I just discovered that after setting up low tones (1275 mark) for RTTY on my new ICOM 756PRO, activating the RTTY filter button (on left side of display) or using the internal RTTY decoder completely cancels my low-tones setup and restores 2125 as the default. Is it possible to use low tones with either of the "RTTY Filter" or decoder functions? Jerry W4UK