IN THE 70S , 80S, AND INTO THE 90S WE USED TO PRINT A BUNCH OF STATIONS SENDING FIVE NUMBER GROUPS AS THE MESSAGE TEXT... THE HEADERS WITH NORMAL ZCZC TYPE STUFF CAME THROUGH OK BUT THE TEXT WAS IN GROUPS OF NUMBERS... WHAT KIND OF UNIT WAS USED TO DECIPHER THIS AND WAS IT MECHANICAL OR ELECTRONIC I WONDER???