This schematic depicts all components used in the Rd500lc 1985 1ge Europe 251ge-300e1 Electrical 2 partslist.
A sample from the products for the Electrical 2 include: Servo Motor Assy, Nut, Flange (1j3), Stop Switch Assy, Neutral Switch Assy.
On this parts fiche the Collar is the most specified component.