These are instructions on how to replace the signal strength bars on your iPhone with a numerical representation of reception strength. (ie. numbers instead of bars).
Result:
HOW TO REPLACE YOUR iPHONE SIGNAL STRENGTH BARS IN DECIBEL
Step One
Press to launch MobilePhone from your Springboard.
Step Two
Tap the keyboard tab then dial *3001#12345#*.
Step Three
Your iPhone will now launch Field Test. Notice your strength bars have been replaced with a number. This number is your reception strength measured in decibels. The closer to 0dB the stronger your signal.
Step Four
Press and hold the Power button until the power slider appears.
Step Five
Press and hold the
Home button until the Field Test program is terminated. Notice the signal strength numbers still remain.
If you want Switch Back to Bars
Step One
Dial *3001#12345#* again to enter Field Test mode.
Step Two
Press the signal strength at the top left of screen to toggle between numbers and bars.
Step Three
Then press the Home button to exit Field Test mode.