With all the different iPhone symbols and functions, it can be difficult for even the most proficient iPhone user to keep them all straight. There are two main reasons why you might notice a circle on your iPhone screen. In one instance, the circle appears in the status bar. In the other, it will appear somewhere in the middle of your screen.

AssistiveTouch Feature

If there is a large circle enclosed in a grey box that appears as an overlay on your iPhone screen, your phone's AssistiveTouch feature is enabled. This accessibility feature makes it easier for users to navigate the iPhone when they have trouble using their fingers to touch down on the screen. To turn this function on or off, go to the Settings menu, access your phone's general settings and select "Accessibility." On the accessibility menu, you can toggle the AssistiveTouch feature on and off.

Status Bar Indicator

If the circle you notice appears in your iPhone status bar, it is an indication that your phone is out of reach of a 3G, 4G or EDGE network, but is still able to connect to the Internet through your carrier's GPRS or IxRTT network. These networks are used by iPhone carriers to provide Internet access to their customers.