A refreshable braille display or braille terminal is an electro-mechanical device for displaying characters, usually by means of round-tipped pins raised through holes in a flat surface. Visually impaired computer users who cannot use a standard computer monitor can use it to read text output. Deafblind computer users may also use refreshable braille displays. Speech synthesizers are also commonly used for the same task, and a blind user may switch between the two systems or use both at the same time depending on circumstances.