I came across this on Yahoo Tech. Dial *3001#12345#* and press call. This will direct you to field test, where it will now be displayed as a number. To make it permanent, restart by holding the sleep and home button until it turns off. You can switch back and forth by touching the signal. https://www.yahoo.com/tech/how-to-display-your-iphones-signal-strength-in-numbers-76257989351.html Edit: I did this on my 4s and the number seems to be the default. Even if I leave it on the dots, I notice that it has changed back to the number and is unresponsive to changing without resetting the device. I don't know why it's doing this. The process can be reversed by going through the input process and leave it on the graphic for the signal (the dots) in the field test, then exit the field test.