| Radio Data System |
Article Index for Radio |
Website Links For Radio |
Information AboutRadio Data System |
| CATEGORIES ABOUT RADIO DATA SYSTEM | |
| broadcast engineering | |
| radio technology | |
|
Radio Data System, or '''RDS''', is a Standard from the European Broadcasting Union for sending small amounts of Digital Information using conventional FM Radio Broadcast s. 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 programme formats the '''RBDS''' system can identify. RBDS was approved by the NRSC , RDS by the EBU . Both use a 57 KHz 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. 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 vagaries, CT can only be accurate to within 100ms of UTC. ;EON: Enhanced Other Networks. Allows the receiver to monitor other stations for Traffic Broadcast s. ;PI: Programme Identification. This is the unique code that identifies the station. Every station receives a specific code with a country prefix. ;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 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 Programme. 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. RDS SUPPORT As far as implementation is concerned, most car stereos will support at least AF, EON, REG, PS and TA / TP.
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 K600i , K750i , K790i , K800i , K810i , W200i , W300i , W600i, W810i , W830i , P990i and W850i and W700i , also Motorola L , E6 , E2 , W375, L6i and W220. 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. Nokia 6500 . PROGRAM TYPES The following table lists the RDS and RBDS Program Type codes and their meanings: 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 RDS is not recommended, given the potential of distracting drivers on the road. Some stations choose to flout this recommendation, particularly in the UK. FM SUBCARRIER USAGE RDS's utilization of the FM subcarrier spectrum, 100 khz FM channel allocation assumed. SEE ALSO Related technologies Related topics EXTERNAL LINKS
|
|
|