Coupling method is largely divided into two categories: capacitive coupling & inductive coupling. 

The term “capacitive” means the coupling through a capacitor.  The metal plate of the adaptor and the wires under test forms a certain capacitance by being put into proximity with an insertion of a dielectric material, and actually functions like a coupling capacitor. 

The term “inductive” means electrically the same coupling mode as a transformer.  The circuit in the coupling adaptor works as the primary winding and the cables under test which are surrounded by the adaptor works as the secondary.  The CA-805B is a capacitive coupler and the CA-803A and CA-806 (15-00007A) are inductive couplers.