If you turn the OBS or HSI to within 90 degrees of the radial you are on it will tell you you are FROM the station. If you set the reciprocal of your present radial or any setting with 90 degrees of the reciprocal, it will say TO.
a little correction here, if you are +/-80* within the selected OBS radial then "from" is displayed and if +/-80* of the reciprocal of the OBS radial then "to" is displayed.
this leaves a gap of 40*. i.e.10* of either side of +/- 90* of obs radial. if the aircraft is in this zone then you get both or none flags display, depending on the instrument.
hope this helps.