With the Service Code Validation set to Department Structure, you can define the valid combinations per Department. On the Department screen, you select a department record and then on the Structure tab, you can associate suppliers (top level), service categories, and service codes (bottom level) in a hierarchical structure. It is not necessary to use all the levels. You can skip the supplier or service category level for example, or you can skip both. Even though it is not necessary to enter a Service Code, it is recommended you do, because the Service Code determines the work to be done and is necessary for both the creation of the work order and possibly a case from the service request.
On the Call Center Setup screen, you can opt to allow the same Service Code with multiple different parents, for example two different suppliers or service categories. To allow this make sure you unselect the checkbox called Use Department Structure Values Only Once.
With Service Code Validation set to Department Structure, the department that is selected on the service request determines the services that can be provided and by whom. This selection can be made even before the equipment is selected. For the remaining two validation methods, the equipment must be selected first.