Radio Data System

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The RDS Logo

Radio Data System, or RDS, is a 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 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 programme 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 57kHz 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 38kHz (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 programme groups.

1 Content and implementation
2 RDS support
3 RDS chipsets
4 Program Types
5 Example RDS Usage
6 FM subcarrier usage
7 See also
8 External links

[edit] Content and implementation

The following information fields are normally contained in the RDS data:

AF: Alternate 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 vagulearities, CT can only be accurate to within 100ms of UTC.
EON: Enhanced Other Networks. Allows the receiver to monitor other stations for traffic broadcasts.
PI: Program Identification. This is the unique code that identifies the station. Every station receives a specific code with a country prefix.
PS: Program 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: Program 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 links. 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: Travel Announcements, Traffic Program. The receiver can often be set to pay special attention to this flag and e.g stop the tape 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. Requires a RDS-TMC decoder.

[edit] RDS support

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 Microsoft Zune, Garmin Nuvi360, Sony-Ericsson K750i, K800i, W600i, W830i and W850i.

[edit] RDS chipsets

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.

[edit] Program Types

The following table lists the RDS and RBDS Program Type codes and their meanings:

PTY code	RDS Program type (EU)	RBDS Program type (USA)
0	No program 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	M.O.R. Music	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

[edit] 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.

Typical radio display when no RDS data is available

Typical radio display showing the PS name (programme service) field.

Sample Radio Text usage, in this case showing the name and artist of the song being broadcast - Duran Duran's Save a Prayer - the bottom line scrolls to reveal the rest of the text.