def add_ext( ext)
      raise "Nur #{ext.size} Erweiterungstexte, 4 benötigt" if ext.size != 4
      str =  "%2.2s%-27.27s" % format_ext(ext[0][0], ext[0][1] )
      str +=  "%2.2s%-27.27s" % format_ext( ext[1][0], ext[1][1] )
      str +=  "%2.2s%-27.27s" % format_ext( ext[2][0], ext[2][1] )
      str +=  "%2.2s%-27.27s" % format_ext( ext[3][0], ext[3][1] )
      # devider 12 blanks
      str += ' ' * 12
      unless  str !~ /\S/ # only add if something is in there .. only whitespace => same as str.blank?
        raise "DTAUS: Längenfehler C/3 #{str.size} " if str.size != 128
        dta_string << str
      end
    end
def add_ext( ext)
      raise "Nur #{ext.size} Erweiterungstexte, 4 benötigt" if ext.size != 4
      str =  "%2.2s%-27.27s" % format_ext(ext[0][0], ext[0][1] )
      str +=  "%2.2s%-27.27s" % format_ext( ext[1][0], ext[1][1] )
      str +=  "%2.2s%-27.27s" % format_ext( ext[2][0], ext[2][1] )
      str +=  "%2.2s%-27.27s" % format_ext( ext[3][0], ext[3][1] )
      # devider 12 blanks
      str += ' ' * 12
      unless  str !~ /\S/ # only add if something is in there .. only whitespace => same as str.blank?
        raise "DTAUS: Längenfehler C/3 #{str.size} " if str.size != 128
        dta_string << str
      end
    end
Add a section-C extension, always containing the section type followed by
 4 segments with 27 chars and an ending seperator of 12 blanks
 Only adds the segement if something is in there
 === Parameter
 <Array[Array[String,String]]>:: two dim. ary containing: [extension type(01 02 03),string content]