Tryb offline and other 69,800 icons from Icons8 icon pack follow the visual guidelines of the operating systems: Windows, iOS, Android KitKat, and Material. PNG format is free up to 100x100 px. Icons are availble for download in PNG and vector (SVG, PDF, EPS, and more).
It's an image of a long diagonal line from the top left to the bottom right. It's cutting a signal image in half diagonally. The signal image is a small circle in the middle with two partial curved lines emanating from each side.