Brand new in original packaging. Placing a Line IsolatorTM at the output of the transceiver or linear amplifier, prevents RF from traveling along the outer surface of the coax's shield. Of course, the Line IsolatorTM does not affect the signal traveling inside the coaxial cable. The Line IsolatorTM installed in series with the transceiver and linear amplifier helps the transceiver's output filters work effectively by breaking a secondary (leakage) path.
As in the example above, the ground loop path to the linear is eliminated.