When scanning it seems that the machine requires you to press the button on the adjacent alphanumeric pad in the very bottom right corner - has a symbol(s) on it that look like a comma, an up arrow and 2 dots - each above a rectangle. what is this button? Why must I press it to complete my scan? The manual is lost - this is the copier/printer/scanner at my workplace. Any help would be greatly appreciated. Many thanks.