- Johnson RF Coaxial Termination is a passive, single port resistive interconnect device, which is used to terminate the output port/ impedance of a device under test (DUT) or to terminate one end of an RF test cable. These devices can be used in the field, to possibly terminate the unused port of a multiport RF coaxial switch or of a directional coupler. They are commonly used as impedance termination devices in various factory or laboratory Test & Measurement applications.