Let us say it like this:
A MS will use SCH initially to know the time(TDMA) of network/BTS first.
But before entering into the dedicated mode the MS will be told by the BTS to correct its watch(the one which is to be used for TX)using the given TA.
Also for RX the MS need not to do anything as BTS is taking care of adjusting its watch attached to the particular TS of MS under question.
So, does this mean MS has to use two watches in dedicated mode.