lots and lots of different types of valves out there  generally though  supply water goes into mixing valve this is where your temp is set or adjusted  then on to a diverter valve  this usually has on off   head 1   head2  and head 1 and head 2     and there are diverters that offer even more options  be sure you have large enough water supply pipes as well as enough pressure  and volume to make the thing work  check this all out first or you may be very dissapointed with the outcome after all that work  and i do mean all that work if you know what i mean!!