How do I re-program Stannah Model 420 to recognize "new" remote control?

I been told by a serviceman that settings must be made on the stairlift printed circuit board (PCB) so that a new remote control will be recognized. How is this done?

Background: I have replaced a failed Stannah Model 420 remote control with an identical used unit purchased from eBay. (I have an original second remote control that continues to work correctly.) The PCB does not have any apparent switches or printing about remote control settings, but it does have a yellow block of 3 pins labelled for SWIV and KP where the middle pin is common to each label. Discounting the manufacturers test points, I can find no other locations for making or changing settings.