{HEAD ~ the preprocessing module} includes an elevator and {TAIL ~ an elevator control} capable of cooperating with the operation of the transport mechanism to position the rack to receive batches of wafers of varying numbers of wafers without empty positions therebetween 
{ HEAD ~ the preprocessing module } includes an elevator and { TAIL ~ an elevator control } capable of cooperating with the operation of the transport mechanism to position the rack to receive batches of wafers of varying numbers of wafers without empty positions therebetween
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