Behind bars? Apple issues apology for overstating iPhone signal strength

Apple Inc.

has issued an apology to iPhone 4 consumers for a software glitch that overstates phone signal strength -- an error the technology giant says has been there since the first iPhone.

In an open letter to iPhone 4 consumers, Apple says it was "stunned to find that the formula we use to calculate how many bars of signal strength to display is totally wrong." That formula displays two more bars than it should.

The iPhone 4 reception issue is compounded when users grip the phone in a way that covers the black strip in the lower left corner of the metal band. Some consumers complained to Apple that their iPhone 4s can drop as much as four or five signal strength bars when the phone is held that way. The company says those complaints led it to find the software formula error.