Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Display with LEDs surrounding the letter field of the spelling device. Figures refer to the respective flickering frequency in Hz. (a) Low frequency stimulation. (b) Medium frequency stimulation. (c) High frequency stimulation. The cursor is positioned over the E.
