Symbol 3888 from ISO 7000 - Title/Meaning: Display test, on 
Function/description: To identify the control that switches on the display test function. To indicate that the display test function is active.
Own work using: iso.org/obp/graphics/grs/435204e4-5f9d-4870-83da-08384b7daf4e 200.png
Vectorization:  Mrmw