21 things you didn´t know your Iphone could do. NR 21

See your iPhone's actual signal strength.

There's a clever trick that shows the actual signal strength on your iPhone rather than just the dots or bars you usually see in the upper left corner of the screen. 

First, you'll need to access a hidden app on your phone called Field Test Mode. To do this, you'll need to open up your Phone app and dial the following number, *3001#12345#* , including the asterisks and hashtag, and tap "Call."

This opens up Field Test Mode, which is mostly filled with menus of cell signal jargon that you don't need to worry about. What you're interested in is the tiny number in the upper left-hand corner of your iPhone, which should have replaced those cell signal dots. 

While that number can vary anywhere from -40 to -130, it will always be negative, and the closer that number is to zero, the better your cell signal. The best signal you can get would be -40, and no signal at all would be -130.