious Music 20 Religion Religious Talk 21 Phone In Personality 22 Travel Public 23 Leisure College 24 Jazz Music Unassigned 25 Country Music Unassigned 26 National Music Unassigned 27 Oldies Music Unassigned 28 Folk Music Unassigned 29 Documentary Weather 30 Alarm Test Emergency Test 31 Alarm Emergency
Example RDS Usage
The following three images illustrate how RDS can be used on an FM radio station; the latter two were taken when the radio was tuned to Nottingham radio station 96 Trent FM. All the images are of the display on the Sony XDR-S1 DAB/FM/MW/LW portable radio.
Scrolling PS messages are illegal in the U.K. because of the potential of distracting drivers on the road. Scrolling messages are, however, widely used by pirate radio stations and are common in the U.S.
FM subcarrier usage
In addition, RDS is being proposed as the data transmission protocol in California's pioneering "Programmable Communicating Thermostat" (PCT) program. The proposed technology would allow electricity consumers exposed to “time-based pricing” for electricity to respond to an RDS signal containing price information when their retail electricity price changed during periods of high wholesale electricity costs or abnormally high demand that threatened the stability of the electricity grid. The PCT could then automate any actions that the consumer had pre-programmed the device to take. For example, if the price of electricity went up on a hot afternoon because of extremely high demand, the consumer could preset the PCT to increase their air conditioner cooling set point by a few degrees in order to reduce their overall electricity consumption and bill. The technology could be extended to other home electricity consuming devices such as hot water heaters, clothes dryers, dishwashers, pool pumps, etc. allowing consumers under time-based pricing for electricity significant automatic control over their electricity consumption during periods when the price of electricity is naturally higher than normal. The goal is to give consumers a choice between paying more for high value peak electricity, or reducing their lowest value loads at those times. Such voluntary “demand response” behavior could significantly reduce the price of electricity during non-peak periods because of reduced need for infrequently used peaking power plants, and also reduce the chances of black-outs during emergency events when the electricity grid is stressed or damaged.
RDS sub carrier use for the control of peak power has been in development in Australia since early 2000. ETSA the South Australia Electricity Trust and Saab Systems Australia a local South Australian company pioneered the idea after Trent Ryan a Saab engineer developed the idea in late 1999 and brought it to Saab for further refinement.
Companies such as Silicon Labs in Austin, Texas and NXP Semiconductors (formerly Philips) offer single chip solutions that are found in these devices. The Silicon Labs part supports PS, RT, PTY, TMC, and all other RDS types in a single 3x3 chip and its intended purpose is portable usage (such as mobile phones and MP3 players). NXP also has solutions in this field, and has some automotive chips.
High-level RDS APIs
- Advanced Multimedia Supplements (JSR-234) (in Java programming language)
- OpenMAX AL (in C programming language)
- "March 2009: RDS is now 25 – the complete history" (PDF). Geneva, Switzerland: The RDS Forum. 2009-03-27. p. 1. Retrieved 2009-05-17.
- The Directory of European FM Broadcasting, European FM Handbook 2002-2003, 13th edition, published July 1st 2002, B5 format, ISBN 951-98733-1-7 
- Dietmar Kopitz, Bev Marks, RDS: Radio Data System (Mobile Communications Library), ISBN 0-89006-744-9 
- United States RBDS Standard - Specification of the radio broadcast data system (RBDS)
- The RDS Forum is the professional association of the users of the Radio Data System broadcast technology
- BBC factsheet - Radio Data System (RDS) in HTML format
- radiovalladolid.com -- Gran información en R.D.S. (Español)