Termination assemblies for terminating high-frequency data signal transmission lines include housings with one or more cavities that receive ends of the transmission line therein. The transmission line typically includes a dielectric body and a plurality of conductive elements disposed thereon, with the plurality of conductive elements being arranged in pairs for differential signal transmission. The termination assemblies, in one embodiment include hollow end caps that are formed from a dielectric and which have one or more conductive contacts or plated surfaces disposed on or within the cavity so that they will frictionally mate with the conductive traces on the transmission line. In another embodiment, a connector housing is provided with a center slot and a plurality of dual loop contacts to provide redundant circuit paths and low inductance to the termination assembly. A coupling element may be utilized in the slot to achieve a desired level of coupling between the termination contacts.