On  the telephone lin level some distinction can be made
              on  the HAYES-2400,  between jack type RJ12/RJ13  (multi
              line  jack) and the RJ11/RJ41S/RJ45S (single line jack).
              The 1200 only supports the RJ11 (single line), RJ12/RJ13
              (multi  line),  which can be set  by  dipswitches.  This
              typically is different per country.  In the USA and some
              other countries, the telephone set remaines connected in
              parallel  to  the  modem.  In other countries  like  the
              Netherlands the telephone set is switched of, as soon as
              the modem goes off-hook.