A radio button user interface element, used in form fields with two or more choices. Differs from a checkbox, in that only one response can be selected.
This emoji generally shows the on/enabled state for the radio button, with a smaller circle inside a larger outer circle.
Radio Button was approved as part of Unicode 6.0 in 2010 and added to Emoji 1.0 in 2015.
U+1F518
? Radio button