Autofahrer-Rundfunk-Informationssystem

Before the Radio Data System took over, German drivers relied on ARI (Autofahrer-Rundfunk-Informationssystem) to catch traffic updates on the radio. Launched in 1974 by the German Bundespost in cooperation with the ARD and IRT, the system was a joint project between IRT and Blaupunkt. It worked by tweaking a 57 kHz subcarrier—the third harmonic of the FM stereo pilot tone—to signal when a station was broadcasting traffic info. ARI-equipped radios would light up an indicator to show the feature was active, and many models could automatically search for stations carrying the signal.

The system had three main functions. The basic SK signal simply told the radio a station was ARI-capable; a switch marked SDK or VF would mute the audio unless tuned to such a station, or, on digital sets, trigger an automatic seek for another ARI station if the current one was out of range. The DK signal used a 125 Hz amplitude modulation on the 57 kHz subcarrier to indicate a traffic announcement was in progress, giving priority to announcements. Radios with a DK switch would unmute or cut in over a tape or CD at a fixed volume. Users could cancel a specific announcement, though the process was not intuitive, especially on sets with a simple mechanical toggle. Finally, the BK signal used one of six tones (A through F) for crude geocoding. High-end radios could display the current broadcast zone and let drivers limit searches to their zone, a neighboring one, or any zone.

Blaupunkt tried to bring ARI to the U.S. starting in 1982, pitching it to big-city FM broadcasters. They were the only company selling ARI radios there, hoping to stand out, but the system never caught on. Plans to get other manufacturers on board in the U.S. went nowhere, though those same makers did sell ARI sets in Germany. ARI became obsolete with the rise of RDS, and the ARD shut down its ARI signals on March 1, 2005.