Let’s say you are in class, or at the movies, and you don’t want your phone to ring. Slip it into the fully shielded slot. In this position, RF signals in or out will be reduced almost to zero, which is enough to stop the phone from ringing in most circumstances unless you have an especially good connection. You can also store chipped cards (like credit cards) in here to prevent unintentional reading.
Over time, the number of cell phone calls per day, the length of each call, and the amount of time people use cell phones have increased. Because of changes in cell phone technology and increases in the number of base stations for transmitting wireless signals, the exposure from cell phone use—power output—has changed, mostly lowered, in many regions of the United States (1).