Source google image: http://revistasebo.com/wp-content/uploads/western-plow-controller-wiring-diagram-to-curtis-truck-side-for-within-4-port-isolation-module-like-d.jpg
4 port isolation module
Source google image: http://revistasebo.com/wp-content/uploads/western-plow-controller-wiring-diagram-to-curtis-truck-side-for-within-4-port-isolation-module-like-d.jpg