It's a logo for an LED diode. It is made up of a rectangle with two lines going down vertically to form a base with a half circle on top of the rectangle where the light would be.
This is a LED Diode icon. We've made it in iOS style
, first introduced in iOS version 7 and supported in all later releases up until now (at least iOS 11). This style is based on thin two-pixel lines and is optimized for 50x50 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 13,300 icons, all in the same style and quality.