rench bit-changing system. Low Points:  Like the P-C 7518, this model’s motor ramped up and down under load trying to maintain the preset speed, and its speed-selector switch is difficult to read in a router table.  You get no 1/4" collet or any dust-collection hoods, although a dust shield diverts chips.  The 7539 is top-heavy, and the stiff plunge action makes fine adjustments difficult.  When mounted in a table (and still under spring tension), coarse adjustments proved difficult unless the insert plate was screwed to the table or held in place by the fence.  The 3-15/32" base opening prohibits the use of larger bits.  No flat edge on the subbase makes routing against a straightedge more prone to slight discrepancies.