RDS, standing for the Radio Data System, arrived in the UK in the early 90s, adding a basic data and text service to FM radio.
This page contains information and useful links relating to RDS.
Most FM radio stations in the UK use RDS. Along with the audio, small amounts of text and data are transmitted with the radio signal, and can be picked up and processed by radios that have an RDS decode built-in. Such radio receivers can display this information. The information commonly transmitted is:
- Station Name. Most commonly, this is an 8-digit radio station name, e.g. “BBC R.4” or “Jazz FM”
- Programme Type (i.e. Pop, Rock, etc). Known as the PTY flag
- Travel Information. A very useful bit of information sent, is something called the ‘TA flag’. Standing for Traffic Announcement, this can be switched on when a radio station starts a travel report, and switched off at the end. The practical upshot of this, is that your RDS radio can switch to a station carrying travel news, or in a car, pause a cassette or a CD, when local travel news is broadcast. For more, see below.
- Radio Text. This information ‘scrolls’ across RDS radio displays, providing information that’s sent from the radio station. In some cases, it’s the general information about the station, in others, information about the show now on, or for computerised stations, the title and artist of the song that’s currently playing. This is not normally fitted to an in-car radio, as it’s seen as a distraction to drivers
- Enhanced Other Networks – Most commonly used by the BBC, the EON flag allows an RDS radio to know about other associated stations, so a radio can know that when listening to a BBC Radio 4 programme, it should keep an ear on the local BBC station, in case there’s some travel news
- Alternative Frequency. The AF flag contains information about a station’s other FM frequencies, so that the radio can switch to a better signal whilst driving.
- Time and Date. The CF flag carries the current date and time, resetting for summertime, etc. Useful in RDS clock radios!
Click on the following link for an MP3 version of the RDS radio promotion transmitted in the UK in the early 1990s: Ford RDS Promotion
RDS Travel News
Apart from the station name, this is probably the most useful and visible part of the RDS system. When a radio station starts a travel report, they instruct their transmitter site to switch on the RDS TA travel flag. Radios with RDS can see this flag, and get the radio to tell the listener that there’s a travel report. A radio can do this by interrupting the tape or CD that’s playing, or by increasing the volume, to get the listener’s attention. This is an incredibly useful service for motorists, and by listening to a local radio station, you can keep up-to-date with local road conditions and travel flashes, without having to listen to the station’s DJs, music and commercials.
If you listen to local radio, you may hear a series of three tones or beeps played before and after travel and traffic reports. Many think that these tones are the RDS flag, but they’re not – although they are associated with RDS. In order for a transmitter to know that Travel is being broadcast, the radio studio has to tell it, by switching on the TA flag. As studios are often some distance from the transmitter, the studio play a recording of three DTMF tones as part of their travel service. A box at the transmitter site listens for those tones, and when it hears them in the programming, it turns on the Travel Flag. This concept was designed in the 90s by the Engineering team at Essex Radio, in Southend-on-Sea, and has since been used at many of the independent local radio stations across the UK.
- RDS Travel jingle – Click this link to download an example of a travel jingle with the three tones embedded. This is an Essex Radio Travel jingle from 1993, in MP3 format.
Handheld RDS radios start from about £40, and many new cars come with an RDS radio as standard. RDS portable radios, such as the Roberts Rd49, pictured here, can be found at John Lewis.
We also want to give a quick mention here to RDS-TMC.
RDS-TMC stands for Radio Data Systems Traffic Message Channel. It’s road traffic information send over FM radio to special in -car receivers. In the UK, RDS-TMC data is collected by the company ITIS, and sent out over-air on Classic FM.
Some new sat nav devices are capable of getting RDS-TMC data, and updating routes to avoid traffic hotspots. The service is compatible with a number of TomTom Sat Nav devices, including: TomTom Go 510, Go 710, Go 720 and 910 units. A special RDS-TMC receiver is required.
RDS-TMC is available in the UK, transmitted by Classic FM. RDS-TMC is also available in the following countries: Austria, Belgium, the Czech Republic, Denmark, Finland, France, Germany, Italy, Netherlands, Spain, Sweden and Switzerland.
- Does DAB support RDS travel news announcements?
– The answer to this one appears to be no. Also travel data over DAB appears to be in the DAB spec, this currently isn’t implemented by any of the UK broadcasters, or over the transmission network. Looks like, at least for the moment, you’ll need to stick with FM radio for RDS TA announcements.
Other questions? – Please ask in our forum.
Useful RDS Links
- The RDS forum – The official source for RDS information
- BBC RDS factsheet – A useful sheet of RDS information from the BBC.
- Travel news on the move – Information on getting real-time travel and traffic information
- Our discussion board – Get talking about all aspects of radio, including RDS and digital
- Griffin Navigate – FM radio with RDS for iPhone
- Join our free Mailing list to be kept up-to-date with site updates.