If you have an iPhone, there’s a secret code that you’ll want to know about, especially if your signal is not always 100%!
Everyone recognizes the five dots in the upper-left corner of the screen. The more black dots, the stronger the signal. But you can actually replace those dots with a more precise measurement: a number.
First, open the phone app, enter the secret code *3001#12345#* and press the call button, which will bring you to Field Test mode.
Once in Field Test mode, notice that the five dots in the upper-left corner have been replaced with a negative number.
According to CNET, around -113 decibels is on the low end of the signal bar range and around -50 decibels is on the high end. In other words, your signal is stronger the closer it is to zero.
In this case, -103 is strong enough to make calls, but it’s too weak to stream video.
To prevent your phone from reverting back to the five dots when you exit Field Test mode, there are a few extra steps that you’ll need to complete.
Start by holding the power button until you see “slide to power off” on the screen.Once that happens, you need to hold the home button until the home screen comes back up with the number displayed instead of the dots.
Using this secret iPhone code can come in handy if you have bad reception and want a more accurate way to predict when and where your phone’s service may be impaired.
Don’t like what you see? Dial *3001#12345#* and hit the home button to switch back to the dots.