i don't know about the unit but this is the way i see it. when you speak to someone who is deaf, you speak in sign language and if you don't know it you can move your lips slowly so they can read it and understand what you're saying. or you can type it on the phone and whatever device. when you speak to blind people, you speak nicely and the way you normally speak because nothing is wrong just treat them the same!! when you speak to someone with another native tongue, talk respectfully because they might not know what you're saying since they have a different language than you.
hope this helps, God bless!
