I've managed to replace my signal strength bars by a negative number. However, I don't know how to get back to the signal strength bars. After reading an article, "Bugs & Fixes: iPhone 3GS signal strength oddities" in MacWorld I went into Field Test mode on my iPhone. Here is what I did: WARNING: Once you replace your signal strength bars you may not be able to get them back. The "more accurate numerical indicator" is much more accurate but not quite as easy to see. You've been warned. Quoting from the article by Ted Landau of Macworld: "Finally, at least for AT&T phones, you can get a more accurate numerical indicator of the iPhones current signal strength by manually dialing *3001#12345#* followed by a tap of the Call button." I did this from an original 8G iPhone. However when I got my new 3GS 32G iPhone and restored from my Mac the new "more accurate numerical indicator" feature loaded along with my data. If anyone knows how to restore the signal strength bars I would like to know how to do this.