POL is used to specify the polarization of a channel. This may be used when asking SCHED to set a lot of defaults. Or it may be used to tell SCHED the polarization in cases where it is not clear from other inputs. Such cases arise when RCHAN, and LCHAN are not used AND the setup does not correspond to one in the frequency catalog..
POL should be RCP, LCP, or DUAL. One value per channel can be given. Any channels not set will default to the same value as the first so it is usually sufficient to just specify one value. If POL = DUAL for the first channel, SCHED will set alternate channels to RCP and LCP.
Actually, POL can also be R or L (meaning RCP and LCP respectively), but don't tell anyone.