What's the function of ARI button in Blaupunkt Mannheim 27 car radio?

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When ARI button is engaged and there is a traffic info being broadcast, radio plays that info. The sound level for ARI is independent of the radio volume (on my Mannheim it was adjusted with a screw on the back, you needed a screwdriver to do it) so you do not have to listen to radio station and you will still receive traffic news. That means, radio had to be on and tuned to the station but volume knob could be turned to silence. ARI/traffic info would still come out at the preset level. I hope it helps as I believe I remember it qute well despite not seeing my radio in 20 years.