how to recognize the backspace character?

["Kader Diagne" <kader@cs.uni-sb.de>]

I am trying to read a backspace character using read-char but it doesn't work.

The situation:

         ? (read-char) 
           a             ;; was given: a
           #\a

         ? (read-char)
                         ;; was given : hit the space bar
          #\Space

The problem:
      
         ? (read-char)
                         ;; was given : hit the backspace 
 The reader still wait for an input and ignores the backspace.
May anybody tell me what's wrong ?

Thanks in advance.
AKD.