my 750 does that as well, it beeps 3 times to notify you that the hour is coming to an end, so thats what it means. as for turning it off, look in the instructions for your radio booklet if u have one. however, my cars an '88 (back in the days of car theft) so im not sure if your radio would be considered ''part of the cars computer'' like mine...u can also look in index for time setting