Create one-to-many to two fields in different table

I have a database where I am trying to figure out how to join a table that contains an object called ModelType. The calibration table contains two fields (EffModel and BkgModel) that are based on a ModelType. I cannot figure out how to join these two fields. Below is an image of the stucture. I am trying to make sure that if I were ever to update one of the model types, that I would not have to update the reference Calibration. I thought about creating a table called EffModelType and BkgModelType, which would separate the two fields depending on the same table but cannot for the life of me think of what would go in it. Updated Info: I may have misspoken about EFFModel and BkgModel Being based on Model type. Essentially an example table model type is as follows: ModelTypeID | ModelName | ModelNumber +++++++++++++++++++++++++++++++++++++++++++ 1 | Linear | 1 2 | Exponential | 2 and the EFFModel will be assigned a model type such as 1 (linear) and the BkgModel will also be assigned a model type, such as 2 (Exponential). Also the ModelNumber is an identifier from another application that will eventually be deleted so it can be ignored.