Like most mobile devices blackberrys show the signal strength as a number of bars. But this doesn't give a very accurate idea of what the real signal strength is since there are only five bars. To get a more accurate idea of the signal strength on your blackberry you can have the strength shown as a decimal number. To do this hold down the ALT key and type the letter NMLL - your signal strength will be converted from bars to a number. To go back to the bars repeat this process and it'll toggle back to how it was.