Radio Data System, or RDS, is a communications protocol standard from the European Broadcasting Union for sending small amounts of digital information using conventional FM radio broadcasts. The RDS system standardises several types of information transmitted, including time, track/artist info and station identification. RDS has been standard in Europe and Latin America since the early 1990s, but less so in North America.
Radio Broadcast Data System is the official name used for the U.S. version of RDS, though the "RDS" name seems to be at least as common in usage. The two standards are nearly identical, with only slight differences, mainly in which numbers are assigned to each of 31 musical and other program formats the RBDS system can identify. RBDS was approved by the NRSC, RDS by the EBU.
Both use a 57kHz subcarrier to carry data at 1187.5 bits per second. The 57 kHz was chosen for being the third harmonic (3×) 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 (2×). The data format utilises error correction. RDS defines many features (see below), including how private (in-house) or other undefined features (such as differential GPS) can be "packaged" in unused program groups.
Content and implementation
The following information fields are normally contained in the RDS data:AF: 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.CT: Clock Time
Can synchronise 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
.EON: Enhanced Other Networks
Allows the receiver to monitor other networks or stations for traffic programmes
, and automatically temporarily tune into that station.PI: 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
.PS: 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.PTY: 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.REG: 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.RT: 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.TMC: 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, K790i, K800i, K810i, W200i, W300i, W380i , W580i, W600i, W610i, W660i, W810i, W830i, P990i, W850i, W890i, W950i, W700i, and Z550i, Motorola L9, E6, E2, W375,W396,W230,W270, L6i and W220, Nokia 3600 slide, 5220 XpressMusic, 5310, 5320 XpressMusic, 5610, 6220 Classic, 6300i, 6500 slide, 7210 Supernova, 7310 Supernova, 7510 Supernova, 7610 Supernova, N78 and N96, LG Viewty, LG KS-20, 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:
|| RDS Programme type (EU)
|| RBDS Program type (USA) |
|| No programme type or undefined
|| No program type or undefined |
|| News |
|| Current affairs
|| Information |
|| Sports |
|| Talk |
|| Rock |
|| Classic Rock |
|| Adult Hits |
|| Soft Rock |
|| Top 40 |
|| Pop Music
|| Country |
|| Rock Music
|| Oldies |
|| M.O.R. Music
|| Soft |
|| Light classical
|| Nostalgia |
|| Serious classical
|| Jazz |
|| Other Music
|| Classical |
|| Rhythm and Blues |
|| Soft Rhythm and Blues |
|| Children’s programmes
|| Language |
|| Social Affairs
|| Religious Music |
|| Religious Talk |
|| Phone In
|| Personality |
|| Public |
|| College |
|| Jazz Music
|| Unassigned |
|| Country Music
|| Unassigned |
|| National Music
|| Unassigned |
|| Oldies Music
|| Unassigned |
|| Folk Music
|| Unassigned |
|| Weather |
|| Alarm Test
|| Emergency Test |
|| 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.
It should be noted that the use of scrolling PS is not recommended, given the potential of distracting drivers on the road. This has, however, become common in the US.
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.
- 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
High-level RDS APIs