Again, thanks for replying and for the link.
The info. in the link tells what I already knew. That an Alt chord is a Dominant chord [1,3,5,7b]. And then the alterations occur in the (5th) and the (9th) degrees of the scale.
But it dosn`t explain why the four chords have the same name(ALT).
I guess my question is gonna remain with no answer.