ttf) is one of such fonts - and Arial is the default font used in the predefined style 'Standard' in newer versions of AutoCAD. But you need to use a 'rich' font containing the requested symbol. Symbols are contained in most fonts and you can access them through Unicode codes.
These texts don't need to be neccessarily only letters and numbers - you can also use symbols.
Besides the standard dashed linetypes and complex linetypes using shapes, AutoCAD allows to create custom linetypes using texts.
